[SOLVED] Need Help with a 1997 GMC C1500 5.7 Crank but no Start

[MythicalRewards]

Hey guys, so I'm a little bit of a situation. I have a 1997 GMC Sierra C1500 with a vortec 350, and the truck won't start. It all started right after I got gas. I started the truck, drive to the gas station exit, and as soon as I give it gas, it inches forward a couple inches and shuts off. It didn't sputter out, just died as soon as I gave it gas, and it wouldn't start. The truck, when it did run, ran pretty smooth. The only issue it had was a hesitation when you went to give it gas. When I go to crank the motor, it will turn over like it usually does, and it sputters just a bit, like it wants to start. A couple of days ago, I check the fuel pressure, and when it was priming it was 65PSI. After the fuel pump shut off, it jumped down to 60PSI, and then from there, it would slowly drop to 40PSI, and that's where it would just stop. I've plugged off the return line, and of course the fuel pressure shot WAY up, but it still leaked down, so I don't think it's a bad check valve on the fuel pump. The truck has spark on every spark plug and I’ve unplugged the fuel pump relay, cycled out the lines, and then tried to run it off of starting fluid.

So far what I've done is, I've replaced the fuel injector assembly with the MFI spider assembly with a new fuel pressure regulator, I have replaced the timing chain, the crankshaft sprocket, and the camshaft sprocket, the ignition coil module, and the coil, and to no avail. I don't think it's a compression issue, because like I said before, the truck ran good, besides the hesitation on acceleration. I haven't had a chance to test the new fuel pressure after I replaced the fuel injectors, but I'm assuming it's fine now, because the truck is still acting the same as before.

The only thing I can think of is to replace the entire distributor, because I know these old vortec engines had issues with the distributors jumped teeth on the cam gear, and the reason why I think that is, whenever I spray starting fluid down the intake, it backfires right back at me pretty quickly if I give it a good spray. Another thing that's worth mentioning, is while cranking it, you can smell a hint of gas. I'm not sure if's coming from the exhaust or the front, but my guess is from the exhaust, and that's because if you shine a light up the tailpipe, you can see some very small amount of smoke. And that's what's throwing me off. The smoke smells just like gas, not oil or water, and again, it's a very small amount of very light, fumey smoke.

Sorry if this post is all over the place, I just got done replacing the fuel injector assembly and I'm pretty upset that it is still not working. I would just like to get this fixed so I can focus solely on college. Any pointers or help would much appreciated!

 

[Ron88]

It may have jumped time. That may make it back fire through the intake.

 

[Erik the Awful]

You can replace the distributor gear without replacing the whole distributor, and it's a lot cheaper. Have you put a timing light on it? That's even easier than pulling the distributor. Diagnose before you load up the parts cannon.

 

[MythicalRewards]

It may have jumped time. That may make it back fire through the intake.

That's what I was thinking, but I've threw too many parts at with the initial diagnoses.

You can replace the distributor gear without replacing the whole distributor, and it's a lot cheaper. Have you put a timing light on it? That's even easier than pulling the distributor. Diagnose before you load up the parts cannon.

I haven't tried that, because I was under the impression that timing lights were expensive, but I see Harbor Freight has one for like $35 USD. Is there anything special with this truck when it comes to checking ignition timing, because I've heard the ECM will advance and retard the timing a bit, or is it just like old motors back in the day?

 

[Ron88]

If I remember this right if you line up the line on the crankshaft damper to the 0 degree mark your rotor should be pointing to number 1 the only other place it could be is at 6 which means you need another full turn back to line up the line on the damper with the zero mark and then it should be at 1 , oh yeah you have to remove the cap to see. Its been awhile but that's how I remember it.

 

[MythicalRewards]

So I hooked up the timing gun to every spark plug wire, cranked the motor, and only cylinder three is firing correctly. Cylinder three's signal fired rapidly on the gun. The timing gun didn't receive any other signal on that bank. However, on the other bank, the gun picked up signals on spark plugs eight and six, but these signals were very scarce; the gun went off once or twice, and then it stay off for a second or two, and then flash like couple times and repeat.

When I said I check all of the spark plugs, I meant I grabbed a spark plug from an LS spark plug job I did for a friend, removed the spark plug cable from the engine, plugged that spare plug into the boot, grounded it to the battery, and then cranked the motor, and the plug fired. However, when I did that to cylinder one after my timing gun test, In hooked the timing gun to that spare plug and boot, and it received signal just like cylinders eight and six. I'm thrown in a little bit of a loop right now, anyone have any suggestions from here? I know plugs are different between engines when it comes to gap and their materials, so I know I might be looking into the spare plug test too much. What I think, is the distributor is producing weak spark due to the contact points. I haven't had much time to take a look at the underneath of the cap, so I can't say for sure if has weak spark or not.

Again, any pointers would very much be appreciated!

 

[MythicalRewards]

I haven't pulled any of the plugs yet, but I doubt every single spark plug went out all at the same time when I was pulling out of that gas station, but I will update you guys once I get a couple of the old plugs removed.

 

[east302]

After the fuel pump shut off, it jumped down to 60PSI, and then from there, it would slowly drop to 40PSI, and that's where it would just stop. I've plugged off the return line, and of course the fuel pressure shot WAY up, but it still leaked down, so I don't think it's a bad check valve on the fuel pump.

Isn’t the check valve on the suction side of the pump to hold prime?

Say you pulled the fuel filter and put a ball or needle valve in its place, pressurized it and then closed the valve.

If the pressure dropped at the schrader valve downstream of the filter then you’d know it was either the regulator (leaking back into the return) or an injector leaking since it was isolated upstream.

If it held pressure at the test port, then the loss would be between the filter (closed valve) and the pump relieving pressure back into the tank.

According to my wife, I’m wrong quite a bit but I did stay at a Holiday Inn a few years ago. It might be worth looking into testing it that way.

 

[MythicalRewards]

Isn’t the check valve on the suction side of the pump to hold prime?

Say you pulled the fuel filter and put a ball or needle valve in its place, pressurized it and then closed the valve.

If the pressure dropped at the schrader valve downstream of the filter then you’d know it was either the regulator (leaking back into the return) or an injector leaking since it was isolated upstream.

If it held pressure at the test port, then the loss would be between the filter (closed valve) and the pump relieving pressure back into the tank.

According to my wife, I’m wrong quite a bit but I did stay at a Holiday Inn a few years ago. It might be worth looking into testing it that way.

I'm not if it works like that, I was told to plug the check valve off, and if it's still leaking, then it's either fuel reg., fuel injectors, or fuel injectors IF prime is good.

I do have an update for y'all. I took out the cylinder one spark plug, and it was covered in gas, so I cleaned it off and dried it. I then put the boot over said plug, grounded it to the battery, and it sparked and the timing gun got signal from it. So I reinstalled it to the engine, and tried again, and unfortunately, it didn't receive a signal. After that, I wanted to see if the timing light would receive signal if I swapped the boots on the spark with cylinders one and three. So I did just that, I swapped the boots over, but I left the boots at the distributor, so the distributor was sending cylinder's three spark to cylinder one. I know this out of time, but I wanted to see if cylinder one would finally give me a reading, and it did! So I then swapped the boots at the distributor so the ignition timing will be in order, so essentially, I just swapped over the spark plugs wires from three and one, and lord behold, cylinder three was giving its reading again, and cylinder one stopped giving a reading.

I have attached a picture of cylinder's one spark plug after I removed it to this post. I'm thinking at this point, it might be a bad distributor cap, rotor, or maybe the whole darn thing. I know spark plugs have a better spark when they're outside of the bore due to atmospheric pressure. I'm still a little lost, so if anyone has an idea, please do reach out! I appreciate any and all feedback!

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[HotWheelsBurban]

I think I have read on here that the Vortec distributor cap, because of the way it's made to fit back there in the small space available, is prone to misfire or crossfire on the #1 and #3 cylinders. You might just have a bad cap, or it could be carbon tracking inside. That will give a similar result. The GM electronic ignition coil is putting out around 40KV(40,000 volts) so all that zap will take the easiest path.
I have the United Motor Products blue vented distributor cap on my Burb, and I'm very happy with it. In Houston, Texas we have a LOT of humidity, so the vent is a good thing. The distributor housing is supposed to have vents in it, but I haven't stood on my head to see if it does on my truck.
UMP has a cap and rotor kit that Rock Auto sells, but I had a Blue Streak rotor with brass contacts, so I used it. I get 2 years out of them, and only 6 months out of the regular grade white rotors.