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2005 GMC C4500

Maggard

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It's losing prime.....it will start and run.....you can drive it 10 miles down the road and all of a sudden it will start acting up.....it acts like it is starving for fuel...the filter loses prime.... you can pump the filter and get it back going!!!! But it will go a few miles and do it again. I've put a new filter housing,fuel pump,all new fuel lines on the engine,2 new fuel line from the tank to the engine.
 

WarWagon

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Wix plastic fuel filter on it by chance? Any codes? A loss of prime may trigger a low rail pressure and limp the engine.
 

Maggard

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I've used 3 different band filters and the code is low fuel rail pressure.....I'm having no luck finding the problem.
 

WarWagon

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Fuel smell like gasoline, have any water in it, look or smell funny in any way? Cut open the first oldest filter that gave you trouble - may give you a hint...

Fuel heater working aka a fuel Gelling problem?

Have you dropped the tank? Maybe leak internal to the pickup assembly. I forget if and what kind of screen is in the tank.

At this point, before tank droppage, I would feed it from a 5 gal pail (can whatever) of diesel to eliminate the tank as the source of the problem. 10 miles down the road - forget it! Load it in place in the shop/garage...

New parts don't mean good parts. Not the first or the last time a filter o ring got doubled up.

Do you see any damp lines or connections at all? Air, suction, leaks may not leak fuel, but are a dead giveaway if the do.
 

Maggard

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the other day they put another new fuel line on it drove it about 50 miles and it started acting up again....we have checked the tank....its really got us puzzled because we have checked all things that could be the problem its been broke down for about 4mo when it first started acting up you could be driving and it would all sudden lose power and wouldn't take fuel you could get out and pump the filter up and it would run fine....but I'm going to try what you said about feeding it from a 5gal pail and see what happens I've had a diesel mechanic look at it but still can't find the problem
 

WarWagon

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Give up and throw a lift pump at it? I am not fond of the primer fuel filter mess as it has been a weakness on the GM Duramax implementation: 1) Suction leaks aka GM to damn cheap to use a the cheapest problem lift pump they can find like everyone else. 2) Fuel filter assembly cracks, blows a seal, or otherwise has a suction leak. This includes the WIF threads leaking air or falling out on said piss poor plastic Wix fuel filter redesign from the AC Delco OEM design.

The "pressure" and 5 gal pail all eliminate a suction leak. Maybe a clear return hose off the CP3 to look for air could help.

Other possibility is a sticking FPR on the CP3 or a high return rate from a bad injector or overflow valve. (Aka high pressure leak.) Engine oil diluted with diesel?

And again contaminated with gasoline diesel fuel from "The Three Stooges" fuel delivery company or other fuel problems... What does the current fuel look and smell like?
 
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