I have a 91 f150 5.0 that I just bought and put a new gas tank and fuel pump on it. It will start and run perfect but when it reaches operating temp. and kill it, it will not start or try to start until engine has cooled and then it will start as soon as you hit the key. I've checked fuel pressure and relays, it's all good. I replaced the control module and have fire from the coil to distributor and plugs but will not start after warmed up but will run perfect all day until you kill it. Anyone have any ideas?

 

My '91 F-250 5.0 was doing the same thing, after looking things over well there were some bad ground cables, also the starter was showing age. After adding some heavy duty ground cables and replacing the starter i have not had the issue's again. Not sure 100% if it was either that caused the starting problem but it seems to have fixed it.

 

I should clarify that on my 91 f150 that when the engine is cold it starts and will run all day just perfect but when you kill it the engine will turn over but will not start until engine cools. The fuel system is operating properly and there is fire to the plugs. I did put a new coil on it thinking the fire was slightly week but there was no change. Thanks for any ideas you may have.

 

Yup, exactly the same issues i was having.