Author Topic: Caterpillar 3126 Sputters and dies on freeway, help think its fuel related HEUI  (Read 1176 times)

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Offline dhanson12435

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Hello all, ran into some trouble I'm hoping someone with good experience on a 3126 Cat engine could help. I was running my 2000 Endeavor with a 330 Cat 3126, 130K miles down the freeway and it began to sputter and eventually died and will not restart.
Oil, temp and all my gauges were all in the normal areas when this occurred. I think it is fuel related.

Here is where I'm at. The codes tell me, 15- Injection pressure sensor fault, 39- Injection actuation pressure system fault, and error codes 72,73,74 (all cylinders fault). Some say its a computer but I think it ran out of fuel.. My oil pressure still climbs when cranking and gauges register still. 

I need help understanding the fuel system. I checked fuel filters (replaced 3K miles ago), look clean and full, no water. I removed the rear of the head return line and regulator and turned over engine and no fuel comes out.. It does come out when I hand prime it.. This makes me think the transfer pump on the HEUI is not working. I have no way to check high pressure oil numbers as I do not have the proper diagnostic equipment. So does this mean my HEUI pump likely failed? Is there something else stopping fuel flow?

Offline David.e.atherton

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dhansen, hi lets troubleshoot the injection actuation pressure sensor first and this sensor is located right
behind the fuel transfer pump. The sensor has a mushroom head along with a pig tail coming off the sensor
about 12 inches long with a triangle electrical end that plugs into the electrical harness. Locate the IAP sensor
and disconnect the triangle connector than start engine. If the engine starts up and idles with sensor disconnected that tells us the sensor is bad. Note : engine will idle but will have any power to pull itself.
Ask Dave, Dave Atherton Retired Cat Mechanic

Offline dhanson12435

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Well with no fuel flow I did not think the sensor would help but I tried as you mentioned with no success. I got adept ape to confirm that if no fuel flow is present from the HEUI but it does flow when you hand prime through the head return line the transfer pump is the issue. It is likely that the gear on the assembly may have backed off and is now not making contact of the from flywheel. I wont be able to confirm this until I figure out how in the world I'm going to get this pump off in the cramped area its in.

Offline David.e.atherton

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dhanson, in troubleshooting problems my approach is check simple things and in most cases problem is
found. Reading your post I really do not recommend going after the fuel transfer pump replacement it is
possible your advice may be correct but unless trained remove and install Fuel transfer from Heui pump.
Would suggest problem areas, air entry into fuel system from fuel tank to fuel transfer pump under suction
from fuel transfer pump . Fuel return pressure regulator screen plugged or plugged orfice in check
Valve. In closing removal of Heui pump from engine is a must before fuel transfer pump this is the easy
part. Fuel transfer pump is where problems start, transfer pump is attached via 4 long bolts that go through
Heui pump housing and can get access Heui pump drive gear must be removed. This next step removing
the 4 long bolts holding  transfer pump Has springs and parts inside Heui pump that will fly all over the bench
when last bolt removed . Than at that point put all the parts in. Box and take it to caterpillar and have Heui
Pump and fuel pump put back together. You can buy a Reman Heui pump with fuel transfer attached as unit
with your present Heui pump cost $ 2,750. Ask Dave, Dave Atherton Retired Cat Mechanic

Offline dhanson12435

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Hi David, thanks for all the info.. Wish I could scan the computer to see whats going on with all the sensors but do not have the equipment.  Let me provide some more info on my setup. My 3126B engine uses an older style pump. The transfer pump only has two bolts holding it on. I have actually already replaced the whole HEUI (10r-7053) pump it and still see no improvement in fuel flow. Perhaps the fuel flow is normal and I'm not suppose to see a lot fuel flow. I know that fuel flows like no tomorrow when hand pumping it. I did pull the regulator in the back of the head. It looked clean and would allow some flow through it when hand pumping it. I even tried replacing the injection actuation pressure sensor with no success. The motor starts with starting fluid but that is the only way it runs. With all my fun I forgot to put the oring on my HEUI pump for the area around that seats on the engine so I will have to pull it back out later if oil leaks out..Has nothing to do with running but another day of torture if it will leak out of there..

Offline David.e.atherton

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dhanson, first your problem is not a diesel fuel problem but is a engine oil problem. My first suggestion getting advice off U tube is just a opinion and not endorsed via caterpillar..if we want to address the problem with
technical information that can be backed up with factual information. Second question are you preforming
the work on engine or service shop. Unless we have basic understanding of how much damage that can
happen ( use of starting fluid is not recommended ) can destroy your engine. Replace or rebuild $ 30,000
Plus dollars. Ok engine will run only on starting fluid, this is telling you the injectors  will not fire but diesel fuel
is returning to tank ( clear line at return fuel pressure regulator ) on back of engine head With engine turning
over. The reason injectors not working first no power to injectors from ECM and second if injectors do have
power from ECM than there is no high pressure engine oil going to injectors. Heui pump cannot produce
870 psi cranking pressure to operate injectors, injection actuation pressure regulator  event code 42-11,
Injection pressure sensor, last could be a bad injector event code 164-4 or 163-7. This is where your problem
Is located. In closing starting fluid will settle in bottom of the charged air cooler while cranking and running
on starting fluid, if at any time engine would start on diesel fuel you are in a engine runway mode and can
destroy your engine within 30 seconds or less and you cannot shut engine down.  Ask Dave, Dave Atherton
Retired Cat Mechanic

Offline dhanson12435

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Yes I'm doing the work myself. I have a lot of experience repairing autos but first time on a diesel.  I see nothing but stories of people paying the pros to replace parts that do not fix anything. I can do that myself for a lot less. I did not want to crank it on starting fluid but several folks told me that was the only way to get enough rpm to feed the oil pressure needed. Just need to have a computer hooked up to see what is going on.  Have called on a couple of pros to come out.. One has already made excuses on why they did not show up today and the other cant be here for a few days. Its frustrating..

Offline David.e.atherton

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Dhanson1235,  I have to disagree with your thoughts and with out formal schooling on this engine going to be very hard to relate what to do correctly. On my post I pointed out area of your problem and also gave you the
event codes of problem components removing the need to connect Cat ET diagnostic service tool. I mentioned
Cranking engine over to start , the engine go oil pressure has to have 870 psi to start and running hp pressure
will read  3,500 to 4,100 psi . Diesel fuel pressure 58 psi idle and  74 to 80 psi. First things first, is the Heui
Pump putting it correct. Oil pressure to start.  Than check the IAPR do you have power to operate this regulator
from the ECM. If there is no power to ECM than you have a electrical problem.than the IAP sensor. Again
These area of concern that will correct your problem. Ask Dave, Dave Atherton Retired Car Mechanic

Offline dhanson12435

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Thanks Dave for all the feedback.. I'm trying to learn. Here is where I'm at after today's battle.

I was able to get a Snap on Scanner to look at the engine in more detail.

The engines standard oil pressure was 30-40 psi after the starter running 10 seconds.
The High pressure sensor read between 1100 and 1500 psi during cranking..
It has fuel at the head.. I have no way to check that pressure, seems weak and that it is why I been running down this path. I tried to adapt a fuel pressure gauge to the filter manifold but could not locate the odd thread size needed..Without a gauge who knows.. I would love to see what is doing when I can get a gauge.. Maybe that is when I would see a higher pressure like you mentioned?

So now that I have a scanner to look at, I can clear codes, crank it and see whats going on.. Random injectors give faults...With no where else to go I pulled an ECM from a friends CAT 3126 and tried it on mine motor... Bingo.. It started right away.. Did not run good at all. I assume wrong coding and what not. Also needs to clear some air out of head? I did want to run long like that.. I did crank it again, just to see.. It started... Anyway I think I need an ECM...

Offline David.e.atherton

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dhanson, looking back at my two post you will notice troubleshooting your problem in no start with aid of starting fluid. Reading back in both post I did indicate listing power to Injection Actuation Pressure Regulator
from engine ECM cause no start and without power high pressure engine oil cannot operate the injectors
because it requires power from engine ECM. Yes very good you have located your problem by switching the ECM. You will need new ECM replacement set up by caterpillar to your engine serial number and injector
codes. My suggestion take your present ECM to caterpillar where they can remove all data and program
New ECM for you. Do not go with used like kind ECM or aftermarket reprogram ECM. Last note the little short
ground strap a must when reinstalled the new ECM.  Ask Dave, Dave Atherton Retired Cat Mechanic

Offline dhanson12435

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Ok so going with the ECM being the likely culprit i took my original ECM to a shop that specializes in repairing and refurbishing ECMs. I could not spend $3k plus programming and service fees at a CAT shop.  Anyway. They tested my original and said it had nothing wrong with it, cycled everything it should. Well I told them that it wont start with it but would with another ECM. They insisted it was good and to save my money but I told them sell me another I will have a spare.. I do not want to be stranded on the side of the road again. Went and installed the original, still no start.. Installed new "refurb" starts, runs good.  SO watch out for "good" ECMS...So in the process of all my hassle at least I learned a lot about my 3126, have spare parts and can at least now how to and not to do things.. I sure wish I would have known that very little flow is expected from a transfer pump on that HEUI.. I wouldn't of been so stubborn in chasing a diesel flow issue.... sure do not see any where close to 40 psi during cranking, its maybe 3 psi...

Offline David.e.atherton

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dhanson, yes life is a learning experience as I indicated my view about direction on your ECM ( you got lucky )
Yes there aftermarket repair shops in the long run will not save you money as they indicated with your old ECM
there was nothing wrong with it. The part about  providing technical information for people needing assistance,
it is the expert experience that always want to express there thoughts that caterpillar parts to expensive. Let
me  be very clear this is why caterpillar does not waste there time helpIng people with technical advice and look
around there are getting less Caterpillar  service shops working on motorhome. I’m not a fan for buying
Aftermarket caterpillar parts but have spent countless hours troubleshooting aftermarket  like kind engine
parts that are removed and replaced with a OEM Caterpillar parts. Ask Dave,Dace Atherton Retired Cat
Mechanic

Offline dhanson12435

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I agree that OEM is the way to go, a repaired OEM ECM is a risk for sure. I will have to hope I can get some use out of it before trouble hits again.. So on another issue that showed up, my CAT reman HEUI pump give me problems a day after I thought all my issues were resolved. It led me down a path of more troubleshooting. I finally figured it out, the Solenoid valve on it was defective.. I put my twenty year old one back on and my engine is back up and running... Perhaps CAT changed China vendors with the new one, IDK..