I swear, I've had nothing but issues with this truck!!! I have a 96 GMC XCab with 5.7 / Auto / 2WD.

HOLY $HIT, where to start....

I am getting air, spark and fuel, but it's not starting... all the time. When I can get it to start, it run good, but still gives issues.

Most of the time, if I can get it to start, it will start for the rest of the day... most of the time, but as it sits overnight, something happens and by the time I go to start it, the next day, it's a crap shoot if it will start.

Now, the issue of not starting seems to of gotten worse, over the past few days... today it would not start unless fuel was poured into the TB, then when you give it gas, it would either catch and stay started, die out, or run, then stall out when you give it throttle.

We think part of the issue might be the Fuel relay, because the other day, we messed with it and it was hot, but the truck started when we plugged it back in... in fact... well let me backtrack a little... When you try to go WOT and hit 3000 RPMs+, the motor would scream and it sounded as if the trans was in neutral and would not accelerate... Okay... now back to the fuel relay... the other day when the HARD START started, like I said, we messed with the relay and it "seemed" to of fixed the B.S. and it even "seemed" to of fixed the WOT issue, because when I went 3000+ it actually pulled all the way to 4000+... I was like HOLY ****, I have power now, past 2500!!! But then today, it is a NO START all day!

If I am getting spark, fuel and air, then what would be the issue? Like I said, today it would not start on its own, unless we poured some fuel into the TB, but then, it would either start then stall out, or start ad stay started until you gave it some throttle.

I'm fricken dying here, because this is my business truck and I need it running!!!


PLEASE HELP!!!!!!!

 

Had one a couple of years ago that did that. I found the timing cover had gone out of spec a few thousandths and caused the crank sensor to not pick up properly (missing rotations or triggering when it wasn't supposed to).

I'm assuming you've done all the basics like putting a pressure gauge on it and making sure it has fuel?

 

Yeah, it's getting fuel and spark. We pulled the cap and rotor, madesure the plugs and wires were good, etc, but still scratching our head. I am sending it to a shop tomorrow.... SCREW IT!!!

 

You almost surely have marginally low fuel pressure. The small block Vortec is extremely finicky about starting if the pressure drops just a few psi. Spec is 58~62 and it will vary from truck to truck, but usually once you start getting into the low 50's, that's enough to cause it to fail to start. Check it with a gauge.

The fuel pump relay can be problematic too, because it tends to burn up the socket in the convenience center. The thing is though, it got that way because it was powering a dying pump that is drawing excess current. Chicken/egg thing going on there.

Richard

 

This ^

I had a 1996 C1500 ECSB with similar issues. I replaced the FP and put two new sockets on the wires for the relay. Problem solved. About two months later, I had a loss of power and back firing, two of those stupid injectors on the spider went bad. Most likely unrelated, but seemed a bit suspect. My truck had around 135K miles when all of this started happening.

 

Funny you say that about the relay! One of the sockets on the side with 2 pins, the pin nearest the firewall, looks melted and the female pin in it is VERY loose.

 

It's a real sore spot on the Vortec trucks. More than once I've been tempted to instead of repairing the existing socket, to replace it entirely with a different design off to the side. The old large relay setup the TBI trucks had never burned up, but I've never compared the specs to know if it's an appropriate substitute for use with the other pump.

Richard

 

Thanks for all the help and suggestions, guys! Come to find out, it was the fuel pump; it was pushing out only 35 PSI so it wasn't getting proper pressure to the Poppets so to get fuel.

Thanks again all...!