[Chance26]

Vehicle 2003 GMC Sierra 2500HD 6.6 LB7

Just got done changing out the Fuel Injectors and New CP3, all back together and go to start it and nothing.

*Replaced the fuel system in the tank
*Replaced one of the hard fuel lines which I accidently snapped
*New ACDelco fuel filter
*Rebuilt the fuel filter head
*New clamps
*New CP3
*New Fuel Injectors
*New Water sensor on the bottom of the fuel filter
*Lift Pump on the way

When I put everything back together there where no weak, cracked, collapsed or kinked lines. Filled the fuel filter and primed the system, cracked the bleeder on the fuel filter until fuel was coming out and the truck started up and ran beautifully, better than it has in years (6 of the 8 injectors where clogged). Once the truck sucked the fuel filter dry it shut off. My question is what am I doing wrong? I've followed all the lines from the fuel filter all the way back to the tank, I don't see anything wrong at all. Fuel gets pulled out of the filter but none gets sucked back into it. Do I have a ton of air in my lines that I just haven't sucked out yet? I've a Lift pump on the way but I don't want to install it until I've fixed my immediate problem. I see fuel coming from anywhere from any hoses, under or on top of the engine. I'm stuck, if someone could point me in the right direction I'd be grateful!

 

[Stroked06Goat]

Gently pressurize the tank through the filler neck to help ? You may be sucking filter dry since you are pulling the rest of the air out of the lines? If filter going dry, there is simply not fuel replacing it, however that is happening. Outside of that, just recheck your work that the proper lines are connected to the appropriate spots etc.

 

[Stroked06Goat]

PS my 04 lb7 i ran it out of fuel once....that was NOT fun. My thumb was sore with how much priming i had to do

 

[Ron Nielson]

Any junction point in the fuel line from the tank to the fuel filter should be a prime suspect. You can get a handheld vacuum pump (mity-vac comes to mind) and create a vacuum at the fuel filter inlet - coming from the tank - and pull this with the vacuum and see if you get fuel. The amount of vacuum created by the truck's CP3 is pretty low and could be replicated with the handheld vacuum pump. If that fails, there's a junction point in the fuel supply line over the driver's side valve cover, so try there, and keep on going until you get to the tank. If your CP3 won't pull the fuel and the fuel filter primer won't pull the fuel, something's not right. Pretty hard to guess exactly where and what the problem is unless the truck is present.

OR

You could put a clear line at the fuel filter head and see what that shows you, air bubbles, some fuel, no fuel, etc. while the engine is cranking. You could also test the vacuum by using the test port on the inlet side of the engine, looks like an air conditioning valve/port.

 

[Chance26]

Well, found the issue.

Installed a Lift pump and found two leaks right away, fixed those up and primed the system. Truck starts for a nano second and then dies. Now With the loss of the power windows and such, turns out I threw a Security alarm with the start up system somehow and it cut power to everything. Had to disconnect the battery's for 30min and the re-connect them. Truck now starts up fine and runs like a champ, but since this is the first time I've had a chance to let it run since replacing the injectors and CP3 I've been chasing leaks. Found the last one last night, loose injector line was leaking all down the side of the case. So far that's it though, hopefully this project ends tonight when I get home and tighten that line!