6.6L duramax low fuel rail pressure

[Master Ase Diesel Tech]

I have a 2006 c5500 with the 6.6l duramax that has a p0087 dtc. in the beginning it was running rough and after checking it with the tech II found that the actual fuel pressure was not anywhere close to the demanded fuel rail pressure. I removed and replaced the high pressure fuel pump and the engine purrs like a new one now. the problem I have now is that when you accelerate over 2,000 rpm the truck goes into limp mode. if you stay under 2,000 the truck runs fine. the truck is not smoking like it was when it first came in. I have replaced the frpv and checked the lines to make sure that they are not collapsing under load. when the engine pedal is pushed to the floor the demanded fuel pressure is 20k to 23k psi but the actual psi never gets over 11k. does anyone have any other suggestions?

[More Power]

Welcome to The Diesel Page.

A good source of information for the P0087 trouble code can be found in the following forum thread:
http://www.thedieselpageforums.com/tdpforum/showthread.php?t=35292

Jim

[Kennedy]

Start with a bottle test to verify the relief valve condition. If it never gets over 11k it likely is dumping.

In my experience it is almost never the CP3 pump and almost always injectors (assuming the relief is good.

[Master Ase Diesel Tech]

Welcome to The Diesel Page.

A good source of information for the P0087 trouble code can be found in the following forum thread:
http://www.thedieselpageforums.com/tdpforum/showthread.php?t=35292

Jim



thanks jim, I have already tried all of that and still the problem exists.

[Master Ase Diesel Tech]

Start with a bottle test to verify the relief valve condition. If it never gets over 11k it likely is dumping.

In my experience it is almost never the CP3 pump and almost always injectors (assuming the relief is good.


if the injectors were bad, wouldn't it be smoking or skipping? the local dealers diesel technician that we deal with on a daily basis is saying that he thinks that it is the fuel rail pressure sensor. he says he has had to replace a lot of them on the 6.6l that comes in the c5500 Kodiak.

[Kennedy]

I've been through this so many times in recent years that I started to deflect callers to my Tech Tips. I hate to do this as Tech/Troubleshooting is at the core of my business, but I just end up spending too much time on the phone and with the injectors being the most expensive piece of the puzzle...

If you have the fundamentals verified, he root cause 99% of the time is injector(s) with high return rates.

We've had some success depending on how bad they are with adding lift pump and also ECM tuning to help command up the additional flow needed to keep up.

I ask about a bottle test because I recently had a customer that assumed his "race plug" meant that he did not need to do the test. After multiple unsuccessful attempts it was finally determined that he needed a new fuel rail as there was a burr in the seating area on his old one.