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Old 06-02-2019, 06:30 AM   #1
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HEUI pump intermittent operation

We have a 2003 Journey with a Cat 3126E. I'm getting a check engine light (code 39) and the engine goes into limp mode, a few seconds to a few minutes later the light goes out and the engine returns to normal power. This has gone on for 460 miles sometime going 90 minutes between problems and some time it happens every couple of minutes.
Does this sound like the HEUI pump to anyone? I can't imagine the pump working on and off.
thanks,
Dick
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Old 06-02-2019, 08:35 AM   #2
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In this IRV2 Forum, they have a lot of uploaded diagrams and one may be what you need to fix your issue. GO into IRV2 DOWNLOADS and then look for MANUALS and I hope you find the one you need.
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Old 06-02-2019, 09:12 AM   #3
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Is it hard staring at any time? Have you experienced a "stumble" after starting then seems to idle okay? Need to have a bit more info to aid in diagnosing.
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Old 06-02-2019, 09:13 AM   #4
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Quote:
Originally Posted by BradlyHart View Post
In this IRV2 Forum, they have a lot of uploaded diagrams and one may be what you need to fix your issue. GO into IRV2 DOWNLOADS and then look for MANUALS and I hope you find the one you need.


What exactly would you be looking for. We are also having some issues that could be the Heui pump, that sound very much like yours.
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Old 06-02-2019, 09:20 AM   #5
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Quote:
Originally Posted by dickb46 View Post
We have a 2003 Journey with a Cat 3126E. I'm getting a check engine light (code 39) and the engine goes into limp mode, a few seconds to a few minutes later the light goes out and the engine returns to normal power. This has gone on for 460 miles sometime going 90 minutes between problems and some time it happens every couple of minutes.

Does this sound like the HEUI pump to anyone? I can't imagine the pump working on and off.

thanks,

Dick


We had an on again off again problem with the engine going into limp mode and check engine light coming on. Left us stranded in the middle lane of a busy Seattle freeway one tome. It has always eventually temporarily cured itself and allowed us to drive to safety and repairs. Changing Heui pump seemed to fix it $$$$ about 4 years against. But symptoms have now reoccurred! Have been diligent about fresh clean oil. Diesel maybe a little less so as it has to sit for several months at a time with our lifestyle. Would really like not to be stuck on freeway again. Was a very scary experience.
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Old 06-02-2019, 09:25 AM   #6
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code 39 is or could be several components. Defective HEUI (coil/connection), Defective IAP sensor or a major oil leak on an injectors that is causing intermittent oil pressure.

I have experienced all on several coach's. Best way to analyze is by testing the Oil Rail pressure. Should be around 800/850 psi at idle and varies up to 4,200 relative to engine load. Additional ports are available of the head to insert fittings and test the pressure.

If it starts up within 3-4 seconds, idles fine (no stumble) then it is either:
HEUI: internal coil or connection (faulty wiring).
Or
Injector with a leak.

Check wiring first. cheapest possible resolve. Chipmunks/mice are notorious for chewing on wiring.....
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Old 06-02-2019, 09:34 AM   #7
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You can complete a self inspection of the HEUI for signs of internal failure mode. New style HEUI with the rectangular head is pretty simple. PM me and I can send you a detailed procedure to complete. Takes longer to clean the outside so dirt and debris doesn't contaminate the inside then the inspection itself.

The axial piston group does not "come and go". When they fail, it's all over but the hook. This is on the control side (coil/wiring) or IAP sensor ($160.00)
Good luck
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Old 06-02-2019, 09:35 AM   #8
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Why would it be intermittent?
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Old 06-02-2019, 09:43 AM   #9
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The IAP sensor is a pressure transducer and feeds back to the ECM the current pressure.
I have experienced several original IAP's that produced and intermittent feedback to the ECM and then throwing a code. Now, that's not to say it cannot be other components, only that HEUI pump pressure/volume doesn't "come and go" unless told to do so by either the ECM not receiving accurate data or the output of the ECM not driving the HEUI to the required pressure. Like a computer: "Garbage in, garbage out".
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Old 06-02-2019, 09:58 AM   #10
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Another IAP sensor test that so often appears.
If the last time you ran the coach it was perfect then one day you attempt to start and it bucks and stumbles. A simple test to prove the IAP failed is to unplug the connector. If you restart the engine and it idles just fine then the IAP has failed. It is located in the head, front left side with a 3 pin connector:3126/C7. I have seen this often.

BUT, I have experienced an owner with a defective IAP, that attempted to use starting fluid to try to start and blew up the filter housing. NEVER use starting fluid for the air inlet heating grid will ignite the starting fluid.
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Old 06-02-2019, 09:58 AM   #11
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Following your thread to track the solution ; hope it's just the sensor .
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Old 06-02-2019, 04:36 PM   #12
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Thank you all for your insight and replies. We traveled 245 miles today and didn't get pulled over once for blocking traffic (limping between 30-45 mph).
Today wasn't on and off--all off! Yikes, what a day.
We are currently in a campground 5 miles from a Peterbilt service facility that is advertised by Cat as an authorized service dealer.
I'll surely let the forum know the outcome as we are still 3000 miles from home.
The big reason for making the original post was to reinforce my thinking about it not being the pump.
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Old 06-02-2019, 09:41 PM   #13
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The pump when failing generates metal. That metal gets into the injector solenoids causing the solenoid to stick "open" this dumps the HEUI pressure in the rail. This can and does cause a low heui pressure warning. If the metal gets washed out by the normal firing then the pressure comes back up and the warning/diagnostic code will go inactive. While this is occurring- metal in the injector solenoid- you can get misfiring, knocking, low power, no acceleration and hard start or no start. This is how the symptoms can come and go. Safe Travels
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Old 06-03-2019, 05:38 AM   #14
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Excellent point Cat, thanks. I'm headed of to Peterbilt in 15 minutes (in the car)

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