I have a 1989 Vette - I had the radiator flushed today and had a new catalytic converter installed. When I got the car home, I turned off the engine for a few minutes. I tried to restart the engine - It would not start - Only Cranks. I waited 1 hour and tried again - It started right up. I let the car run for a few minutes, turned it off and tried to restart. It would only crank. Any ideas??

 

When it won't start, that is the time to do some diagnosis to find out why. Automobile engines require spark, spark at the right time, strong spark, fuel and air and in the correct ratio, and compression in order to start and run. Use your timing light to see if you have spark and at the right time during cranking. Pull a plug wire and bring a grounded wire close to the plug wire, it should have a nice snappy, at least 1/2" spark. Connect a fuel pressure guage on the shraeder valve on the right fuel rail and turn the ign to run. You should have 35-42 psi of pressure and it should hold for a long time with the ign off. Rapid pressure drop indicates leaky injectors or a defective check valve in the fuel pressure regulator. Connect a noid light on an unplugged injector plug, or make one with an LED (light emitting diode) and a series 680 ohm resistor and crank the engine. You should see pulsing showing the injectors are being exercised. The homemade light must be connected with the correct polarity to work. Measure compression.
Another test is to spray starting fluid into the MAF and if the engine starts and runs momentarily, you aren't getting fuel sprayed into the intake.
If you have no or very weak spark, one common failure is the spark control module in the distributor when it gets hot, but works cold. Happened to my 87.