Hello,

Purchased an awesome 94' Z28 back in June, it was bought from a friend who needed a car with better economy and who absolutely couldn't work on it.

It was running before the water pump went out, and I bought it knowing the new water pump had been haphazardly installed and was still leaking, the car at this point would not run. But interior and body were in great shape and i knew the engine not running wasn't catastrophic.

I finally figured out the leaking water pump shorted out the Opti-spark, ignition module and the coil. After changing them and fixing the leaking water pump problem the car would finally crank however it takes like 16 to 20 seconds for it to actually fire off. It's been this way for a while now with no change. The only time it will immediately re-fire is if I kill it dumping the clutch otherwise, anytime longer then say 3 minutes of ignition off it takes 20 seconds of cranking before it fires. If it's the 1st crank is several hours it starts and idles fine. If it sets only for a short time, it takes 20 seconds of cranking then fires, but idles at 2k for 30 seconds or more then idles down.

I took it to a local guy here in Panama City (only one in town I could find who could actually pull codes) and he told me it was possibly my security system. Told me to go get a security by-pass and install it since apparently a previous owner had already by-passed it with a home made resistor and wire. He also told me there were 3 codes before resetting the computer, after the reset the only code that came back was 36 "detects too many low resolution distributor pulses or not enough high resolution distributor pulses". I left and purchased a Vats Bypass Module at a local Lock and Key store, installed it and still have the exact same issues.

Obviously either ignition or fuel delivery is being cut by the computer and after cranking for some time it gets turned back on fires and away I go. So the question I pose today is do I need to back into the opti-spark? The disc inside with the windows, I know I made sure it was clean, and I am pretty sure it was installed correctly. Is it possible to install the disc wrong? Would it even run if it was? Am I seeing the result of this being installed wrong? Or do I need to look else where?

Is there any testing advise you could provide that would single out the culprit?

Any help would be appreciated. Thanks.

 

It is either the fuel pressure regulator and/or the tfuel pump check valve. Check valve cant be seviced. will need to replace the pump. the regulator may be a good cheaper first step. if that doesnt fix it put a pump in it. Or you could cycle the key on a few times then turn it to crank it should start no problem is my hunches are right. if i am right, the regulator can allow the fuel pressure to bleed back into the tank after sitting. same with the fuel pump check valve. only if it had a return fuel line you could block that off and confirm wich one it was. let us know what happens. Hope i helped in some way.

 

Try checking for fuel pressure first. If you have one, plug the fuel pressure gauge on the end of the fuel rail with enough of a hose extension so that you can see it from inside the car if doing the diagnosis yourself. Turn the key to on and listen for the fuel pump prime. Watch the gauge and if it moves up and then slowly starts to drop then you have an issue with the fuel pump check valve. If that's the case, you will need the whole sending unit because as far as I know, you can't get just the valve.

If the pressure doesn't rise and there is no pump prime from a cold ignition key on then it very well could be the vats not allowing the fuel pump signal to engage.

Start with the easy things first. Good luck and post your findings when you get a chance.