This morning went to turn the truck on and it was giving me a loooong crank. Just would not start at all. Let off the key and gave it a few seconds and it fired right up but was extremely choppy and low RPM. Walked away to let the truck warm up a second and when I come back it revs up on its own and steadies out, sounds like it dropped back down after a few seconds though. Tried to drive it down the street and it did not want to move at all. I would press the gas and it would lag almost, sputter and surge forward after a second. Put the truck back in the driveway very slowly and turned it off, walked around the truck and there was some white smoke coming out of my tail pipe.

Sounds very un-fuel pump like but that's the only thing I can think of.




On the positive side this has lit a fire under my *** to get the Impala running again, need that extra vehicle.

 

Nothing like a project vehicle starting to break to make you fix your other project vehicle.

Any codes or CEL? Check the oil and coolant levels?

 

No CEL, didn't have time to check codes or oil and coolant levels, temp looked good on the gauge and so did oil pressure. Popped the hood for a quick second to see if anything just obvious was poking out, no oil or coolant anywhere in the engine bay.
There was a puddle of **** on the floor but I have no idea what that was, may have been my AC dripper or something else. Had to get to work so left it.

Not a lot to go on but it's what I got right now lol I have a laser operation at 11 for both of my big toes and I should be able to check some stuff out when I get home. Going to be a cripple for about a week though

 

Attached is my HPTuner's log of course my AFR gauge won't get picked up right now and I am not sure why but this should give a good starting point.

Coolant looks good and oil is beautiful. It is definitely a fuel issue I am also certain of it. The truck refuses to start the first time, doesn't sound happy when starting the second time and after it starts running it may rev up on it's own to get some RPM. In this log I revved it by hand though. When watching the gauge in front of my face it wants to idle at about 18+ AFR, which is okay I guess as this is somewhat normal but it just sounds awful and like it is going to keel over any second.

I am thinking some sort of vacuum leak must be going on here. I don't have a smoke tester so I may have to go buy one or create one.

Edit: No codes.

 

Picking up a fuel pressure gauge at Harbor Freight tomorrow after work. Planning on testing the fuel pressure to see if it is the pump or the regulator. I'm almost certain it is one of those two.

 

Can't you just log the fuel pressure? Or scan it while cranking or running?

 

@smokinlmm To my knowledge you can only check fuel pressure mechanically on a GMT-800.

I could try but that’s how I’ve always been told to do it so I never tried.

 

Ok my bad. I never had a gas gmt800 just Duramax trucks and they had fuel pressure sensors.

 

When I installed this engine 2 years ago I remember that I had to cycle the injectors with a scan tool and I am almost positive I had to read out the pressure manually even then.

 

Yep no way to check fuel pressure via scanner, I’m still on team it’s not getting fuel.