problem...

[KongGMC]

I have a 2003 GMC Sierra with the 4.8 engine and auto tranny. I've been experiencing an unusual problem for some time now and so far everyone hasn't a clue.

Basically, if I drive the truck for say 20-30 minutes straight, then park it for about an hour or two, it will stall out when I go to crank it up. I can crank it again the second time and it will usually start up and bog for a second then it's fine. Sometimes it takes the third time to get it to start. Once it's started it runs like a champ. It'll only do this in these exact conditions however.

Several people have said they experienced this same condition and after replacing the fuel pressure regulator the problem went away. I've replaced mine twice now and am still experiencing the problem. The fuel pump does not whine and I have had this problem for several months now so I doubt it's the pump. One guy in the chat room suggested it could be the fuel relay or Crankshaft Position Sensor. Any ideas would be GREATLY appreciated! Thanks.

[RedHeartbeat]

put a fuel pressure gauge on the service port at the engine fuel rail. Start the truck and check fuel pressure. Should be 52-62 PSI. Leave the gauge on the fuel rail and shut off the engine and wait. It should hold pressure for about 30 minutes. If you lose pressure you have either dirty injectors or a bad fuel pressure regulator. This is a single fuel line fuel rail, correct? The FPR would be in the fuel tank fuel pump assembly, if so.

[KongGMC]

The fuel pressure regulator is mounted on the driver side fuel rail.

And also, if there was a problem with it holding fuel pressure, why is it that after I drive it 30 minutes and then leave it sitting over night it cranks right up on the first try in the morning? I just don't understand how it could be fuel related cause it definately has to be exactly under the conditions I previously stated.

I guess I need to go invest in a fuel pressure tester and plug it into the fuel rail before I start it when it is in the condition to do this, that way I know what is going on in there.

[RedHeartbeat]

Overnight, the fuel that would drain into the cylinders would evaporate or creep past the gaps in the rings and end up in the oil.

[KongGMC]

So no other ideas until I've had a chance to buy a pressure tester and monitor the fuel pressure huh?

Has anyone else had a chance to try out a Borg Warner fuel pressure regulator? Don't know if maybe these just suck and both of them that I've bought went bad real quickly possibly. It'll be another week before I can afford to buy a fuel pressure tester so I guess I'll have to play the waiting game for now.

[ff_jeff]

go to a shop and have them test the fuel pressure. I agree with red, Also might think about MAF. Although it sounds like Fuel pump, fuel filter, fuel relay, or pressure regulator.

[onefastaSSchevy]

i think its fuel related, not too hard to check, i would def. get a gauge on the service port to see whats going on in there

[KongGMC]

Well I bought a fuel pressure tester but I haven't had a chance to test the truck yet. I'm gonna test it probably either tuesday or wednesday and see what happens.

I did want to ask another question though. Today after work I parked the truck for about an hour or so and I went out and started it up and it was fine. I went back in the house to get something and when I came back out the Check Engine light was on. I checked the light at work and it just said Evaporative Emissions Control System malfunction(small leak detected). It has kicked this light on before when having a problem starting. What all should I check besides the obviously replacing the gas cap? Also is it possible this could have anything to do with my starting issue?

[ff_jeff]

gas cap... thats what the evap crap is... tighten or get a new cap

[KongGMC]

I put the fuel pressure tester on the fuel rail and tested it today. I hooked it up and started the truck, the pressure idleing was about 51 or so and when I turned it off, it dropped to about 49 and slowly (after about 20-30 seconds) dropped down to 48. I ultimately just took it off. I was pretty sure this means it failed the test but I don't know if maybe I did something wrong so I wanted to ask you guys what the exact process should be, i.e. how long should it run, should the truck be driven for a bit first, should you drive around with the guage hooked up???? Let me know guys, thnx.