2500HD 6.0 help...

2004 chevy 2500HD 4wd 6.0 4L80E 200k.

i just got it 2 months ago for a work truck, ran AWESOME on the trip home. one of my guys drove it for a couple days says it didn't have any ass. started to bog down under accel. i though it might be the trans, or something major. changed all fluids to amsoil. started looking at it and it feels like its missing under load, and starts poppin, sputtering. if you ease off it a little it runs fine.

i started thinking fuel pump/filter/regulator. it sounds like it was going lean. i hooked a fuel pressure gauge up and drove it. it holds 60psi at idle, dips to 40-50psi under light load, dives to under 20psi and lower with any more gas pedal.

i pulled the bed, and the pump. the tank is SPOTLESS. i checked voltage at the pump harness. its only getting 5v? is that right? the sender also get 5v but i didn't think much of that.

the replacement pump is $400 autozone or $175 rockauto

is the pump bad? does it run 5vDC? what do i do now?

jeez, i started looking into this. it looks like the computer sends variable voltage to the pump depending on load and pedal position?

anybody know wtf is goin on?

FYI this truck is SPOTLESS inside and out. still smells new. one owner fleet maintained.

Check the voltage as it runs. It could very well be a pump going bad and heating up and therefore dropping voltage. Or you have a wiring problem from excessive wiring resistance.

Have you swapped relays and rechecked voltage at the pump?

It is a returnless system, so it varies the voltage, which varies the pump output, to maintain emissions and performance.

If you're getting 5v to the pump, I wouldn't blame the pump. Its a 12v pump.

Fix the wiring first. You sure you tested the right wire?

Somewhere near the fuse/relay panel is a red test lead for the pump. Give it 12v there and see if you get 12v at the tank. If you don't, you've at least narrowed it down to where the problem might be.

Test voltage going into and out of the fuel pump relay. They sometimes take a partial vacation.

Ranger... after 2001 it should be a return system with a straight 12v to the pump... unless they changed back.

OK update...

its getting 12vDC on the gray wire of 4 blade fuel pump connector. it only gets it for a couple seconds with key on. this sounds right. it also gets 12v while cranking.

sounds like a bad pump, or clogged filter to me... anyone disagree?

curtis73 wrote: Ranger... after 2001 it should be a return system with a straight 12v to the pump... unless they changed back.

it is a returnless sysytem with a one piece in-tank pump/filter/regulator.

^^this is the cheapy pump...below is the $350 pump, it looks like my stock pump.

I assume no codes. Right?

I could see a APPS being bad, giving a wrong signal.

its got a CEL but i have no reader. i assume it throwing a missfire.

the fuel pressure is LOW when i drive it. it has to be something in the pump/filter/regulator...

If you look hard enough, the aftermarket has just pumps instead of buying the whole expensive thing. Those tank units snap apart very easily and I don't see why you couldn't put a Walbro 255 in it. We did that in a GM last year at the shop... forget what it was. Pontiac something.

OK cool i knew someone would have some ideas. what about the fuel filter? it seems like it could be the prob? is there a part number for it?

anyway UPDATE. i hooked it back up. check voltage at the pump in real time. 13.7 v idle. it still stumbled at spit while giving half pedal or more with the fuel pressure diving below 20psi. gotta be pump or filter right?

i would love some part numbers to find a filter and pump. i might just call around and get a used one for $50 at a JY

thanks for the help guys!

^^ hell yeah! thanks everyone!

Throttle Position Sensor?

its a bad pump

Could be a bad pump, but they usually work, or not at all. There shoul be another fuel filter besides the one in the tank. Probably along the frame rail or under hood.

the newer chevy pumps very commonly slowly fail.

I am with Katy but will also throw in the need to replace plugs with ACs and a set of Delco wires. 200K is a lot of opportunity to have the wrong parts installed.

ya plugs and wires are a must. before changing the plugs id rec running a quart of atf very slowly through a vaccum line followed by a pint of seafoarm

I use clear aquarium tubing with an in line valve, drill the transmission fluid cap so the hose barely fits through, add a small vent hole in the cap. Pipe the tubing into a vacuum line and start with no flow and slowly add the ATF until the clear line is carrying mostly ATF not air, run until the bottle is dry. Reuse the bottle to run the Seafoam.

well i just ordered $232 bucks worth of fuel pump, plugs and wires. i'll update when i get it fixed. should be tuesday night.

i (we) ordered the wrong fuel pump. new one came today. gonna replace it with plugs/wires tomorrow.

we'll see...

John Brown wrote: I use clear aquarium tubing with an in line valve, drill the transmission fluid cap so the hose barely fits through, add a small vent hole in the cap. Pipe the tubing into a vacuum line and start with no flow and slowly add the ATF until the clear line is carrying mostly ATF not air, run until the bottle is dry. Reuse the bottle to run the Seafoam.

OK, what does this do?

It cleans out an engine internally without taking it apart.

It will remove hard carbon deposits in the air intake tract, head combustion chamber.