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A bad Idle Air Control will keep the car from idling, like Kevova said you can try the pressing the fuel pedal to identify the problem as the IAC. I was able to get the car running when I had problems with the IAC (wrong tip) by doing exactly what he was saying. This pointed me that direction and solved my problem.
Is the engine doing everything else like priming still? Does the fuel system maintain pressure?
One piece of advice, be sure to match the tips of the Idle Air Control Valves. They have different styles and shapes so you have to get the exact match to what your car came with. I learned this the hard way....
This Corvette Forum is the greatest thing for Corvette Owners and enthusiasts! One thing helps us help you is to have as much information about the car in question as possible. It would be great if you posted the details of your car in your profile page. That way we can find answers easier and help you faster which helps everybody involved.
In a quiet environment, turn the key to RUN, but don't crank it.
>>> Did fuel pump run for a few seconds then stop? (If = NO, you have ECM is not powering up, or fuel pump circuit or pump issues).
If = Yes:
With key still ON, pump stopped, turn key BRIEFLY to START, then back to RUN. Listen for fuel pump.
>>> Did pump run again for a few seconds and stop?
If = YES, you have a fueling or secondary ignition system problem.
If = NO, the distributor is not producing reference pulses. This is almost ALWAYS the internal coil in the base, inside, the distributor. About a $30 part, and requires distributor removal and disassembly to renew.
I've replaced dozens of these coils in GM HEI and EST distributors over the past 30 years for intermittent no-starts. I use the above test for diagnosis. Takes less than a minute, and no tools to conduct. Very reliable for the pick-up coil. As an aside, I have NEVER changed an ignition module and rectified this "no pulses" problem. In my experience the modules do not fail. The pick-up coils do.
Meaning the ignition coil that usually is the probelm?
NOT AT ALL. Ignition coils are part of the SECONDARY ignition system. (I make specific reference to the secondary side if the result of the "quick crank" is YES.) Pick-up coils have two little wires one white, one green, with a natural colored
two-cavity connector that connects to the module.
Another aspect of "no reference pulses is that there will also be "no spark" either.
The "ignition coil" in an 85 distributor is mounted in the cap. I've never replaced one. They don't fail either.
If I recall correctly, you had another thread on your "no start" and the reason at the time was "no spark". If this was you, and you did not replace the "pick-up" coil at that time, you should this time, and you're intermittent no-start should be cured. If this wasn't you, I apologize for my confusion.
I want to look into this. Do you know how I can test the pick-up coil? And thanks for the information, I’m glad I’m learning a lot !
