1996 c1500 5.7L - crank no start

[nbkk43f]

Ok, it's time for the experts! My extremely reliable 96 pickup (~90k miles) has decided to not start. The truck doesn't see many miles and is mostly used around our property, not uncommon for it to sit for weeks without use - regardless, he always starts right up. I went to move it the weekend before last, it started right up, I put it in reverse and it wouldn't take any fuel and just shut off. Tried a restart, nothing.

I got it over to my shop and figured it was the fuel pump (i put a cheapo in it when I replaced it back in '19). Checked the fuel pressure, goes to about 45psi when I turn the key on and maintains it - when cranking it goes up to around 55psi.

I shot some fuel down the throttle body, hit the key and it fired up (briefly), so that eliminated "no spark". I also checked for codes (CEL isn't illuminated) and it came up empty.

I tried a new ignition control module, no luck. I then started doubting the fuel injection (spider) assembly and fuel pressure regulator. Pulled the plenum (fun job) and removed the FI assembly, cleaned everything up and replace the fuel pressure regulator while I was in there. I'm a carb guy so bare with me on this...I put 12v to each one of the injectors in the assembly and they all clicked as if they "work", besides why would all 8 go out all at once anyway?

Put everything back together and insured all the sensors were plugged back up. Crank, and still nothing.

So now lets start swapping out some parts...first on the list was the crankshaft position sensor, nope, still no start...

Throttle position sensor - nope...
Idle air control valve (why not) - nope...

So maybe I'm not getting any voltage to the main FI harness - I unplugged that and tested a few of the injector connections for voltage on crank, all that I checked had 12+ volts. For giggles I shot some more fuel down the carb to see if it would crank - yep, popped right off.

At this point, I'm at a loss and would greatly appreciate your thoughts!

Thanks in advance!

 

[Edelbrock]

So the injectors are working and you have fuel pressure, but your not getting fuel? There must be a filter somewhere that's plugged.

 

[Edelbrock]

Oh, wait - How is the fuel quality? This could simply be water in the fuel. Or diesel in the gas tank.

 

[nbkk43f]

So the injectors are working and you have fuel pressure, but your not getting fuel? There must be a filter somewhere that's plugged.

Thanks, there's only one filter and it's before the schrader valve for testing the fuel pressure, so given the pressure I'm getting, it should be fine.

 

[nbkk43f]

Oh, wait - How is the fuel quality? This could simply be water in the fuel. Or diesel in the gas tank.

Fuel seems to be fine, has a full tank, filled it up about a month or so ago. Smells like gas, no diesel.

 

[Ricko1966]

As I remember it anything less than 50 psi will cause a no start on a Vortec engine. It's been a while,but when these were common,I remember this being a problem. It's not that they run bad with low fuel pressure. They won't start.

 

[Long Rider]

You might try a voltage drop test. First go straight from pos to neg on your batt. It should be a little over 12 v. then measure the voltage by going from the pos on the batt and put the neg cable from the meter to someplace like the intake manifold. There should be very very small drop ie 1/10th v or less. If its more than that I would start checking ground wires. Just a thought.

 

[77Dmax]

It needs 58 psi to start.

 

[HotWheelsBurban]

It needs 58 psi to start.

Yes, also needs a good battery and distributor cap and rotor. If the cap and rotor look like this, it's "time for a change"....
This is off my '97 C3500 Vortec one ton, truck actually ran pretty decent with these parts. Ran a LOT better with a new cap, rotor and wires though!
The United Motor Products cap and rotor set are around $30 at Rock Auto, well worth the investment.

 

[Edelbrock]

Any update on this? If you start it on starting fluid, will it stay running?

Side note:

If you randomly replace parts without confirming they are defective, then you can wind up fighting yourself. For example, lets say that you have a bad _______ . And you replace the ignition control module in an attempt to fix the unknown issue. Now lets say that the new module is defective, or you don't plug it in correctly or what ever. How many other parts will you replace before re-replacing the ignition control module? So if you want to throw parts at it, try the new one and then put the old one back on and get a refund from Amazon for the new part. But the best advice is to find out what the problem is before replacing any parts at all. I knew a guy that spent over $1,200 replacing random parts without fixing the problem. All these new parts and it still would not run. And he refused to return that new parts that didn't fix the issue. So I suggested that he get it diagnosed by a local repair shop for $85. He said "I'm not wasting $85, are you crazy?!". In the end he gave up, so I volunteered to look at it for him, free of charge. Guess why his rig would not run, even though it had so many brand new parts ... The problem was that the fuel gauge was broken. The gauge was stuck at 1/2 when the tank was bone dry. I had to pull the pump out of the tank to find this out, but the pump went right back in, and with a couple gallons of gas in the tank, it ran great. So for the final repair: He said he normally has to fill the tank every 2 weeks at most because he only uses the rig to go to work and back and nothing else. Great, so I told him to fill the tank every 1 week and you will be fine, no fuel gauge needed. No need to spend any more money fixing the problem.