98 K1500 Z71 Ext Cab 5.7 Vortec - No Start

[stutaeng]

Yeah, I'm pretty sure my other truck (2000 K3500) with the 5.7 also has around 55 psi fuel pressure with key on engine off. I chased a lean condition on that one for a while, but even with stock spiders it started just fine. It turned out to be a dead injector causing the lean condition, so I bought a new MPFI set. I can double check tomorrow, but certain it still has that same fuel pressure.

But the fact that it starts briefly with carb cleaner is perplexing...

My 4.3 had a crank but no start that I was never able to solve. It did it under wet/damp conditions only...I think it had to with the spark in the cap not jumping correctly to metal tabs. It seemed like I had spark, and obviously fuel.

 

[jd1794h]

A picture of my plug tester is attached.

And to be honest I only checked cylinder number 1 but since she runs great for a few seconds on carb cleaner, she must be getting spark to all the cylinders and at the correct time or I wouldn't think she would start at all.

Also did a tune up a few months back, with new plugs, plug wires, distributor cap, rotor, ignition control module, and ignition coil so spark shouldn't be an issue.

 

[stutaeng]

I bought one of those, but I read you can't tell how strong the spark can jump across.

There's another style where the little electrode can be screwed in or out, and you can actually see the color of the spark as well. I think the auto parts store should have them. I eventually had to buy one of these other ones.

Maybe @Schurkey can chime in on this one. He's top notch with diagnostics...

 

[kennythewelder]

A picture of my plug tester is attached.

And to be honest I only checked cylinder number 1 but since she runs great for a few seconds on carb cleaner, she must be getting spark to all the cylinders and at the correct time or I wouldn't think she would start at all.

Your pic doesn't show. You have to drop the http. It's been an issue here for a while, but I looked it up and see what your using. What you are describing by saying it runs on carb cleaner, is a sign of low fuel. Then you say your plugs are wet. That is a sign of no spark, or a fuel system that is dumping fuel into the manifold. Them you say it runs grate on carb cleaner but when it burns that off it quits running
Again no fuel. The only other thing that causes that issue is passlock, but I think passlock shuts off fuel, when it's activated, if I remember rite. You can verify that engine bhas not jumped time by lining up on #1 TDC on the compression stroke, the removing the distributor cap, and checking that the rotor is pointing at #1 plug wire, on the distributor cap, but again you say it's running good until it shuts off. Again passlock. But again no because you say you have fuel. Plugs are wet. I'm sure I could figure it out my self if I was there,but all I have to go one is what you tell me.

 

[kennythewelder]

Ok, I see you fixed the pic before I posted my reply.

 

[jd1794h]

Ok, I see you fixed the pic before I posted

Your pic doesn't show. You have to drop the http. It's been an issue here for a while, but I looked it up and see what your using. What you are describing by saying it runs on carb cleaner, is a sign of low fuel. Then you say your plugs are wet. That is a sign of no spark, or a fuel system that is dumping fuel into the manifold. Them you say it runs grate on carb cleaner but when it burns that off it quits running
Again no fuel. The only other thing that causes that issue is passlock, but I think passlock shuts off fuel, when it's activated, if I remember rite. You can verify that engine bhas not jumped time by lining up on #1 TDC on the compression stroke, the removing the distributor cap, and checking that the rotor is pointing at #1 plug wire, on the distributor cap, but again you say it's running good until it shuts off. Again passlock. But again no because you say you have fuel. Plugs are wet. I'm sure I could figure it out my self if I was there,but all I have to go one is what you tell me.

I know man, it is utterly confusing. I'm thinking it is flooding out. That's the only thing that makes sense in my head with wet plugs. She starts on the carb cleaner and when the injector assembly tries to take over it just dumps fuel which floods it out. Which is why I'm thinking the injector assembly may have just been bad right out of the box.

As for passlock, the security light behaves as it should. Maybe that isn't enough but I would think the light would be on if that was the issue.

 

[HotWheelsBurban]

I know man, it is utterly confusing. I'm thinking it is flooding out. That's the only thing that makes sense in my head with wet plugs. She starts on the carb cleaner and when the injector assembly tries to take over it just dumps fuel which floods it out. Which is why I'm thinking the injector assembly may have just been bad right out of the box.

As for passlock, the security light behaves as it should. Maybe that isn't enough but I would think the light would be on if that was the issue.

Passlock will allow you to crank, but the fuel pump relay gets shut off after 2 seconds. So it will not run longer than that. This is the issue that got me to this forum!
I think the security light is supposed to go off after the truck starts and stays running. My Burb has had passlock deleted in the PCM, so that light stays on. That doesn't bother me at all, as long as it starts!
These trucks are old enough now that the soldered connections in the passlock box are coming loose, just like the radios and wiper motors do. So they'll start acting crazy and then not work at all.
That said, it sounds like you have more of a fuel flooding issue. Injection unit, fuel pressure regulator, idle air control valve, throttle position sensor, mass air flow sensor, in order to check. Good luck and let us know what it ends up being.

 

[jd1794h]

Passlock will allow you to crank, but the fuel pump relay gets shut off after 2 seconds. So it will not run longer than that. This is the issue that got me to this forum!
I think the security light is supposed to go off after the truck starts and stays running. My Burb has had passlock deleted in the PCM, so that light stays on. That doesn't bother me at all, as long as it starts!
These trucks are old enough now that the soldered connections in the passlock box are coming loose, just like the radios and wiper motors do. So they'll start acting crazy and then not work at all.
That said, it sounds like you have more of a fuel flooding issue. Injection unit, fuel pressure regulator, idle air control valve, throttle position sensor, mass air flow sensor, in order to check. Good luck and let us know what it ends up being.

Running down your list real quick:

Injector assembly - replaced with re-manufactured unit
Fuel Pressure regulator - one came with the re-manufacured Injector assembly
Idle air control valve - replaced
Throttle position sensor - replaced and values verified with scanner
Mass airflow sensor - replaced a few months ago during round 1 with this truck. Also unplugged the MAF (should force computer to pre-programmed air to fuel ratio) and cranked but still no start.

I suppose it could be some wonky electrical issue with passlock but I am still more suspicious of the re-manufactured Injector assembly.

Whatever it ends up being, I will definitely let you all know. And thank you all for your help so far. I really do appreciate it.

 

[Erik the Awful]

Timing too far retarded?

 

[jd1794h]

Timing too far retarded?

I suppose something could be causing the computer to throw the ignition timing off but wouldn't the timing have to be really far off to cause a no start? My scanner is not advanced enough to check the computer for ignition timing.