Random Hesitated/stumble on start-up

[SAATR]

SAATR, thank you for the lengthy response. You make some real good points, and as much as it makes sense, I Really hope it's not a leaky injector(s)... Lol
I knew the factory injectors are crap by design and researched that the ls1 injectors make for a great substitute after the computer is tuned to match. When I have a chance to rent that fuel pressure gauge again, I will try what you recommended.

Just trying to shed some light on the subject. Oh, about the fuel pressure test gauge:

http://www.ebay.com/itm/New-Fuel-In..._Automotive_Tools&hash=item5ae5546cb5&vxp=mtr

$27 shipped to your door from Pomona. Nifty case too!

 

[BOTTLEDZ28]

My 94 does this about once a week and it is ALWAYS on a warm start up. I have a mechanical fuel pressure gauge mounted inside my truck to monitor the pressure and 100% of the time it does it, the fuel pressure will be between 6 and 9. I have it set at 12.5. It goes away about 2 minutes later as the pressure slowly builds up again. It never does it on a cold start and the pump is new as of 2 years ago. I suspect that either the pump is going bad or there is something weird going on with the voltage to the pump.

If I were you, I would monitor the fuel pressure for a while to get an idea of what it is doing. if it checks out then at least its one less thing you need to look into.

 

[97SilveradoHD]

Just trying to shed some light on the subject. Oh, about the fuel pressure test gauge:

http://www.ebay.com/itm/New-Fuel-In..._Automotive_Tools&hash=item5ae5546cb5&vxp=mtr

$27 shipped to your door from Pomona. Nifty case too!

I appreciate that, and that's a hard deal to pass up on. Might have to put my order in for that guy, wonder if it'll reach the cowl?

My 94 does this about once a week and it is ALWAYS on a warm start up. I have a mechanical fuel pressure gauge mounted inside my truck to monitor the pressure and 100% of the time it does it, the fuel pressure will be between 6 and 9. I have it set at 12.5. It goes away about 2 minutes later as the pressure slowly builds up again. It never does it on a cold start and the pump is new as of 2 years ago. I suspect that either the pump is going bad or there is something weird going on with the voltage to the pump.

If I were you, I would monitor the fuel pressure for a while to get an idea of what it is doing. if it checks out then at least its one less thing you need to look into.

All this electrical BS drives me nuts... my 74 c10 with a good ol' edelbrock 600 carb starts beautifully everytime i hit the key, no lag, no hesitation, hot or cold. what happened to K.I.S.S.? ugh...

 

[SAATR]

The long hose should be the proper one for our trucks. Combined with the length of the hose that is attached to the gauge should be at least 2 feet, which will reach from the test port to the cowl on a 5.7L. A 7.4L, I don't really know where the fitting is.

 

[97SilveradoHD]

The long hose should be the proper one for our trucks. Combined with the length of the hose that is attached to the gauge should be at least 2 feet, which will reach from the test port to the cowl on a 5.7L. A 7.4L, I don't really know where the fitting is.

the test port on the 7.4 is on the front of the intake manifold, behind the thermostat IIRC.
It's been in the 90's here today and i've been driving around town making several stops for mother's day. Every time I've hopped in to restart the truck I KOEO and let the pump prime then start it, seems to be starting fine. But this could also be a weird coincidence...
BTW, the last time i changed the FPR (roughly a month ago) i looked for signs of an injector leaking down and didn't see anything. I also primed the system with the upper plenum off several times, looked and smelled for leaking fuel but didn't find anything....

 

[97SilveradoHD]

Is is possible that the ignition module is getting heat soaked? Or maybe it's worn out? Just seeing what you guys think...
I haven't checked the fuel pressure yet, but it seems that KOEO prior to starting the truck doesn't really help

 

[JonZ71]

Mine does this all the time. I think it's the poppets leaking down. I can look down in the intake and see a little bit of fuel laying around.

 

[1997chevydriver]

Is is possible that the ignition module is getting heat soaked? Or maybe it's worn out? Just seeing what you guys think...
I haven't checked the fuel pressure yet, but it seems that KOEO prior to starting the truck doesn't really help

I have thought that to and everytime i get a fuel gauge on it I cant get it to act up

 

[1997chevydriver]

Mine does this all the time. I think it's the poppets leaking down. I can look down in the intake and see a little bit of fuel laying around.

I have looked in mine and can't see or smell anything.

 

[JonZ71]

What i've always done is start it and let ir run for a min then shut it of. take the intake tube off first though and then whe nyou shut it off go open the throttle body and look at how much fume and mist comes out