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Discussion Starter #1
So I am working here on my future motorhome project - 2011 Express 4500 shuttle bus, 156k miles. It was used by Enterprise rent-a-car in Miami airport.



I bought it as is with "crank no start" and later discovered the famous CP4 failure. Replaced the CP4, fuel rails, fuel filters, put brand new injectors in it - and now it seems to be in the ENGINE POWER REDUCED mode all the time, and I get codes, including the P2463.
I have a Tech 2.


I started doing service regenerations, the truck has been high revving pretty much all day, burned approx. 7 gallons of diesel and all I achieved is the soot level went from 89g to 81g.



I am not sure if regenerations really work on this truck, as the Tech 2 shows "DPF Regeneration Status - Inactive" when commanded on, but "Post-Injection" does change to "Active".
There has been a calibration update from GM for 2011 LGH to address Service Regen issues but it seems that my ECM is already updated:

Please note that 2011-2012 LGH do not use the HCI (9th injector) for Service Regeneration.

The Max EGTs I observed were these:

It does not go towards 800°C like the bulletins suggest.

Current very weird issues:
1) ECM conflict of interests! I'm doing this in SoCal, so it is warm outside. Coolant temp needs to be above 70°C for the Regen to work, but during the Regen, the ECM activates the EV fan clutch for some reason, and my temps quickly go down from 92°C to 67°C at which point the Tech 2 displays this and quits:

I tried unplugging the fan clutch, it helps to keep the temps up but it registers 3 fan clutch codes and then regen doesn't work.
I even had to remove the clutch, unbolt the fan blade and connect it back together, to help keep the codes out and temp up. But I had to put a regular household fan in front of the radiator to cool it down, cause it overheats otherwise. I do not understand why I have to do this.

2) Actual/Desired Fuel pressure control follows me up to 85 MPa at idle but won't go higher. Injectors are brand new from eBay ID desmoparts (ebay item ID 381457973661)

3) Most of the time it's just P2463 - "DPF Soot accumulation", but sometimes it throws me a bunch of counter-intuitive codes, such as P128E, P0087 (Fuel Pressure Low) and P0088 (Fuel Pressure High) simultaneously:













Is my fuel system working properly? Is the CP4 pressure being limited due to P2463?
Should I spend a few more days trying to do service regenerations? Should I replace the whole DPF at $2000+? Is my problem somewhere else?
 

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Discussion Starter #3
I honestly don't think it would have worked had I not applied a tune to it first.
Very interesting. I only have Tech 2 so far. What does a tune do to a service regen process so it could finally work? As far as I understand it, my soot does not burn because of not high enough EGT temps, and why they do not go high I do not know.
 

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Discussion Starter #5
So I left the truck sitting for 3 days, and at the time the Soot Level was at 81g. Today I came to perform the Service Regen again but it shows me this:
.

I figured I would do a regen anyways, it runs stable at 2000RPM but EGT won't go over
.
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Currently the only problem is that Fuel Rail Pressure won't go too high at idle, sometimes I get P0087. New pump, New rails, New 8 injectors.


What could be the culprit? Please help.
 

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Hard to say what is up with the fuel system. Did you replace the secondary regulator?


It will not do a proper regen until you get past the DTC's. I can't say for sure if all DTC's lock it out or not, but it's beginning to appear that way.
 

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Discussion Starter #7
Yes I did, although I'm not sure if there is a specific tightening procedure, as it has a lock nut. I tightened it, and I don't see any fuel spray around it.

Current codes P0087 and P128E. When trying to accelerate, as fuel demand increases, engine bogs down badly:

It goes up a very steep hill at 2mph. Can make it go 30mph on a flat road.

Sent from my VS985 4G using Tapatalk
 

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Do you have a lift pump and/or have you measured fuel supply side restriction?
 

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Discussion Starter #10
okay, so I purchased the Kennedy gauge and here it is.
Ignition ON, engine OFF, prime pump running:



Engine ON:


So it seems the supply side is okay. Injectors are brand new, what else could be the issue? Truck bogs down when attempting to drive, and throws P0087, P128E and sometimes P0088. FPRV? FPR1?
 

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Did you flush the metal filings out of all the fuel lines when you did the repair?

You replaced the fuel pressure regulator #2/pressure relief valve (in end of left fuel rail) again? A new rail comes with one installed. If they are not torqued properly they can leak internally.

Test current flow through FPR2 with engine running, forget exact values, but should be under 1A, I think around .5A.

If you didn't get all the metal out (return lines, high pressure lines & chassis lines) you could have ruined more parts.
 

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Discussion Starter #13
oh sorry that's the FPR1 reading, will check on the FPR2 soon.

No I haven't flushed the lines and I did not drop the tank. I saw that GM bulletin that called for a $10k job to replace the whole fuel system with parts listed on 2 pages, but this bus is not under warranty, and I'm working in a backyard... I hope I haven't ruined the other parts, and from what I'm reading on this forum, people only replace the CP4, rails and injectors and are fine afterwards.

After I only replaced the CP4 but before I replaced the injectors, desired pressure won't go above 40MPa. After the injectors got replaced it now goes to 90MPa.
 

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Discussion Starter #14
rob1, from your experience can you elaborate on the CP4 pump - is it always a boolean "working perfectly" or "grenaded"? The one I installed was used from eBay and seller claimed 30k miles on it, it looked very clean though. Can a pump be half way bad that the engine would run but not go over certain pressure?
 

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A pump can be bad without having "grenaded"

I have had bad pumps range from no start to just CEL

One of the first tests when doing high pressure fuel diagnosis is ramp up commanded fuel pressure and see if it matches actual. I will check later as to what else is checked to condemn a pump. I will also check for you if one of your codes should have priority over another.
 
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