I have a 1991 GMC 4x2 sierra pick up. When the engine is cold it will start, but once it reaches temp it shuts down. I have replaced the brain and battery already and have checked the fuel pump and lines and they are sound. The coil has 12v going to it but it is not sparking. There is fuel at the rails but not in the injectors. If anyone knows what could be causing this problem please respond. Ty

 

Do you have a check engine light on?

 

yes and it is not on

 

A bad coolant temperature switch can cause that. I had one leave me stranded on a trip home once. It started sputtering like it was running out of gas and then finally died. By the time my father got to me with our car trailer it started right up and we were able to drive it on the trailer. This was about 5 hours later. Sounds like a similar situation as yours.

 

great thanks man, ill go have a look

 

ok there is a switch on the manifold for the gauge and that is not it and one on the head that is the knock sensor. I looked to see if the coil was sending spark to the plugs and it is not, but the power is there. There is fuel pressure to the rails but the TBI is not sending a pulse of fuel.

 

The one on the manifold by the thermostat is the engine coolant temp sensor. Thats is the one I had to change. These would throw a code though. When you first turn your key on does the service engine light come on and then turn off after a few seconds? Did you replace the ecm trying to fix this issue and it is doing the same thing with the new one? That is the only thing that I can think of that would kill both the spark and the injector pulse.