6.0 Engine Question

icecoldtexan · May 24, 2008

A while back I noticed my truck wasn't starting up as quickly as it used to, seemed like it took a few more revolutions until it started, and the idle seemed a little rough, so I checked my DTC codes and had a P0131 code stored in memory, I swapped my front os sensors with each other to see if I would get the code for the other bank trying to narrow the problem to a specific os sensor. Didn't get the code again until last week while pulling a camper I noticed a loss of power on acceleration, it was very sluggish on hills, rough idle, it seems to have a surge in power when I hit about 3000 rpms, I checked my fuel pressure at the schrader port in the fuel rail and have 50psi when not running and it doesn't bleed down, I have 50 psi when idling, and when I depress the accelerator the pressure goes to about 65 psi.

Any ideas what to check next before I have to take it to the dealer ? Is 50 psi the correct pressure for the fuel. Can it be the intake gasket leaking ? clogged injectors ?

I replaced the fuel regulator and fuel filter last year when I changed my plugs and wires.

Thanks,

Perry

2001 silverado, 2500hd, 6.0, 130000 miles, all stock

icecoldtexan · May 24, 2008

A while back I noticed my truck wasn't starting up as quickly as it used to, seemed like it took a few more revolutions until it started, and the idle seemed a little rough, so I checked my DTC codes and had a P0131 code stored in memory, I swapped my front os sensors with each other to see if I would get the code for the other bank trying to narrow the problem to a specific os sensor. Didn't get the code again until last week while pulling a camper I noticed a loss of power on acceleration, it was very sluggish on hills, rough idle, it seems to have a surge in power when I hit about 3000 rpms, I checked my fuel pressure at the schrader port in the fuel rail and have 50psi when not running and it doesn't bleed down, I have 50 psi when idling, and when I depress the accelerator the pressure goes to about 65 psi.
Any ideas what to check next before I have to take it to the dealer ? Is 50 psi the correct pressure for the fuel. Can it be the intake gasket leaking ? clogged injectors ?

I replaced the fuel regulator and fuel filter last year when I changed my plugs and wires.

Thanks,

Perry

2001 silverado, 2500hd, 6.0, 130000 miles, all stock

Ok, I just checked fuel pressure again, engine running pressure is 50, when I pull vacuum hose off regulator the pressure goes to 60. I turn the truck off and pressure starts to bleed down, watched for 3 minutes and it went from 50 to 38. Any ideas ?

Fortune50 · June 3, 2008

I wouldn't replace the fuel pump just yet. Unplug the regulator vacuum hose and be sure it doesn't leak fuel. If that's ok, here's the specs on the '01 6.0 fuel pressure:

55-62 psi w/ the engine off, scan tool commanding fuel pump to turn on. Don't forget to purge air out of the gauge by depressing on the air bleed button on your gauge while the pump is running or you may get a bad reading.

The spec for after the pump stops running is once the pressure stabilizes (takes only a second), then monitor for 1 minute, should not drop more than 5 psi.

Then check again by bleeding off pressure until the gauge reads 10 psi, then monitor for 5 minutes, should not drop more than 2 psi.

You've already done the test of the regulator, it looks like it rises 10 psi when you disconnect the regulator (you said it read 60 from 50 psi). The spec is a 3 to 10 psi rise. So that looks good. Just be sure it doesn't leak fuel out the vacuum port.

It kind've sounds like you may have an issue w/ pressure being unable to pump up during the 2 second pump prime (when the keyswitch is turned from OFF to ON). It should read 55 psi, it may take a few turns of the keyswitch to get it. Or you could jumper the fuel pump relay terminals to make it run at the underhood fusebox-use a 20 amp fused jumper. Just be sure to purge out all the air of the gauge, may want to repeat the engine OFF pressure test again before looking further. If it can't get above 50 psi, may want to look at the voltage reading of the connector to the fuel pump. Probably only accessible by dropping the tank, though. At that 4 wire connector, the power wire to the pump is gray, the ground is black. As a quick test of the fuel pump relay, you could swap relays with another exact one in the fusebox. Good luck.

icecoldtexan · May 30, 2008

A while back I noticed my truck wasn't starting up as quickly as it used to, seemed like it took a few more revolutions until it started, and the idle seemed a little rough, so I checked my DTC codes and had a P0131 code stored in memory, I swapped my front os sensors with each other to see if I would get the code for the other bank trying to narrow the problem to a specific os sensor. Didn't get the code again until last week while pulling a camper I noticed a loss of power on acceleration, it was very sluggish on hills, rough idle, it seems to have a surge in power when I hit about 3000 rpms, I checked my fuel pressure at the schrader port in the fuel rail and have 50psi when not running and it doesn't bleed down, I have 50 psi when idling, and when I depress the accelerator the pressure goes to about 65 psi.
Any ideas what to check next before I have to take it to the dealer ? Is 50 psi the correct pressure for the fuel. Can it be the intake gasket leaking ? clogged injectors ?

I replaced the fuel regulator and fuel filter last year when I changed my plugs and wires.

Thanks,

Perry

2001 silverado, 2500hd, 6.0, 130000 miles, all stock

Ok, I just checked fuel pressure again, engine running pressure is 50, when I pull vacuum hose off regulator the pressure goes to 60. I turn the truck off and pressure starts to bleed down, watched for 3 minutes and it went from 50 to 38. Any ideas ?

Does fuel pressure bleed down imedatly with key on engine off? You can check this have a friend help check fuel pressure this way have person under truck with good pair of needle nose pliers have someone turn the key on and crimp the fuel line under the truck soon as the fuel pump primes up and see if the fuel pressure still bleeds down any? If not then u could have a bypassing fuel pump or the little hose connecting the fuel pump in tank could be leaking, if it bleeds down still when line is crimped good then u have a leaky injector possibly. But also the fuel pump could be flowing poorly also but have goos pressure, the miles on the truck can prove that too.

Is 50 psi fuel pressure at idle within specs ? I did watch the guage while I drove and the pressure rises to about 60 psi max. Can it still have low flow and have 60 psi while driving? Can it still be a bad/leaking fuel pump. I guess it probably wouldn't be a bad idea to change the pump anyway due to the mileage, probably on it's way out anyway.

shanzr · August 5, 2008

dont know if you resolved your problem, but if not... i had same prob with mine, even the gas gauge wasn't reading correct. wouldnt start on first turn, sluggish up hills pulling load with check engine light flashing, rough idle. so went ahead and had bed of truck hoisted and replaced fuel pump ($300), corrected all problems, even gauge read correct again.

silveradobobby · May 26, 2008

A while back I noticed my truck wasn't starting up as quickly as it used to, seemed like it took a few more revolutions until it started, and the idle seemed a little rough, so I checked my DTC codes and had a P0131 code stored in memory, I swapped my front os sensors with each other to see if I would get the code for the other bank trying to narrow the problem to a specific os sensor. Didn't get the code again until last week while pulling a camper I noticed a loss of power on acceleration, it was very sluggish on hills, rough idle, it seems to have a surge in power when I hit about 3000 rpms, I checked my fuel pressure at the schrader port in the fuel rail and have 50psi when not running and it doesn't bleed down, I have 50 psi when idling, and when I depress the accelerator the pressure goes to about 65 psi.
Any ideas what to check next before I have to take it to the dealer ? Is 50 psi the correct pressure for the fuel. Can it be the intake gasket leaking ? clogged injectors ?

I replaced the fuel regulator and fuel filter last year when I changed my plugs and wires.

Thanks,

Perry

2001 silverado, 2500hd, 6.0, 130000 miles, all stock

Ok, I just checked fuel pressure again, engine running pressure is 50, when I pull vacuum hose off regulator the pressure goes to 60. I turn the truck off and pressure starts to bleed down, watched for 3 minutes and it went from 50 to 38. Any ideas ?

Does fuel pressure bleed down imedatly with key on engine off? You can check this have a friend help check fuel pressure this way have person under truck with good pair of needle nose pliers have someone turn the key on and crimp the fuel line under the truck soon as the fuel pump primes up and see if the fuel pressure still bleeds down any? If not then u could have a bypassing fuel pump or the little hose connecting the fuel pump in tank could be leaking, if it bleeds down still when line is crimped good then u have a leaky injector possibly. But also the fuel pump could be flowing poorly also but have goos pressure, the miles on the truck can prove that too.