Author Topic: Cat 3126, low power, low boost, low fuel consumption  (Read 3928 times)

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Offline gbarney

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Cat 3126, low power, low boost, low fuel consumption
« 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.

Glenn






Offline David.e.atherton

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Re: Cat 3126, low power, low boost, low fuel consumption
« Reply #1 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

Offline gbarney

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Re: Cat 3126, low power, low boost, low fuel consumption
« Reply #2 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.

Glenn

Offline David.e.atherton

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Re: Cat 3126, low power, low boost, low fuel consumption
« Reply #3 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

Offline gbarney

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Re: Cat 3126, low power, low boost, low fuel consumption
« Reply #4 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.


Offline David.e.atherton

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Re: Cat 3126, low power, low boost, low fuel consumption
« Reply #5 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

Offline gbarney

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Re: Cat 3126, low power, low boost, low fuel consumption
« Reply #6 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.

Glenn

Offline David.e.atherton

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Re: Cat 3126, low power, low boost, low fuel consumption
« Reply #7 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

Offline Journey

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Re: Cat 3126, low power, low boost, low fuel consumption
« Reply #8 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?
2004 Journey 36G Cat C-7
1995 Jeep Wrangler

Offline David.e.atherton

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Re: Cat 3126, low power, low boost, low fuel consumption
« Reply #9 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

Offline gbarney

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Re: Cat 3126, low power, low boost, low fuel consumption
« Reply #10 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.

Glenn

Offline gbarney

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Re: Cat 3126, low power, low boost, low fuel consumption
« Reply #11 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?

Offline David.e.atherton

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Re: Cat 3126, low power, low boost, low fuel consumption
« Reply #12 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

Offline gbarney

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Re: Cat 3126, low power, low boost, low fuel consumption
« Reply #13 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.

 

Offline ziggyh

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Re: Cat 3126, low power, low boost, low fuel consumption
« Reply #14 on: April 18, 2019, 06:09:40 PM »
Gbarney, have you checked to see if you have any exhaust restriction beside the prac break.
ZiggyH

2007 Revolution LE
C9

Offline gbarney

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Re: Cat 3126, low power, low boost, low fuel consumption
« Reply #15 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.

Glenn

Offline ziggyh

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Re: Cat 3126, low power, low boost, low fuel consumption
« Reply #16 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.
ZiggyH

2007 Revolution LE
C9

Offline gbarney

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Re: Cat 3126, low power, low boost, low fuel consumption
« Reply #17 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."

Offline ziggyh

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Re: Cat 3126, low power, low boost, low fuel consumption
« Reply #18 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. 
ZiggyH

2007 Revolution LE
C9

Offline gbarney

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Re: Cat 3126, low power, low boost, low fuel consumption
« Reply #19 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.

Offline ziggyh

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Re: Cat 3126, low power, low boost, low fuel consumption
« Reply #20 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
« Last Edit: July 03, 2019, 07:40:03 AM by ziggyh »
ZiggyH

2007 Revolution LE
C9

Offline gbarney

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Re: Cat 3126, low power, low boost, low fuel consumption
« Reply #21 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.

Offline ziggyh

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Re: Cat 3126, low power, low boost, low fuel consumption
« Reply #22 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.
ZiggyH

2007 Revolution LE
C9

Offline gbarney

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Re: Cat 3126, low power, low boost, low fuel consumption
« Reply #23 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.

Offline ziggyh

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Re: Cat 3126, low power, low boost, low fuel consumption
« Reply #24 on: July 08, 2019, 07:11:21 PM »
Thanks, would like to know the out come, good luck.
ZiggyH

2007 Revolution LE
C9