Leaky injector or bad fuel pump check valve

[Gavin]

More often than not my 2001 gmc sierra 1500 wont start on the first crank. Second crank will always fire up without hesitation. I checked the fuel pressure and its around 55 psi at idle but as soon as I turn the truck off, the fuel pressure drops to 0. I’m trying to figure out if it’s the fuel pump check valve or a leaking injector. I confirmed that the fuel regulator is good. If the check valve failed I feel like the pressure would drop quicker than a leaking injector so I’m leaning towards the check valve but wanted to get some feedback since I’m just speculating. People online are saying to check the fuel pressure after pinching the return line but a braided metal line and not rubber. I was also wondering if I could check the fuel pressure where the fuel filter goes to bypass the injectors and isolate the fuel pump check valve. I know it would be easy to just slap a new fuel pump on it and see what happens but I want to try to diagnose it before I start throwing parts at it

 

[stutaeng]

My 99 sometimes does this but in the afternoon after sitting in the sun when I get off work. I haven't tried diagnosing it.

I did once cap the return line with a vacuum cap and hose clamp and the pressure jumped to like 80 psi and it held. That's when I did my V8 swap and I was messing with trying to start it even tho I hadn't removed VATS from the system. I really did that because I was curious since I was still on the original pump at 265k (I'm not at like 286k and still on the original pump.)

You can also pop the fuel rail and put some paper towels, prime the system and see if an injector(s) leak.

My truck had the 4.3 and I come from that "spider injector" system which is atrocious because you can't easily do these kinds of tests on that system, so the LS engine platform is very easy to troubleshoot in my opinion.

 

[Gavin]

My 99 sometimes does this but in the afternoon after sitting in the sun when I get off work. I haven't tried diagnosing it.

I did once cap the return line with a vacuum cap and hose clamp and the pressure jumped to like 80 psi and it held. That's when I did my V8 swap and I was messing with trying to start it even tho I hadn't removed VATS from the system. I really did that because I was curious since I was still on the original pump at 265k (I'm not at like 286k and still on the original pump.)

You can also pop the fuel rail and put some paper towels, prime the system and see if an injector(s) leak.

My truck had the 4.3 and I come from that "spider injector" system which is atrocious because you can't easily do these kinds of tests on that system, so the LS engine platform is very easy to troubleshoot in my opinion.

Yeah I think im gonna pop the fuel rails off soon to check for injector leaks. But yeah its been like that for at least year now and ive just dealt with it

 

[stutaeng]

Yeah I think im gonna pop the fuel rails off soon to check for injector leaks. But yeah its been like that for at least year now and ive just dealt with it

If you could go ahead and replace the fuel injector o-rings, that would be ideal. May be something like $35 shipped thu Rockauto.

O-rings may be brittle by now and since you are there, might as well do it. Just a thought.

 

[Gavin]

If you could go ahead and replace the fuel injector o-rings, that would be ideal. May be something like $35 shipped thu Rockauto.

O-rings may be brittle by now and since you are there, might as well do it. Just a thought.

I just did around a year ago when I rebuilt the motor. I’ll definitely take a look at them tho