Diesel RV Club, an FMCA Chapter

Ask Dave => Hey Dave, I've Got a Problem => Topic started by: gbarney on April 07, 2019, 10:41:04 PM

Title: Cat 3126, low power, low boost, low fuel consumption
Post by: gbarney on April 07, 2019, 10:41:04 PM
Hi Dave,
You helped me in 2017 with this engine solving air leaks in the Win Racor filter causing stalling and apparently overheating, and later with a faulty injector electrical harness plug that was causing loss of #3 injector. Both of these problems seem solved, but I am still unhappy with the engine power.

This engine ran great when I bought the rig in Jan. 2010 in Arizona and drove it to Seattle. Had no problems climbing the 6% grades on I-5 in northern CA and OR. Downshifted to 5th on some, but easily maintained 60mph. Summer of 2010 I took the rig to the local Cat shop for oil and filter change. I don't think it has run right since.

The engine serial # is 1WM10006, installed in a 1997 Safari Continental with aprox 85K miles. It starts easily, runs smooth, no codes, no smoke, no oil or coolant use, just not much power.

I have had the rig on a Cat shop dyno. Dyno shows 250hp at the wheels. Tech claims the 80hp drop from 330 rated hp was "parasitic loads - fan, water pump, transmission, ect. I think that's BS. Things that were checked:

Air intake system for air leaks, none found.
Exhaust system leaks, none found.
HEUI oil pressure, OK
Fuel pressure, OK
Injector cut-out, at idle and under power, OK
Turbo spinns freely
Pac brake valve is fully open
Reflashed ECM
Maximum boost pressure, 23PSI.

Shop recommeded replacing injectors, HEUI, turbo, fuel pump, filters again, and a few other parts adding up to about $20K and if that didn't solve the problem consult with factory. I declined.

I called the Cat 3127 help line. They looked up the original test stand specs for this engine, boost pressure was 56.4 inches of mercury. That converts to 27.7 PSI. This is what I recall from when I first drove the rig in 2010. This rig has one of the Safari Intelidrive electronic engine monitors that still works. This unit taps into the J1939 and displays data from the ECM. I also recall from 2010 that at full boost pressure on a grade, the instantenous fuel consuption would reach 1mpg. Help line also apparently has a record of when ECM has been flashed or updated, dates corresponded with times I've had the rig in a Cat shop. It was the correct program for my serial number, and for a 330 hp engine. First recorded update was the summer of 2010, the last time this engine ran well. Help line stated that ECM program doesn't limit or control engine power or boost pressure anyway, so software couldn't be the problem.

I recently made the trip from Apache Junction to Winslow AZ, up HWY 87. This HWY has some 6% and 7% grades on it. Rig weight is about 28K lbs., and I'm towing a Jeep Grand Cherokee - not overweight. Rig rolls freely, no draging brakes. I cannot maintain 2000 RPM in 4th on a 6% grade, maximum boost on direct reading dash gage in 22 PSI, maximum boost on Intelidrive, from ECM, is 18 PSI. Not sure why there is a discrepancy between the two indicators. I have not noticed this in the past. Instantaneous fuel consumption was 2 mpg, so about half what it was in 2010. To maintain 2000 rpm for cooling (it was over 80 degrees) I have to downshift to 3rd, giving a maximum speed of 37 at redline rpm. On the 7% grades, have to downshift to 2nd, run at WOT, 25 mph, cannot reach redline rpm, same boost pressures as in 3rd and 4th.

No issues with overheating though, so that's some good news.

I dont have the equipment to see what is in the ECM program, or how it is responding in real time. There could also be a bad sensor or other issue sending bad data to the ECM. I can change or test minor parts if I know what I'm looking for. I'm not willing to spend $20K to have a CAT shop randomly change parts, trouble-guessing at the problem. I could buy another rig for that money, or a complete properly running for much less.

If you have any suggestions for me, anything would be appreciated. You were spot on with your previous help.


Title: Re: Cat 3126, low power, low boost, low fuel consumption
Post by: David.e.atherton on April 08, 2019, 03:58:01 AM
Glen, there are several questions that I have relating to your problem and the information
from your scan gauge plugged into your J-1708 data port. To late many RV people seem to be using that J-1708 data port ( which sole reason for its placement is a test port to support
Caterpillar ET testing equipment ). as a house hold electrical outlet. Yes there is a different
readings between the Caterpillar ECM and aftermarket add on equipment. That is where
We will start on your problem, can you email all the Caterpillar data you have from your visit
with Caterpillar after the test on the Dyno. Ask Dave, Dave Atherton Retired Cat Mechanic
Title: Re: Cat 3126, low power, low boost, low fuel consumption
Post by: gbarney on April 08, 2019, 09:16:43 PM
Hi Dave,
Attached are the Cat service notes from the dyno test. There isn't much information here, most of the time was spent either working on the CAT test equipment or trying to keep the engine from overheating, so a proper PAR was never completed.
I also attached the manual for the Magnum Intellidrive. This isn't an aftermarket scan tool, and isn't plugged into the test port. These units were factory installed in the dash by Safari, and are hardwired into the datalink backbone. It is a read only unit, with no capacity to modify or control ECM programming. I think the company that supplied these units to Safari now produces the Silverleaf Engine Monitor, which is an aftermarket add on and has a lot more capability.

Title: Re: Cat 3126, low power, low boost, low fuel consumption
Post by: David.e.atherton on April 10, 2019, 05:18:11 AM
Glenn, you must admit climbing north to flagstaff most motorhomes are not In a better shape
As you indicated. We were on same road not long ago with a motorhome with Cummins ISL
400 hp. Climbing the steep grades yes we were 35, 30 and lower pulling a car travel that same route many time that is the nature of the beast. Can you tell me if you on your code reader
If you have a code 173-0 and 173-00 and posbile answer to your problem being your engine
Is not over heating on temperature gauge. Looking at your engine S/N number your engine
Is a cat reman engine. Boost pressure 23 psi is your correct boost for your engine. One
thing you keep talking power loss I think understanding how boost pressure runs packing
more air into engine along with more fuel under load ( the fuel Fate Control is set at factory
and will not deliver any more fuel to your engine regardless of how high your boost pressure
Indicator reads.) another area comes into play what is your engine rpms reading at the
time of pulling the steep grades. I’m very interested in the temperature being maintained
as you indicated engine not heating up . Ask Dave, Dave Atherton Retired Cat Mechanic
Title: Re: Cat 3126, low power, low boost, low fuel consumption
Post by: gbarney on April 10, 2019, 06:05:14 PM
Hi Dave, thanks for the response. I don't think this is just the nature of the beast. I make frequent trips between Seattle and Sacramento on I-5 through the mountains in Oregon and northern CA. Many of those grades are 6%, and while I am running at WOT other RVs are easily passing. Many of them with the same Cat 3126, or the Cummins 8.3, as I can see the logos on the back as they pass. Some are even towing crew cab pick ups, or large cargo trailers. Even the gas rigs with V10s and 454, towing heaver cars, boats, or trailers than I am have no trouble passing.

I don't have a code reader, I'm just checking flash codes. All I get is the 55 code indicating no DTCs. Maybe I need to buy a code reader, do you have any recommendations?

I am in Cottonwood AZ now, and I was monitoring both the boost pressure gauge and the Intellidrive electronic readout boost pressure on the way here. There seems a pretty constent difference of about 3 psi between the two. Since the electronic readout is direct from the ECM I think it is more relevant. It never exceded 20 psi, and was mostly 18 or 19 psi at WOT with RPM 2000 to 2400. The boost pressure gauge showed 3 psi higher.

As to engine coolant temperature, it does heat up when the engine is under load. I only intended to say that it doesn't overheat as long as I keep the engine above 2000 RPM. On the level, coolant temp runs between 180 and 190, with the temp gauge and Intellidrive electronic readout matching. Under load on a long grade, it can run between 200 and 215, but it will stabilize.  On a cool day I can let the engine lug down in 4th and the coolant will still be OK, but if it is warm out I have to force the trans down to 3rd to keep the RPM above 2000, or it would likely overheat. I've let it reach 220 before downshifting, but once I do the coolant temp will drop back below 215 and stabilize.

Title: Re: Cat 3126, low power, low boost, low fuel consumption
Post by: David.e.atherton on April 11, 2019, 05:29:39 AM
Glenn, thank you we are starting to figure out where problem is. You indicated engine temperature running between 180 and 190 area normal driving and 215 on grades.
What all this is means your engine ECM is keeping your engine locked in what is called
Startup cold mode. This will be reinforced with very low intake temperatures. Note: your
caterpillar temperature regulator starts to open at 191 deg f and full open at 206 deg f.
I going to be tied up today to pull technical information. Assuming that you are using a
Caterpillar temperature regulator it could be installed incorrectly with jiggle pin in wrong
Position in the regulator housing or jiggle pin is missing. Temperature regulator could have
Came apart  or stuck open. Or if not Caterpillar regulator and aftermarket part house part
The value of regulator is different. The way you gave me the present information your
Temperature regulator has not opened or stuck opened. Ask Dave, Dave Atherton Retired
Cat Mechanic
Title: Re: Cat 3126, low power, low boost, low fuel consumption
Post by: gbarney on April 11, 2019, 09:07:02 PM
Hi Dave,
Interesting comment about the regulator not performing properly, and the ECM locked in cold mode. I replaced the regulator in 2014 with a CAT part, and the coolant, hoping it would improve the engine overheating problem. It didn't seem to have any effect. The regulator was either changed or checked by a CAT shop again in 2017 during trouble shooting for engine overheating. Again there was no improvement. I don't have any problem with changing it again if you think there could be a problem with it. There is a CAT dealer nearby where I should be able get a replacement regulator.
I didn't know an ECM could become "locked" in cold mode, but admittedly there is a lot I don't know or understand about these engines. If it is locked, then the next question is, how do I get it unlocked?

I'll be here until middle of next week, so no big rush as I know you are busy. Please let me know what you recommend next when you can.

Title: Re: Cat 3126, low power, low boost, low fuel consumption
Post by: David.e.atherton on April 12, 2019, 04:29:45 AM
Glenn, the cold mode will reduce power without smoke at exhaust and will stay in cold mode
as you indicated while driving down the road. If the temperature which you posted for sure
correct we need to find out why. Will get with you with technical information and suggest
direction you may want to take. Ask Dave, Dave Atherton Retired Cat Mechanic
Title: Re: Cat 3126, low power, low boost, low fuel consumption
Post by: Journey on April 12, 2019, 09:12:27 AM
  Dave I seem to be in the same situation. Temp running at 186. Where should the jiggle pin be in relation to the housing?
Title: Re: Cat 3126, low power, low boost, low fuel consumption
Post by: David.e.atherton on April 12, 2019, 01:35:01 PM
Journey, will get back with both of you with more detailed information on running in
what is called the cold mode. Ask Dave, Dave Atherton Retired Cat Mechanic
Title: Re: Cat 3126, low power, low boost, low fuel consumption
Post by: gbarney on April 12, 2019, 06:40:38 PM
Hi Dave,
I ran a little test on the regulator this morning. Basically just started the engine and monitored the coolant temperature during warm-up. Following are the results:
Outside air temp: 59 degrees
Starting coolant temp: 59 degrees
Cold Mode: Off (as reported by "Engine Status" panel of Intellidrive)
Fast Idle: for about 30 sec. after start, then 700 RPM

Idle time     /   Coolant Temp
20 min.       /   152 deg.
25 min.       /   163 deg.
30 min.       /   172 deg.
35 min.       /   179 deg.
40 min.       /   187 deg.
45 min.       /   181 deg.
50 min.       /   181 deg.

Until about 43 minutes the air exiting the radiator remained cold. At that time the regulator appears to have opened and the coolant temp droped to 181 in less than 30 seconds. After that coolant stabilized at 181 degress and the air exiting the radiator was warm.

During a normal warm-up, while driving slowly, engine reaches 187/188 within 10 minutes, then drops to 181, following the same pattern as above but in a much shorter time.
Based on the above, the regulator appears to functioning normally, possibly a little slow to open initially, and the Intellidrive reports Cold Mode is off.

May have to look elsewhere for the cause of the low power problem.

Title: Re: Cat 3126, low power, low boost, low fuel consumption
Post by: gbarney on April 16, 2019, 08:41:41 PM
Hi Dave,
I haven't heard back from you on steps to investigate the possibility of ECM locked in Cold Mode. However since the regulator seems to be operating normally, and the IntelliDrive is reporting Cold Mode: Off, this may not be the problem.
I wanted to verify that I had accurate boost pressure indication because the analog dash gauge was reporting 3 psi more that the ECM was through the IntelliDrive, so I replace the boost pressure sensor to see if there would be a change. There wasn't. Based on this I must assume now that the lower ECM/IntelliDrive indication is correct and the analog gauge is incorrect.
I left Cottonwood this morning headed north on I-17 to Flagstaff AZ. There are several long 6% grades on this route. Highest boost pressure reached was 20 psi, and that was infrequent. Mostly 18 / 19 psi., in 4th gear, for as long as RPM was still above 2000. Maximum fuel consumption rate was 2 mpg, briefly, but mostly 3 mpg at WOT. This is an engine that used to routinely go to 1 mpg at WOT. On all these grades, I was eventually forced to downshift to 3rd after RPM decade below 2000 and coolant temp headed toward 220. In 3rd engine rpm is at redline, speed is 37 mph, and coolant temp will stabilize.
Last year when this rig was on the Dyno, fuel rail pressure was 75 psi with no bubbles in the return line, and the HEUI oil pressure was 3300 psi. So there is fuel available to the injectors, and oil pressure available to power the injectors, so appears that the ECM is limiting the amount of fuel injected for some reason. Any thoughts on what to check next?
Title: Re: Cat 3126, low power, low boost, low fuel consumption
Post by: David.e.atherton on April 16, 2019, 09:09:15 PM
Glenn, cannot really understated problem one time we are posting no heating problem,
than now your posting heating problem on grade. Been very busy and have not had chance
to get into technical issues. Maybe you should compare your code reader to Cat ET and
Take Cat technical information and stay with Caterpillar. I would get another opinion from
Caterpillar because if you feel your scan gauge code reader information is taking you
away from if there is really something going wrong and Cat  ET will address your problem.
at this point getting second thoughts from Caterpillar think you should listen to what is
being offered from therm. Ask Dave, Dave Atherton Retired Cat Mechanic
Title: Re: Cat 3126, low power, low boost, low fuel consumption
Post by: gbarney on April 18, 2019, 09:49:53 AM
Hi Dave,
Thank you for your thoughts. I do understand that you are busy with a project, and the problems I am having are not urgent. The coach does run, and I am headed back to the NW for the summer. It will be at least another month before I will have anymore time to devote to this myself.
It is interesting that you are thinking I still have an overheating problem from the coolant temperatures I was posting. I was simply trying to provide as much information for you as I could on all the operating conditions as I could, not suggesting an overheating problem. I was satisfied that there was a way, following the chassis manual recommendation, to have the coolant temperature stabilize anywhere within the normal operating range. That wasn't the case in the past. The fact that I have to downshift all the way to 3rd to maintain 2000 rpm is the result of low engine power output, which is the issue I've been trying to resolve.
As for further work with Caterpillar, I think I've pretty well exhausted that avenue. There are no trouble codes, and all the component tests they can perform are OK. The Dyno did confirm I am only getting about 250 hp. Next recommended steps from the shop is to just start replacing components, starting with injectors, to see if something changes. After they have replaced everything on the engine, if performance isn't improved then contact Caterpillar engineering for further assistance. This is way to much money to spend without any assurance of success. For less money, and a more certain outcome, I can trade this coach in on one with a better running engine. I've just been trying to avoid that option.
If you do have time later this summer to send me any suggestions, we can pick this up again then.

Title: Re: Cat 3126, low power, low boost, low fuel consumption
Post by: ziggyh on April 18, 2019, 06:09:40 PM
Gbarney, have you checked to see if you have any exhaust restriction beside the prac break.
Title: Re: Cat 3126, low power, low boost, low fuel consumption
Post by: gbarney on April 19, 2019, 09:55:13 AM
Hi Ziggy,
Thanks for the suggestion. I've thought about this some but never actually tested it. At idle there seems to be free flow, as you can detect individual pulses from each cylinder. However at higher air volume it could be building up back pressure, so perhaps worth checking once I get back up north for the summer.

Title: Re: Cat 3126, low power, low boost, low fuel consumption
Post by: ziggyh on April 20, 2019, 05:21:00 PM
Glenn, cat should have a max back pressure spec for your engine. If not I am only guessing that 3"Hg under full load would be max. That I would want to see. 1"Hg is equal to 13.6"H2O if you are using a slack tube manometer.
It might just be easier to just drop the muffler.
Title: Re: Cat 3126, low power, low boost, low fuel consumption
Post by: gbarney on June 29, 2019, 12:38:32 PM
Hi Dave,
I hope this finds its way to you as it has been a couple of months since I was last in contact. You were busy with a project at the time, and I need to return to the Seattle area and attend to some projects of my own.

I have done a couple things since then. I replaced the manifold sensor since there was a disparity in the readings between the electronic readout on the Intellidrive from the ECM and the analog dash gauge, with the analog gauge reading 3-4 lbs higher. There was no change in manifold pressure reading from the ECM, so I am concluding that the sensor was accurate. This also means that my maximum boost pressure is 21 lbs.

Also as suggested by Ziggy I made a very basic check for muffler backpressure, using air supplied from an electric weed blower. Lots of air through the muffler, no detectable backpressure.

In your previous comments on this thread, you mentioned providing some information on how to check that the ECM is not somehow stuck in "cold mode." The Intellidrive Engine Status screen shows "Cold Mode Status: Off", but who knows. If there is another was to verify this, I would be interested to know.

Other than that, and based on you last suggestion to just follow the Cat service shop recommendations, I think I'm at the point of replacing all the injecters to, as the service shop put it, "just to make sure that isn't the problem."
Title: Re: Cat 3126, low power, low boost, low fuel consumption
Post by: ziggyh on June 29, 2019, 02:41:11 PM
Glenn. I’m not so sure that a leaf blower has the same volume of flow as your engine. I would check the back pressure while driving at highway speeds by drilling a small hole in the exhaust pipe before the muffler/converter and measuring with a manometer or as cat service procedure at a high idle x1.8 of the reading. 
Title: Re: Cat 3126, low power, low boost, low fuel consumption
Post by: gbarney on July 02, 2019, 07:18:55 PM
Hi Ziggy,
Thanks for your response. I admit that my test wasn't very precise, and really wasn't intended to be. I was really only looking for any indication of back pressure that would justify a more comprehensive test. There just wasn't any such indication. Air passed through the muffler like it was an open chamber. Partially blocking the tail pipe would create backpressure quickly, but otherwise - nothing.

My focus is on the injectors, as this is what the Caterpillar shop recommended changing after the Dyno run. This engine had a HEUI pump replaced a couple years ago due to very low boost, wouldn't get over 10 psi and even that took for ever to build up to. Replacing the HEUI pump didn't improve performance at all, although the shop continued to insist that the pump was bad and shedding metal particles. After that, replacing the air filter increased the engine performance to where it has a max boost pressure of about 21 lbs., but never to the original boost pressures. I didn't put much stock in what the shop was telling me at the time because their recommendation to replace the HUEI didn't solve the problem I was having.

From what I've read since then, metal from a failing HEUI pump frequently contaminates the injectors resluting in poor engine performance. So, perhaps the shop that replaced the HEUI pump was right and the pump was failing and contaminated the injectors.

I was kind of hoping that David Atherton might come back on line with further comments or suggestions, but he may not be currently available. He has been of great help to me in the past and I value his opinions.
Title: Re: Cat 3126, low power, low boost, low fuel consumption
Post by: ziggyh on July 02, 2019, 08:28:57 PM
Glenn, by chance have you had cat et hooked up while driving and looked to see if you are reaching the rated fuel limit. Also is the APP or accelerator pedal position sensor reading wide open throttle when fully depressed.
There is also a possibility that something on the data line is limiting power. That status is also indicated in cat et. When I return home I will post some screen shots of et data with explanation
Title: Re: Cat 3126, low power, low boost, low fuel consumption
Post by: gbarney on July 03, 2019, 01:58:31 PM
Hi Ziggy,
Not hooked up while driving, but it was hooked to the CAT ET while on the CAT Dyno. They weren't able to identify any problems, codes, etc., other than low power and high coolant temp. Dyno was showing 250 hp at the wheels. They wrote off the other 80 hp as parasitic losses, cooling fan and such. I wasn't buying the idea that 80 hp, or anywhere near that, was getting transmitted across that fan belt.
Title: Re: Cat 3126, low power, low boost, low fuel consumption
Post by: ziggyh on July 04, 2019, 07:58:07 PM
I have seen 35Hp drop off on a dyno when the cooling fan kicks in. Alternator, water pump, power steering and a\c will siphon of some as well. If the engine was running hot perhaps the intake air temp was getting a bit high and that may cause some decrease in performance.
Title: Re: Cat 3126, low power, low boost, low fuel consumption
Post by: gbarney on July 08, 2019, 09:20:06 AM
I shipped the injectors off to a rebuilder Friday. It will be a couple weeks before I get them back and have time to reinstall them. I'll let you know the outcome.
Title: Re: Cat 3126, low power, low boost, low fuel consumption
Post by: ziggyh on July 08, 2019, 07:11:21 PM
Thanks, would like to know the out come, good luck.
Title: Re: Cat 3126, low power, low boost, low fuel consumption
Post by: gbarney on July 25, 2019, 05:32:58 PM
Rebuilt injectors returned and installed. Rebuilder reported finding "metal chips" in the injectors.

Engine cranks but will not start. Initial check shows there is no oil from the HEUI pump. Not just no, or low, pressure, no oil at all. Engine oil level is in the operating range, engine oil pump builds slight pressure on dash gage while cranking, enough to turn out the low oil pressure light. I pulled the test port plug on the HEUI oil gallery in the head, no oil present in the galley. This was after a total of 15 to 20 minutes cranking time (30 sec. crank / 2 min. cool intervals).

I will try to get a pressure gage on the HEUI output line tomorrow just to verify.

Expect I will be buying another IAPCV, or another HEUI Pump, or both.
Title: Re: Cat 3126, low power, low boost, low fuel consumption
Post by: David.e.atherton on July 27, 2019, 08:21:49 PM
Hi , what are you doing ? Kinda sorta following your post. Question service repair shop,
Caterpillar dealer or service shop that worked on your engine. What is happening there
is no engine oil being pushed to the Heui pump from oil pump ln oil pan. Possible reason
air locked at oil cooler check valves.column of air in system will not open the check valves
In oil cooler. Next question disconnect hot 12 volt wire going to engine intake heater and
try starting with starting fluid. Engine will light on starting fluid but not stay running. Your
Problem first with no start ( Injection Actuation Pressure Sensor ) disconnect the IAP Sensor
engine should start and run at idle but no power. What that is telling you the IAP Sensor
is bad. If Connect Cat ET you should have a event code 164-4 or 164-7 . No luck than go
next to the Injection Actuation Pressure Regulaor and Cat ET Code or 42-11 Injection
Actuation Pressure Regulator Fault.. what that is telling you the Injection Actuation Pressure
Regulator is not letting the high pressure engine to the injectors. Or the electrical connection
Is not getting to the Solenoid on the regulator. That is where you need to go to make engine
run. Before anything make sure engine oil pump in oil pan the relief valve is not stuck open on oil pump, and second make sure engine oil is bleed at both of the oil cooler check valves.
Ask Dave, Dave Atherton Retired Cat Mechanic
Title: Re: Cat 3126, low power, low boost, low fuel consumption
Post by: David.e.atherton on July 27, 2019, 08:56:29 PM
gbarney, just add information than may be of help deeper into your problem . You
mention metal chips at injectors screen. It would be my first order of action pull
A oil sample and send out ASAP. Metal floating around in engine oil galleries will
Spell engine failure and it just may be happening right now at engine oil pump in
The oil pan engine oil pump failing and milling of metal first caught up in oil pump relief
Valve is possible for no engine oil to Heui pump. Taking that oil sample will identify
the metal being floating within the engine oil galley. I would also cut open the engine oil filter
To see amount of steel milling present. This information is your first line of defense to
access the extent of travel metal in the oil galley. I do believe I have mentioned oil sampling
before along with others and with out question will pin point what is not working.
Ask Dave, Dave Atherton Retired Cat Mechanic
Title: Re: Cat 3126, low power, low boost, low fuel consumption
Post by: gbarney on July 27, 2019, 11:42:13 PM
Hi Dave,
Thanks for responding, glad to hear you have been following along.

No shop involved in this project. Just about fed up with paying shops (including Cat shops) $100+/hour to make mistakes. As the song says, "I can make mistakes myself just fine."

Anyway as a recap, other than never making full power this engine was running just fine up until I removed the injectors. Drove it to Arizona last winter, stayed at multiple locations, then back to Seattle this spring. Always starts right up, runs smooth, no stalling or other problems other than lack of power.

Back in 2014, also in Arizona I encountered had encountered severe loss of power, very little boost pressure and what would build took a long time. From a standing start at WOT, maybe half a city block before any boost would register on dash gage. Changing fuel filters didn't help. An independant shop checked it out and said the HEUI pump was failing. HEUI pump was changed, but there was no improvment. Shop swore up and down that pump was bad, that metal was comming out of it. I lost confidence in them, so I took it to the nearest CAT shop, which told me the IAPCV should have been changed before the HEUI pump, since HEUI pumps rarely fail. So they changed the IAPCV, still no improvement. After some more $100+/hr troubleshooting, they decided that the air filter was plugged. After the air filter was replaced, engine performance significantly improved but never back to what it had been prior to this problem.

Now five years and at least 20,000 miles later, it has been in CAT shops multiple times, and been on the dyno, trying to find out why it still doesn't run the way it did before the issues in 2014. Cat shops can't identify a fault or problem, but would be happy to start replacing parts, startng with injectors, just to see if something changes.

So, not having found anything else and reading multiple accounts of HEUI pump failures resulting in metal contamination of injectors, I'm thinking that perhaps the independent shop in 2014 was correct about the HEUI pump failing and perhaps sending metal into the injectors, even though the plugged air filter was the immediate problem. This is why I decided to pull the injectors and send them to a rebuilder. It was the rebuilder that reported finding "metal" inside the injectors. I did not see metal on the outside of the injectors, nor did I see any screens. This is a 1WM series engine, 3126"A", I think it is referred to as. It has the side solenoid injectors, and cross-over tubes that feed HEUI oil to the tops of the injectors. I think screens were on the later model injectors.

I haven't found any trace of metal in the engine oil, on the dip stick, or in the rocker box. After removing the injectors, I removed the rear plug from the HEUI oil gallery in the head and flushed it with brake clean to ensure there weren't any metal filings or chips in it. Again, no metal found.

After reassembly with the rebuilt injectors, it would not start. I removed the test port plug on the HEUI oil gallery and found no oil in the gallery. Cranked engine with the plug removed, still no oil in gallery, so no sense in trying to check HEUI oil pressure since there is no HEUI oil. Unplugged the IAP sensor, so ECM would try to go to default HEUI oil pressure, still did not get any oil in the gallery. Engine oil pressure seems fine, oil light goes out while cranking, and oil pressure gage on dash responds, showing 5 to 10 lb. So the oil pump seems to be picking up oil from sump and pressurizing the lubrication system.

Nothing on the engine has been touched below the rocker box up to this point. No reason for loss of oil to the HEUI pump, or air pockets in oil at the oil cooler check valves, or any other such oil issues. This engine can sit for months and then fire right up without a problem. It only sat for barely two weeks with the injectors out.

I removed the rocker cover and rechecked the cross-over tubes and fittings for leaks. Nothing seen.

Next I checked out the IAPCV. First the coil, resistance was good. Then power to it from the ECM, 4V at Key-On, jumping to 9-10V while cranking. So replaced IAPCV with new unit. While it was removed, cranked engine just to see that oil was actually coming out of the HEUI pump - it was, lots of it. Check the oil for metal, none found. After installing new IAPCV, cranked engine and still no oil to the HEUI oil gallery in the head. So I removed the oil line from the HEUI to the head, drained it and check that it was clear, then reinstalled to the HEUI pump only with the open end pointed down into a drain bucket. Cranked engine, strong stream of oil sprayed into the bucket. Reattached the oil line to the head, still had the oil gallery test port plug removed, and cranked the engine. Oil gallery quickly filled the gallery and flooded out the test port. Great! Finally have oil. Reinstalled the test port plug. Engine cranks, still no start.

Cracked the fitting on fuel pressure regulator at back of head and ran purge pump to check for fuel in head. It has fuel.

I can try to find the oil cooler check valves you mentioned and see if there is oil present there.

It will be Monday before I can get a 5000 psi gage and fittings to check HEUI oil pressure. And maybe some starting fluid.

Any other thoughts or suggestions you may have are welcome.

Title: Re: Cat 3126, low power, low boost, low fuel consumption
Post by: David.e.atherton on July 28, 2019, 05:52:33 AM
gbarney, well that information would have helped in this problem with your first post. This is now where you need to go. Remove the Injection Actuation Pressure Sensor remove from engine,
Than install a pressure gauge into that IAP open port. With pressure gauge in place crank
engine over and you will need to get pressure reading of 870 psi before engine will start.
After engine start up engine oil pressure at test gauge should go 3,500 to 4,000 psi. There is
no in between readings that mean anything at this point. Note: this is high pressure oil
From Heui pump that test gauge is reading. Going back to first injectors replacement any time
injector or injectors been removed you have to bleed air from check valves at engine oil cooler.
Back at test pressure gauge and correct 870 psi reading of which engine should start look
at your exhaust discharge and you should start seeing white smoke exiting exhaust . Again
If you have followed my first post disconnect 12 volt power from intake heater and while turning
Engine over give little shot of starting fluid and engine should start and idle. If engine will
Only run on starting fluid go back and read first post again. Do you have any diesel fluid
returning back to fuel tank in front if answer is no remove hose on the return fuel pressure
Regulator and turn over engine like you want it to start. Basic from what your now telling
me your system is air locked engine oil and diesel fuel.
Ask Dave, Dave Atherton Retired Cat Mechanic
Title: Re: Cat 3126, low power, low boost, low fuel consumption
Post by: David.e.atherton on July 28, 2019, 06:19:52 AM
gbarney, I can understand that you want to get your Diesel engine running but you
need to understand without correct technical information and training you can go just so far.
Normally I will not suggest use of starting fluid to untrained Mechanic. In your case and make no mistake about it if you do not remove the 12 volt power wire to the engine intake heater
Your problem will get very big in just a few seconds. The reason for giving engine a little
shot of starting fluid it will spin engine and exhaust all air where starter will crank slower .
and if engine will run only on starting fluid assist that means replacement of the IAP Sensor
Or the IAPR valve.  Troubleshooting your problem would be located in these to parts. Last
With valve cover off and looking at each injector while cranking engine over look for air oil
Bubbles at injector base of each injector for oil leakage you may have o-ring twisted or cut.
This is about all I can assist you with. If you had Cat ET connect at this point you would see the event code I posted on my first post. Ask Dave, Dave Atherton Retired Cat mechanic
Title: Re: Cat 3126, low power, low boost, low fuel consumption
Post by: gbarney on July 28, 2019, 10:39:39 AM
Hi Dave,
Thanks so much for the info on bleeding air from the filter check valves. Air lock related to having the injectors removed makes much more sense than a random failure of either the HEUI pump or IAPCV during the time injectors are removed.

Took a look at the oil filter housing. I see one plug on the housing just above the oil filter, and another on the top of the housing, near the block, and a few inches toward the front (fan end) of the engine from the oil filter. Are these the two ports for the check valves? To get air out can I remove the plug, and presumable a spring and steel ball, then crank the engine until air is exhausted and oil exits the open port, then reinstall check valve, spring, and plug? If so, should one be done before the other, or both at once?

If I still need to try starting fluid, I will definitly remove power from the manifold heater first.
Title: Re: Cat 3126, low power, low boost, low fuel consumption
Post by: gbarney on July 28, 2019, 09:55:41 PM
Hi Dave,
Sending an update from today.
1. Engine started using the starting fluid, ran for a minute or so until the starting fluid can was empty. Would not restart afterward.
2. Removed upper cap on oil cooler check valve, cranked engine until oil flooded out. Only took a few seconds. Reassembled popet, spring and cap.
3. Loosend cap on oil cooler check valve near the oil fliter, cranked until oil was leaking from the threads, then re-tightened cap.
4. Tried again to start engine, no start.
5. Opened oil inlet pipe connection at HEUI pump and cranked engine. Oil flooded out. Reassembled connection.
6. Opened test port on HEUI oil gallery in head. Cranked engine. Oil flooded out. Reinstalled test port plug.
7. Cranked engine, no start.
8. Disconnected three wire plug for IAP sensor.
9. Cranked engine, no start.

Tomorrow is Monday, I should be able to rundown a 5,000 PSI gage and connection hardware to test HEUI oil pressure.

Title: Re: Cat 3126, low power, low boost, low fuel consumption
Post by: David.e.atherton on July 29, 2019, 04:11:24 AM
gbarney, what you just tried and engine will not run is the Injection Actuation Pressure Regulator
Is not opening. The engine will not run until high pressure Heui pump oil operates the injectors.
The use of the starting fluid just reniforced that because engine will not stay running on its own.
Next question are your sure you have power 12 volt going to your ECM that would be pin 40
red wire that is a on/ off key switch . Do not assume anything at this point, the information
I been providing there should be Power to ECM and working within Engine itself. Anyway
You will need power to ECM.than power to IAPR Regulator than 870 psi oil pressure and
engine should run if everything you preformed is correct. Do not use anymore starting fluid
Understanding that you used a complete can that not what I said just a little starting fluid.
Ask Dave, Dave Atherton Retired Cat Mechanic
Title: Re: Cat 3126, low power, low boost, low fuel consumption
Post by: gbarney on July 29, 2019, 08:57:47 AM

Thanks again for staying with me on this. Its extremely frustrating and I'm tearing out what little hair I have left.

I have power to the ECM, check engine light comes on for 5 seconds at Key On. I get flash code 5-5 when checked as long as I don't have something unplugged.

I checked power at the 2 wire connector for the IAPCV. I got about 4 volts at Key On, and it jumped up to 9-10 volts while cranking.

After this check, I also thought IAPCV must be bad, bought a new one and installed it. Still didn't start or change anything.

I've also cranked engine with valve cover off looking for possible oil leaks at cross over tubes and injectors. Didn't see any leaks. Seems like there is oil flow HEUI Pump as long as it doesn't have to build up any pressure. This would indicate a bad HEUI Pump, but I want to see it on a gage before spending $1400 on another rebuilt pump. Doesn't make any sense either that a HEUI pump would just go for working fine to failed while sitting for two weeks while the injectors were out.
Title: Re: Cat 3126, low power, low boost, low fuel consumption
Post by: David.e.atherton on July 29, 2019, 05:59:42 PM
gbarney, guess when you install test gauge into system you will know cranking if engine will start. One question, your injectors Cat new , Cat reman or aftermarket ingectors. No high
pressure engine oil to injectors to start , Injection Actuation Pressure Sensor possible bad,
Injection Actuation Pressure Regulator has voltage at solenoid but undetermined if the valve
Is opening or stuck because engine will not start if no high pressure engine oil. Return fuel check valve air in system. Note: there has been many HEUI pumps changed out because
Low engine oil pressure or no oil pressure. Do not assume that you replaced Injection Actuation Pressure Regulator that that cannot be the no start problem. Without a oil sample you are just
Guessing anything is possible. Point to remember again if you cannot get high pressure
engine oil to the injectors via. IAP Regulator your engine will not start and run. The starting
fluid told you that will run on starting fluid. Take you right back. to the sensor and regulator
Ask Dave, Dave Atherton Retired Cat Mechanic
Title: Re: Cat 3126, low power, low boost, low fuel consumption
Post by: gbarney on July 30, 2019, 05:14:51 PM
Hi Dave,
I got the pressure gages (5k and 100 psi) got them hooked up and found my problem. With the 5K gage hooked to the HEUI gallery in the head, it showed no pressure with IAP and IAPCV electrical connections hooked up, or with the IAP disconnected, or with 12v jumped directly to the IAPCV. I did the same checks with the 100psi gage and was reading about 100psi.

I then dead-headed the HEUI outlet line directly to the 5Kpsi gage, expecting the same readings. However I got 4,500psi. So great, the HEUI pump is good and the cause of the low pressure is isolated to an oil leak somewhere in the rocker box.

I removed the rocker box cover for about the 4th or 5th time now to check again for oil leaks. This time I reinstalled the intake cross-over tubes so as to be less concerned about cranking the engine with the intake system open. With the intake system closed, I cranked the engine long enough to find the oil leak. There was a flow of oil from under the head of one of the injectors, from its oil exit port.

I called the injector rebuilder and discribed the problem, and they immediately said they were sending me another injector. It should be here tomorrow or Thursday. I'll let you know how it goes when I get it back together.

This is an independent rebuild shop, R S Diesel Injector Service in Bellflower CA. I was looking for a shop that would rebuild my injectors rather than exchange for injectors with unknown histoy that could have other problems, and that is what this shop does. They have good customer reviews. Looks like I'll still end up with one injector that wasn't orginal to this engine. However after looking at my injector serial numbers, it looks to me like one must have already been replaced anyway. Maybe it really doesn't make any difference. The good part is that the shop reponded quickly to rectify the problem.
Title: Re: Cat 3126, low power, low boost, low fuel consumption
Post by: David.e.atherton on July 31, 2019, 02:52:59 PM
gbarney, yes look at my post above asking about the injectors installed. Many things happen
In troubleshooting and assume that just because I installed this part I will move on and keep
taking parts off. Now that you feel that pin point to faulty injector from rebuild shop this is not
good. Someone was sleeping and injector set now I would question . Reason yes rebuild
Injector if it passed final test before you picked it up and now problem with injector failed and
no start ( think I would pull every injector and recheck at your rebuilder to retest and be
sure your injectors are all to cat spec’s ). Next route I would take and I can tell you are not a
Caterpillar fan but connect Cat ET to your engine and cut out and verify correct injectorl pressure
With engine running. Remember is value of fuel is correct with injector firing you are digging
A very deep hole leading to engine failure. I can only provide advice but that is your choice
as direction taken. Ask Dave, Dave Atherton Retired Cat Mechanic
Title: Re: Cat 3126, low power, low boost, low fuel consumption
Post by: gbarney on August 06, 2019, 08:28:18 AM
Hi Dave,
Couple of days late but the replacement injector arrived yesterday afternoon. Seems USPS lost track of the shipment for a couple of days.  Anyway, installed the replacement injector. It appears to be a CAT Reman. Engine started after cranking about 15 seconds, and settled down to a smooth idle after another 5 seconds. Ran about 15 minutes, reached operating temperature, increased RPM up to 2000 momentarily a few times, all sounds good. Restarts easily.

Unfortunately I will be away until mid October and will not have time for a test drive before leaving, so I will not know until October if changing the injectors solved the original problem I was having.

I do agree that having one of the rebuilt injectors fail is disconcerting, and raises suspicion about the other five. On the other hand, infant mortatity is always an issue with both new and rebuilt parts. But pulling them all out for retesting now could possibly induce another failure that wouldn't have occurred other wise. In this case, looking back to when I initially tried to start the engine it did try to start briefly on the third thirty-second cranking interval. Then it died and never fired again. So at that point it had to have had HUEI oil pressure and everything else working including all six injectors. The failed injector must have failed at that time, so it likely did passed the rebuilders inspection/test before it was shipped. So this adds another concern and that is that another injector failure of this type would not just disable that cylinder, but be a single point of failure that shuts down the engine. Could occur anywhere, anytime, with any new or rebuilt injector, just a function of the engine design.

You suggested having a cylinder cut-out test done to verify cylinder contribution. Would this test at idle be suficent, or would you also suggest doing at power. Doing it at power is a little more complicated.

I also wanted to pass on to you that I was able to locate and install new injector plug packings. Previously I had installed some O-rings in place of missing or leaking packings at your suggestion. I have the early plastic plugs with the plastic tabs that break off. Two of my plugs had broken tabs so were held in place with zip-ties. The plug repair kits are available at www.densoautoac.com (http://www.densoautoac.com), enter the item number Y1C1CATHUEIC7C9 in the search bar. Each plug comes with a new packing. At $1.10 each, they are cheap enough that you can just use the packing and throw the plug away. The packing looks like it should also fit the later style plugs, as well as the IAPCV plug, and perhaps a few others. The site accepts Paypal and my order arrived in less than a week. They ship from China by DHL, so shipping a bit pricy, about $26.00 for the package.

You commented that I'm not a Caterpillar fan in your last post. I just wanted to mention that I didn't start out that way. I only got that way after several disapointing and frustrating interactions with Caterpillar Service Departments.
Title: Re: Cat 3126, low power, low boost, low fuel consumption
Post by: David.e.atherton on August 07, 2019, 06:57:08 AM
gbarney, yes I understand you have lost faith in actions of some service shops and have
gone different direction other than Caterpillar. One thing is missing with all of this the OEM
caterpillar parts are the main player here and there are not involved in your option with
Service of Dealerships, the parts just sit on shelf waiting to be bought by someone with a
Caterpillar engine. Long story short, yes Engine is running and you proved a point you can do with out OEM caterpillar parts and gone open market or aftermarket like kind parts and rebuilding injectors from non- caterpillar shop. Yes failure of injector caused a no start and
big question am I going to gave problems ahead with the other Five injectors. That is your
call, I’m a Caterpillar person and giving direction other than Caterpillar spec’s I do not get
Involved and that failed injector throws up a good example as to why I cannot agree this kind
of repair. Your replacement injector ( Cat Reman ) now Engine runs. Wish you the best ahead.
Ask Dave, Dave Atherton Retired Cat Mechanic
Title: Re: Cat 3126, low power, low boost, low fuel consumption
Post by: gbarney on August 07, 2019, 05:02:50 PM
Hi Dave,
Yes the engine is up and running, thanks to you and your expert guidance and assistance. I cannot thank you enough for the help you have given me on this project and previously as well.

And please don't get me wrong about CAT parts. I always buy the CAT filters, I've replaced a couple of sensors with new CAT parts, and the IAPCV I replaced during this project was a new CAT part. As for these injectors, if I actually knew for certain that I had bad injectors I would likely have replaced them with new CAT units, or possibly CAT rebuilt units. But I didn't know, and neither did the local CAT service shop even after two days on their Dyno. They recommended replacing the injectors "just to see if anything changed," or "just to make sure there isn't a problem with them." New injectors plus labor to install was going to be about $6000.00. To me, that just seemed like a lot of money to spend without any certainty that it would improve anything, or "just to make sure" the injectors aren't the problem. Maybe I'm just cheap.

Having this outside shop rebuild the injectors cost $100 each. So for $600 I found out there was metal shavings in them, and will find out after a test drive if there is any change in engine performance. It is unfortunate that one failed, but it was a known failure mode. If these injectors don't change or improve the low power issue then what ever the probem is, it is something else. If there is an improvement, or even just a change, then there was an injector problem and if I still need to do anything further with injectors I will feel better about spending the money for either new or reman CAT units. And now that you helped me through replacing these injectors, and it turns out it isn't much more complicated that changing a set of spark plugs, I don't have any reason to pay a CAT shop to do it.

Again, I can't thank you enough for all your assistance. I truly appreciate it and could not have done this without it.


Title: Re: Cat 3126, low power, low boost, low fuel consumption
Post by: gbarney on October 05, 2019, 09:58:29 AM
Hi Dave,
I've been away for the past couple of months, I had to leave before I was able to make a test drive on the rig after installing the rebuilt injectors. Now that I am back and was able to do a test drive, I wanted to post a follow up. Pretty simple, engine ran fine, no codes or other issues, but also no improvement in performance. Maximum boost pressure still only 23 psi. Quite disappointing. After the rebuilder reported finding metal particles in the injectors, I had expected better results.

I know you've previously stated that 23 psi maximum boost pressue is normal for this engine, but somehow we are getting different data. The CAT 3126 help line folks have looked up the original test stand data for my serial number, and told me it made 56.4 inches of mercuery boost pressure on the test stand. 56.4 inches of mercury converts to 27.7 psi., and this corresponds with what I recall seeing on the boost pressure gage when I first bought this rig, back when it had much more power for climbing hills.

At this point, I think I've checked or replaced nearly everything on this engine except the turbo-charger itself. Not sure if its is worth trying to replace that or not. The turbine seems to spin freely, and the waste gate moves freely when the actuator rod is disconnected.

Anyway, I wanted to let you know the final result and thank you once again for all your assistance.

Title: Re: Cat 3126, low power, low boost, low fuel consumption
Post by: David.e.atherton on October 05, 2019, 11:57:33 PM
Glen, boost pressure understanding correct information, whoever you feel you want go with
My opinion is clear and stand by information that I posted . Ask a Dave, Dave Atherton
Retired Cat mechanic
Title: Re: Cat 3126, low power, low boost, low fuel consumption
Post by: gbarney on October 10, 2019, 10:07:30 AM
Thanks again Dave for all you assistance. I accept that your information on performance is accurate. I've often found that equipment performance information based on actual field experience is more reliable than a manufacturers "claimed" performance. Your information is also in line with what I was told by the CAT techs when they had the rig on the Dyno, 23psi boost and 250hp measured at the axle is about normal for this engine.

I frequently run this rig through the mountain passes on I-5 in southern Oregan and northern CA. I still have no explanation for why it used to climb those grades in 5th at better than 50mph, and no longer can come close to that. Maybe the turbo waste gate was frozen shut and it was getting over boosted. Maybe prior to my owning it, someone had hacked into the ECM software and modified the operating perameters to increase performance, something that was subsequently overwritten when the ECM was flashed to update the software. My expectation that the prior performance was "normal" seem to have been unrealistic. Unfortunately I've spent way too much time, effort, and money, trying to get better than 37mph in 3rd when climbing these same grades now. It seems that was the best best performance this rig was ever intended to deliver.

In hindsight, I should have traded this rig for something with better performance several years ago when I first realized the perforance had declined. I think I will start that process now rather than wasting any more effort on this one. Seems that nearly any make/model rig I might buy could easily out perform this one - I see them as they pass me, many at a pretty good clip.