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Yes that’s the IAC passage - at key off the pintle should extend out far enough for you to see the point before retracting to its set position.
Originally Posted by Chevy frustrating me
2)I tested with a spark plug tester that flashes good while I crank.
What I mean is did you test for spark directly from the coil (with the coil disconnected from the distributor cap) or did you test for spark at the end of one of the spark plug wires? Having spark directly at the coil but not at the end of one of the plug wires indicates problems inside the distributor cap because the spark isn’t passing through the ignition rotor to the plugs. Possible reasons are corrosion, bent contacts on the rotor, faulty cap/rotor, loose plug wire connections, or the rotor not turning at all because the timing chain is broken.
The spark tester is at the end of spark plug wire at spark plug. When I rolled the engine over to tdc the rotor would point directly at #1 cylinder last time I checked.
Last edited by Chevy frustrating me; Apr 13, 2021 at 11:07 PM.
Sorry I missed this earlier but don’t test the IAC for movement if it’s not installed in the TB. If it extends, the pintle will thread all the way out of the housing without anything to restrain it.
Have you done any fuel pressure or volume testing?
I haven't done any fuel pressure tests but I have tried putting fuel down tbi with no start. It is exactly like others who have a faulty iac just rolls over and over like no compression.
I ordered a new iac connector and its probably just wasting more money but idk what to do. I am also going to get a compression tester today.
I don’t think you’re wasting money on a new connector - since the test light showed the control circuits are functional, it’s certainly possible the connector is to blame.
Also, since it initiated the IAC before, maybe try unplugging the ECT again?
I’d recommend vacuum testing before compression testing for the simple reason that vacuum testing is faster, at least for determining whether or not base mechanical problems need to be further investigated. Vacuum and compression are directly related in that they both depend on the engine’s ability to move air. If the vacuum reading is steady and there’s no needle fluctuations, there’s no mechanical problems affecting compression or valve timing and compression testing isn’t necessary. If it’s not steady, or if it’s low or not present at all, there’s a base mechanical problem.
A couple of quick tests to determine if fuel pressure is an issue:
1) Try starter fluid. Use it sparingly, in short bursts during cranking, directly into the TB or through one of the vacuum ports. Don’t try to keep it running on starter fluid alone - if the engine starts at all, immediately stop spraying it.
2) Pinch off the return line to the fuel tank. Under the cab near the firewall, the fuel lines change to rubber or nylon as they transition from the frame rail to the engine. Hose pinching pliers are ideal or at least something without a sharp edge. You can also disconnect the return line and plug it. This will dead head the fuel pump and max out the pressure.
If the engine starts with either of these tests, further fuel pressure testing is required.
The connector didn't work still no iac movement and no start. No vacum when I crank the engine over when I plug the mighty vac like the picture. When I pump vac myself it will hold 17 steady. Not sure if I should be plugged in somewhere else.
The first place you tried to measure vacuum was the MAP sensor port - it should’ve had full manifold vacuum on it.
The brake booster line should also have full manifold vacuum.
It’s possible unknown blockages or the engine hoses are leaking and preventing accurate vacuum testing, So here’s what I see as your choices at this point:
1) Try one more time to check for cranking vacuum on the PCV return port - it should also have direct manifold vacuum. Don’t tee into the line, just hook your gauge hose directly to the port.
2) Try holding your hand(s) over the TB barrels as a helper cranks the engine and see if you can feel vacuum against your hand.
3) Proceed with compression testing.
4) Try dropping the exhaust to check for restrictions. If you decide to drop the exhaust, I’d recommend just pulling the pipe off the manifolds - then you can crank it and see if it starts, even if it’s only a quick fire before it dies.
