Author Topic: 08 Silverado 2500HD 6.0Li - Random loss of fuel pressure  (Read 4950 times)

ling427ttvette

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08 Silverado 2500HD 6.0Li - Random loss of fuel pressure
« on: March 12, 2013, 09:46:51 PM »
I spent a ton of time trying to diagnose this thing, and the conclusion we came to after some phone calls isn't something I feel is right, so here's the run down:

The pickup comes in, guy tells us it's losing power and falling on it's face when you demand extra power, if you baby it, it's fine.

I hook up my code reader, mis-fire on cylinder 7 and system to lean bank 1 and 2.

Hook up my fuel pressure gauge and go for a drive, 58 or so lbs. of pressure on start up and drive. 15 miles out, it finally starts acting up. When asking for more power, the fuel pressure rapidly drops to 10 lbs., obviously going way lean which caused the codes.

So, I figure weak fuel pump and replace it. Take it for a 30 mile drive, it's fine. Guys come pick it up, they get about 40 miles out and it does it again.

So, again I hook up my fuel pressure gauge and it's doing the exact same thing. Only this time we discovered that if you shut the key off and re-start it, it resets itself and runs great for another 10-15 miles. Immediately I start thinking fuel pressure regulator, nope doesn't have one as it's a return-less system. So, I hop on Shopkey and it tells me there is a fuel system control module and a fuel pressure sensor, go look for them and no, nothing at all, does not have them. Go back and find out the fuel pressure sensor is for the E85 model only, and apparently the FSCM is for the model with a 4.3 (really doubt they offer a 4.3 in a 2500HD, but sure we'll go with it)

Anyways, I make a phone call to the dealership and have them poke around, they confirm it not having a FSCM or FPS, and tell me there is a bulletin for the Throttle Position Sensor and that a lot of the vehicles they replaced it on were having similar problems. I am having a hard time seeing how it's the TPS, but with the way they do things now a days I don't doubt it either. Any one have an experience like this and figure the issue out?
« Last Edit: March 12, 2013, 09:49:51 PM by ling427ttvette »

MiniVanMan

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Re: 08 Silverado 2500HD 6.0Li - Random loss of fuel pressure
« Reply #1 on: March 12, 2013, 10:27:45 PM »
I'll ask around at work tomorrow, see if it's a common problem. Sounds like it could be less of an engine problem and more of a transmission or PCM problem... but I'll get an opinion from some of the seasoned Chevrolet techs.

ling427ttvette

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Re: 08 Silverado 2500HD 6.0Li - Random loss of fuel pressure
« Reply #2 on: March 12, 2013, 10:38:22 PM »
I was thinking PCM myself, or whatever module controls the fuel system. Mostly because of it resetting it self after shutting it off and re-starting it. I keep thinking to myself there HAS to be a way for it to monitor fuel pressure so it can communicate with the computer and regulate the fuel pressure for the demand of the engine. It just seems strange to me that when driving normal, it's running 55-60 lbs. of pressure, but as soon as you press down more on the accelerator the fuel pressure drops almost instantly. But, before it starts acting up you can drop the hammer and it holds 55-60 lbs steady and runs great.

MiniVanMan

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Re: 08 Silverado 2500HD 6.0Li - Random loss of fuel pressure
« Reply #3 on: March 12, 2013, 10:40:22 PM »
Does it do the same thing in neutral (park) and free revving, or only when there's a load on it? Also, how's the fuel filter?
« Last Edit: March 12, 2013, 10:42:48 PM by 00XJ »

ling427ttvette

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Re: 08 Silverado 2500HD 6.0Li - Random loss of fuel pressure
« Reply #4 on: March 12, 2013, 10:45:08 PM »
Seems to do it only when under load. No in-line fuel filter either.
« Last Edit: March 12, 2013, 10:45:51 PM by ling427ttvette »

MiniVanMan

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Re: 08 Silverado 2500HD 6.0Li - Random loss of fuel pressure
« Reply #5 on: March 13, 2013, 11:49:33 AM »
Fuel pressure regulator is in the tank with the fuel pump apparently.

Kalgorn

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Re: 08 Silverado 2500HD 6.0Li - Random loss of fuel pressure
« Reply #6 on: March 13, 2013, 03:10:59 PM »
Look in to the fuel pressure relief valve. I don't know 100% if that generation has one. My dad has an '02 with the 6.6L turbo diesel and he was having issues where, under load, the truck would drop in to limp mode where it would lose all power but he would be able to coast to a stop on the side of the road. Turn the truck off for 30 seconds, then it turns on just fine. A couple forums were pointing him to the FPRV which, over time, wears out and eventually can pop false positives.

It turned out that wasn't his issue at all. It was actually the fuel pump. However, it's something to consider. The problem you're describing sounds very familiar.
« Last Edit: March 13, 2013, 03:12:13 PM by Kalgorn »

2002 Silverado | 1995 Talon TSi AWD | 1989 Prelude Si 4WS

ling427ttvette

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Re: 08 Silverado 2500HD 6.0Li - Random loss of fuel pressure
« Reply #7 on: March 15, 2013, 01:22:51 PM »
Havent had a chance yet, but I'm not entirely sure it has a relief valve. I do know the fuel system from the diesel to the gas engine is very different as far as components. Sounds like my boss is wanting to just haul it to the dealer and get the TPS replaced under the recall and see what happens. If anything, have them diagnose it while it's there and then I can just do whatever it needs.

Being a mechanic for the state keeps a guy damn busy, we've got so much new equipment to prepare, on top of all the shit breaking down that we have to send a good amount of work off to other places, and we have 3 full time mechanics at our shop, plus 2 in the panhandle. We fix all state equipment in a good portion of Northwest Oklahoma. Thousands of pieces of equipment, from chain saws to road graders and plenty more.