Well, I just bought a 90 Cavalier 3.1 V6 strictly to sell and make profit off of. Anyways, I put in a new fuel pump and 3 injectors because they were bad. Started up the car right away. The car ran okay. A little hesitation problem once in a while but I think it's unrelated. I drove it around for a while and stopped for lunch. Came back out 20-25 minutes later, and the car won't start. It cranks and cranks, but will not fire. It is getting fuel up to the injectors. Called a friend to get a ride. Came back an hour later and it fired right up. It seems like it will only start when it is cooled off. What could be causing this? I am lost. ANY help would be greatly appreciated. Thanks in advance.

 

First, isolate the problem. You said you have fuel, what about spark? Get a spark tester and see. May be a coil, ground, anything. See what part of combustion you're lacking, then investigate. Check coil, wires, grounds...you'll find your problem. Really need more info to be able to say where exactly to look.

 

From working at a parts store I will tell you the genera result of a car only starting when its cold. A bad starter. The starter has to work harder to start a warm engine because there is oil pressure in the engine and everything is heated up causing more friction because things are close together. Not saying this is always true, but take the starter to have it tested and see how many amps its drawing, your electrical system can only give it so much, and when its hot from engine heat it needs more to do the same work anyway, also when the battery is warm it has less to give. It might just not be turning the ingine fast enough.
Or like mentioned above, it might be the coil, becaue it is heat sensitive to. Another thing is the ignition control module, becasue they will fail do to heat also. Good luck. All these can be tested.