P0087 plus fuel filter problem

[DeathStar2008]

A couple weeks back, I was pulling a 10K lb car hauler through the hills around Chattanooga TN when the truck dropped to limp mode. About a half hour before that, the computer started telling me to replace my fuel filter, which was still fairly new. I turned the truck off, then cranked it, and the problem went away for the next three days, until we hooked up the hauler again to come home. Then the same thing happened. About an hour and half into the trip, it tells me to change the filter, then a little while down the road... limp mode. I stop, re-crank, problem goes away. First thing I do when I get home is replace the fuel filter AND sensor, which seemed to fix the problem, but we have another car show coming up in Illinois in a few weeks, so I take it in to have the injectors tested. Injectors turn out fine, but the guy tells me the fprv has gone soggy and rail pressure was dumping from 26K to 14K. I replace it, and all seems good, until one day I'm driving and it happens again. REPLACE FUEL FILTER, then a few miles later, limp mode. Only this time, the truck wasn't hauling anything. Any ideas?

 

[JoshH]

How did the guy test the injectors, and how did he determine the FPRV was bad? There's a lot to diagnosing a problem like this, and to do it right, you have to have some tools that most DIY mechanics and even some shops don't have. The first thing I would do is hook up a fuel pressure/vacuum gauge to the test port next to the alternator. You need to see if there is a restriction in the line. If that passes, do a bottle test to determine if the FPRV is bypassing fuel to the return side. I always run this test at idle and just use a scan tool to raise rail pressure to max. It also allows me to see if the pump is in good shape. Unless it has a huge leak on the high pressure system, a good pump shouldn't have a problem reaching 26k psi of rail pressure at idle. If you don't get a bunch of fuel in the bottle during your bottle test, you will need to run the return rates on the injectors. This will tell you if you have one or more injectors returning too much fuel to the tank. Unfortunately, there isn't an easy way to do this. Running through all that should pinpoint where your problem lies. Good luck.

 

[Burn Down]

^^^ As Josh mentioned... But real quick easy check is to see if the Fuel lines are collapsing next to the transmission & the bottom of the cab at the firewall. Anywho my dads truck has the same issue as you just described, I'm positive this is the problem. I just need to get home to Idaho to fix it for him.
Here is a gm service letter on the issue.
#PIP4526: Diesel Engine Fuel Line Repairs - keywords DTC hose kink loss P0087 P0093 P1093 pipe power reduced repair restrict restriction SES suction supply vacuum - (Nov 7, 2008)


Subject: Diesel Engine Fuel Line Repairs


Models: 2001-2007 Chevrolet Silverado Classic

2001-2007 GMC Sierra Classic

2007-2009 Chevrolet Silverado

2007-2009 GMC Sierra

Equipped with the 6.6L Diesel Engine RPO codes LB7 LBZ LLY LMM




--------------------------------------------------------------------------------

The following diagnosis might be helpful if the vehicle exhibits the symptom(s) described in this PI.

Condition/Concern:
A dealer may need to perform a repair on the rubber portion of the fuel supply (suction) lines. The rubber section of the line could become kinked or collapse. Fuel lines that kink or collapse may induce a fuel system restriction (high vacuum gauge readings) or DTCs P0087, P0093, and/or P1093 to set.

If a technician was to suspect the rubber portion of the fuel feed line collapsing or kinking, replacement of only the rubber line is acceptable.

Recommendation/Instructions:
Complete the steps below to repair the rubber section of fuel supply line:

Carefully cut, split, and remove the OEM crimp from both ends of the flexible hose. These crimps can be cut with a small cut-off wheel. Split the crimp into two pieces (use your discretion on first cut location, then cut directly across from, or 180 degrees from first cut). Special care must be taken not to damage the flare on the end of the steel pipe that will be reused.
Remove the OEM crimps and flexible portion of hose from the existing supply line.
If replacing the rubber section of the supply line, a 1/2 ID hose meeting SAE specification 100R3 is suggested. Dealers may be able to find a local supplier for this hose, or can contact the manufacturer Parker Hannifin. The replacement hose would be a 1/2" diameter Parker part number 601-8 or H017-8.

 

[DeathStar2008]

Thanks guys. I know they used the vacuum gauge, and drove it with the computer hooked up until they recreated the problem. I'm no mechanic, but after doing some research when this first started happening, I deduced it was the fprv, and passed that along to them when I took the truck in. I didn't mention the fuel filter at that time, because I believed it was a separate issue, since this was the third filter it's done this to me with, and it just now started dumping to limp mode. I figured it was the fuel filter sensor, so I replaced that too, when I changed the filter two weeks ago. The mechanic thinks it may be the low-side fuel pressure sensor, but I can't find the damn thing. I will check the fuel lines under the truck to see if I can find a crimp.

 

[Burn Down]

No low pressure sensor...
Post #2 in the below thread explains how the filter minder works.
http://www.duramaxdiesels.com/forum/showthread.php?t=56508

 

[DeathStar2008]

That explains that. He did say he wasn't sure if the LMM had it or not. I checked the lines all the way from the tank to the fire wall, and they all look good. All hard lines with the exception of two bends that are braided with plastic covers.

 

[DeathStar2008]

These don't look crimped to me.

 

[Burn Down]

You want to look real close at the soft portion of the line bud... I haven't got home to look at dads truck yet but I'm positive the rubber sections are sucking closed under load.