Crank no start 1988 Chevy C1500 5.7 350 tbi

[PlayingWithTBI]

The line used to connect to a smog pump that I took off the truck,

That big port is supposed to go to the PCV valve. The one on the left goes to the EGR and the A.I.R. (smog) pump. On ones that do have the pump the vacuum line splits into 2 separate ones. The one on the right goes to the Charcoal Canister. They all have to be hooked up or, at least, capped off.

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[Slade88]

That big port is supposed to go to the PCV valve. The one on the left goes to the EGR and the A.I.R. (smog) pump. On ones that do have the pump the vacuum line splits into 2 separate ones. The one on the right goes to the Charcoal Canister. They all have to be hooked up or, at least, capped off.

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Capped off the line and all my other lines are connected properly. I set my engine to top dead center and put on the distributor cap to where the contact on the rotor was facing where the number one spark plug wire connects to the cap. Cranked over the engine with the same problem, it wants to start and will for a couple seconds then shuts off. I also noticed when I turn my engine over by hand with a breaker bar I don’t hear the hissing sound that I used to, could that be a problem? Could that be the problem stopping my engine from running? I still think this is timing related but last time I put on my cap by eye at tdc my engine started right up and stayed running, don’t know why it wouldn’t this time. Starting to get very concerned.

 

[Schurkey]

I set my engine to top dead center and put on the distributor cap to where the contact on the rotor was facing where the number one spark plug wire connects to the cap.

TDC-Compression, or TDC-Exhaust? Have you checked for compression on #1 when finding TDC?

If the engine RUNS, even for a couple of seconds, you got the correct TDC. But if it's just backfiring and sputtering as the crankshaft coasts to a stop, you might want to verify.

What happens if you turn the entire distributor about fifteen degrees counter-clockwise?

 

[Slade88]

TDC-Compression, or TDC-Exhaust? Have you checked for compression on #1 when finding TDC?

If the engine RUNS, even for a couple of seconds, you got the correct TDC. But if it's just backfiring and sputtering as the crankshaft coasts to a stop, you might want to verify.

What happens if you turn the entire distributor about fifteen degrees counter-clockwise?

Advanced the timing a couple degrees and we got it running, but it only runs when the throttle is partly open, sounds smooth but it won’t idle with my foot off the gas, why could this be happening? It runs consistently when my foot is on the gas though so we are making progress

 

[PlayingWithTBI]

sounds smooth but it won’t idle with my foot off the gas, why could this be happening?

You need to put it on a scanner and see what's going on with your IAC, that controls your idle. You may have other vacuum leaks too.

 

[Slade88]

You need to put it on a scanner and see what's going on with your IAC, that controls your idle. You may have other vacuum leaks too.

I have no vacuum leaks and I replaced the IAC valve a couple years ago, this must be a computer problem/timing problem, it must not be complete in time yet, I have everything plugged in, I do not have a scanner unfortunately

 

[evilunclegrimace]

I have no vacuum leaks and I replaced the IAC valve a couple years ago, this must be a computer problem/timing problem, it must not be complete in time yet, I have everything plugged in, I do not have a scanner unfortunately

If the engine will not run you do not know if you have a vacuum leak.

 

[smdk2500]

Are you setting your timing with the EST wire unplugged? If not that could be why you having issues.

 

[Schurkey]

I do not have a scanner unfortunately

Trying to fix a computer-controlled vehicle without access to a scan tool is madness; and about two steps from hopeless.

 

[Slade88]

If the engine will not run you do not know if you have a vacuum leak.

It will run