2006lly--p0087

[jimboagogo]

I have done some research on this DTC and it appears usually the cause orriginates on the supply side of the fuel system.I have a max of 5" on the supply side,no air in the fuel.I have done a return flow test on the injectors and all is Ok there.The data stream shows that the balance rates on the injectors is in acceptable range.I tried a regulator,a rail pressure sensor,when you try to test the regulator it doesn't want to go anywhere other than 30%.It will start fine cold but after it get's to opperating temp it won't restart,the rail press.won't build.I don't like to just change parts because they aren't cheap and very labour intensive.I couldn't find much info on checking the high press.pump.The desired and actual fuel pressure are not really close untill you rev it up.When you drive it they are way appart when you drive it hard.I think it's the pump but I would like to be ceterain.

[jimboagogo]

Well since no one has any ideas,maybe someone can tell me how much warranty they have on the fuel system.This truck is only 3yrs old with 124,000 miles.If it's got some warranty left I'll ship it off to the dealer and stop pulling my hair out(can't afford to loose any more).Thanks in advance Jim

[joed]

As for warranty, I think you were finished at 100k - I believe the diesel engine warranty is 5 yrs or 100k miles, whichever comes first.

Sounds like you may have already checked most of this, but here's the diagnostic procedure from my service manual subscription (one thing it mentions is the fuel heater may always be on, thinning the fuel too much):

CONDITIONS FOR SETTING THE DTC

P0087

* The actual FRP is more than 15 MPa (2,176 psi) below the desired FRP.OR
* The actual FRP is less than 22.5 MPa (3,263 psi) .

DIAGNOSTIC AIDS

P0087

* When ambient temperatures are below 0°C (32°F) , the fuel tank pickup screen may be iced over from water in the fuel tank.
* When power enhancing devices have been attached to the fuel rail pressure sensor circuits, this DTC may set and adversely effect the fuel system components.
* When the fuel heater is on all the time, the fuel temperature may stay high enough to thin the fuel and cause this DTC to set.

CIRCUIT/SYSTEM TESTING

IMPORTANT: Fuel pressure control will be disabled if DTC P0087, P0088, P0912, or P0193 are set. Codes must be cleared to enable the device control.

P0087

1. If DTC P0090, P0168 or P0191 is also set, refer to Diagnostic Trouble Code (DTC) List - Vehicle. See: Diagnostic Trouble Code Descriptions
2. Attempt to start the engine. IMPORTANT: Ensure that the transmission is in Park or Neutral with the parking brake set.

o If the engine does not start, refer to Engine Cranks but Does Not Run. See: Symptom Related Diagnostic Procedures\Engine Cranks But Does Not Run

3. Install the J 44638 to the fuel rail service port and slowly increase the engine speed until reaching wide open throttle (WOT).

o If more than 5 inches of vacuum was present during engine speed increase, replace the fuel filter and inspect for fuel system restrictions.

4. Command the fuel pressure control to 180 MPa (23,206 psi) with a scan tool. Observe the Actual Fuel Rail Pressure parameter. The actual fuel pressure should be the same as the commanded pressure.

o If the Actual Fuel Rail Pressure is less than 145 MPa (21,030 psi) , refer to Fuel System Diagnosis - High Pressure Side. See: Component Tests and General Diagnostics\Fuel System Diagnosis - High Pressure Side

5. Operate the vehicle within the conditions for which the customer complaint occurs while observing the J 44638. You may also operate the vehicle within the conditions that you observed in the Freeze Frame/Failure Records. IMPORTANT: If the fuel temperature is near 121°C (250°F) during the duplication of the complaint, or in the Failure Records for this DTC, inspect for a restriction in the fuel cooler air flow or the fuel heater always ON. Refer to Fuel Heater Always On. See: Component Tests and General Diagnostics\Fuel Heater Always On

o If the vacuum was more than 12 inches Hg of vacuum at any time in the operating range, inspect for a restriction in the fuel supply lines.
o If the vacuum was always less than 12 inches Hg of vacuum, refer to Diagnostic Aids.

Hope this helps.

[jimboagogo]

Thank you very much for the information.When I did the return flow test I did it right at the injectors.Yesterday I cheched the return flow at the disconnect at the left valve cover.It has alot of return fuel.I checked the relief valve and it seems good.Can anyone tell me how much fuel the pump should return.I'm wondering if the cascade valve is stuck or broken spring?

[GMC Tech]

Ramp this up again when it's first started - drive it till it gets warm and ramp it up again.
Let it stay ramped for a minute and see if it slowly looses pressure.
If it slowly looses pressure - you probably have a bad pump.
If the pressure pops down quickly - you have a bad fuel rail pressure relief valve most likely.

One thing I do when I suspect a FRP of going south is to remove the return line from the FRP and install my own return line from the FRP into a clear container and go out and drive the truck. If it losses power, I check the container...any fuel in the container, It gets a FRP.
If I were you - knowing that the FRPR is easy to replace now - just take it out of the rail -
and that when it leaks - it doesn't really squirt like you think it would when it's bad...
put a new one in it and road test it again.

If that doesn't work - take the fuel line off the front of the left rail and see if it has some
shinny metel - like valve grinding compound in the inlet area. If it does - the inj. pump is
coming apart and plugging the rail. Sometimes this can be taken like wear in stuff and you
can get away with drilling out the rail or just taking a welding tip cleaner to it.

If it needs a pump - don't forget - theres another fitting that's the same inlet size on the right rail
that needs to be probed when you do the pump.

[Kennedy]

I have done some research on this DTC and it appears usually the cause orriginates on the supply side of the fuel system.I have a max of 5" on the supply side,no air in the fuel.I have done a return flow test on the injectors and all is Ok there.The data stream shows that the balance rates on the injectors is in acceptable range.I tried a regulator,a rail pressure sensor,when you try to test the regulator it doesn't want to go anywhere other than 30%.It will start fine cold but after it get's to opperating temp it won't restart,the rail press.won't build.I don't like to just change parts because they aren't cheap and very labour intensive.I couldn't find much info on checking the high press.pump.The desired and actual fuel pressure are not really close untill you rev it up.When you drive it they are way appart when you drive it hard.I think it's the pump but I would like to be ceterain.

What RPM was this 5"hg measured?

[jimboagogo]

5" wot under load.I learned yesterday that the fella that works for me punched the engine code in the scanner wrong,so its an LBZ not LLY.I had a buddy come over with a Tech2 and it can't ramp up the regulator either(was worried it was my scanner).I checked with the graphing meter when he was trying to ramp it up and the signal is good so I'm in the midst of changing the HP pump.Boy who ever was the engineer that designed that engine certainly wasn't planning on working on it.When I get it back together I'll report. Thanks for the info/advice every one......... Jim

[jimboagogo]

Well I finally got it finished.New pump seems to be the ticket.I didn't have a chance to test drive it yet,but the regulator now works and the actual and desired are bang on.I think they wouldn't be as ignorant to change after youve done 1 or 2 .Anyway I'd like to say thank's to everyone here at this site for trying to help out......Jim

[Donny D]

Im doing a pump,injectors,hard lines and both rails on a 2013 gmc at work now....that engineer is very lucky he was nowhere near me today,and tommorow for that matter! did they really have to design it so you have to strip the front of the engine right to the block...