It could be a fuel related problem, however that wouldn't explain the sensitivity to heat. A bad fuel injector would exhibit itself more while driving than in failing to start. A bad fuel pressure regulator might cause the vehicle to have a longer cranking time before it starts, as will a weak fuel pump.
I tend to lean more towards a weakening sensor.
Oh, and me being stupid! I didn't even ask what engine you have.
Tuesday, June 12th, 2007 AT 12:50 AM