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Discussion Starter #1
Hello everyone,


I have a 2008 F250 with the 6.4L diesel. The truck stumbles on takeoff at about 20mph. It will completely cut out and rail pressure will drop. If I stay on the pedal, it will take a few seconds that it kicks back in like normal. I am receiving code P0087 for low rail pressure. 90 percent of time it lacks power. Rail pressure will only hit 19,000psi at WOT. But sometimes it will have full power and hits 25,000psi easily. I have replaced everything on the truck. The tank has been dropped and cleaned, pickup tube has been inspected, HFCM has been changed, both fuel filters, HPFP has been changed 3 times, injectors & jumper tubes, HPFP gasket, HPFP hard lines, HPFP harness (short harness under the heat shield), and the rail pressure sensor. All parts used are known good parts. No contamination has been found in the fuel system. There is no air intrustion. When the problem started, the truck wasn't deleted but it is now. It was deleted when the first HPFP was changed. Occasionally it will throw a P2291 code also.




Thanks in advance for the help!
 

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I see the list of parts replaced which usually eliminates the hard parts - and the common causes of these codes so maybe we can start outside the box this time. I would recommend however putting a fuel gauge on the truck and monitoring the low pressure supply system pressure when the low power symptoms occur. This is a MUST. Pressure should be 3-8 PSI.

After replacing the HPOP did you carry out the fuel volume control valve and fuel pressure control valve adaptive learning parameter reset? This shouldn't cause this concern but it cannot be ruled out.

The diagnostics for this pay a lot of attention to the pressure/volume control solenoids and circuits. Test the solenoids resistance cold and hot - they should measure between 1.5 Ohm - 8 Ohm. I would also recommend load testing the circuits from the PCM to the 4-pin connector near the GPCM.

Verify that the pump has a good VPWR circuit, meaning a solid 12V supply to both green/white wires at the HPFP harness connector - LOAD TEST the circuit and perform a voltage drop test and wiggle the harness while doing so. The VPWR circuit for the HPOP comes from fuse F74 in the battery junction box and it feeds the HPOP, Fan clutch, EGR throttle plate, turbocharger actuator, GPCM, EGR valve and the MAF sensor - any of which could in theory pull the circuit down. Do not forget to remove fuse F74 and look at it closely for fretting (burnt marks) that would indicate poor terminal fitment. I HAVE seen that fuse loose in the fuse block and it drove me nuts to say the least.

Good luck!
 

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Discussion Starter #3
Thanks for the reply!

I have checked the low pressure fuel and it hovers right around 5-6 psi. The adapter learning parameter reset has not been done yet. Is this something that you can do yourself or will it need to be done at a dealer? I also forgot to mention that the entire engine wiring harness has been replaced and it has the same symptoms. The harness came from my other 6.4 that cracked a piston a few weeks ago so I know the harness is good. The last HPFP also came from the same truck so I know that it' s good. I also checked and replaced fuse f74. It didn't have any fretting and it fit tight. I took the truck out for a test drive after changing the engine harness and fuse and it still has the same symptoms. I have Autoenginuity hooked up and noticed every time the code is throw, it is at 19mph for some reason. The only parts in the fuel system that have not been replaced is the fuel lines to and from the tank and the fuel lines from the secondary filter to the HPFP, the line from the HPFP back to the filter, and the return line off the heads back to the filter. Anything else to check? This truck has me very confused.

Thanks,
Chris
Tri State Surplus LLC
 

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Anyone have any more recommendations? I had the VCV and PCV adaptive learning parameter reset done at the Ford dealer yesterday and still have the same issue. Could it be the PCM?
 

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Yes, the PCM could very well be at fault. If you were following the WSM diagnostics there are several pinpoint tests or paths that lead you to replace the PCM. There are likely a few diagnostic steps that have not been performed at this point but since you have pretty much replaced or swapped out everything it's pointing that way. The replacement of any module is usually the last thing to be suspect in any diagnostic routine once everything else has been eliminated. You said that there was no air intrusion - are you absolutely sure?
 

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Discussion Starter #6
I tried to bleed the air through the Schrader valve on the fuel cooler several times and there is no air. Is there a better way to check for air intrusion? One thing that I am a little concerned about is the soft return line coming from the heads and HPFP that comes into the fuel cooler. It has a little fraying. However, both my other 6.4's are the same way. If it was bad wouldn't it pull air that would be visible when bleeding through the Schrader valve?

Thanks again!
 

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I would stop doing anymore self diag and get the high pressure fuel system strategy reset at a Ford dealer. No aftermarket scan tool will accomplish this task. "Clearing Codes" does not reset the strategy.
 

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Going through my notes, the only one of these I have encountered (P0087) had a bad fuel pump with metal debris throughout the system. I replaced the system with the service kit which corrected the concern.
 

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Hello everyone,


I have a 2008 F250 with the 6.4L diesel. The truck stumbles on takeoff at about 20mph. It will completely cut out and rail pressure will drop. If I stay on the pedal, it will take a few seconds that it kicks back in like normal. I am receiving code P0087 for low rail pressure. 90 percent of time it lacks power. Rail pressure will only hit 19,000psi at WOT. But sometimes it will have full power and hits 25,000psi easily. I have replaced everything on the truck. The tank has been dropped and cleaned, pickup tube has been inspected, HFCM has been changed, both fuel filters, HPFP has been changed 3 times, injectors & jumper tubes, HPFP gasket, HPFP hard lines, HPFP harness (short harness under the heat shield), and the rail pressure sensor. All parts used are known good parts. No contamination has been found in the fuel system. There is no air intrustion. When the problem started, the truck wasn't deleted but it is now. It was deleted when the first HPFP was changed. Occasionally it will throw a P2291 code also.




Thanks in advance for the help!
i no its been 2 years but im having the exact same problem did ever fix the problem let me no thanks
 
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