I have a 91 f150 that after running for a bit and it getting hot does not want to start. i have to let it cool down for like 30 minutes before i can get it to start. When I take off the gas cap there is a big release of gas vapors. any clues as to what it might be or how to fix this? also the oil pressure drops when hot as well.

 

Welcome to FTE.

What *does* happen when it won't start?

Does the engine crank when you turn the key? Or no?

The oil pressure dropping on a warmed-up engine is an indication that it's worn out.

The vapor noise, something is up with your EVAP system - Evaporative Recovery.

 

the fuel pump seems to not work and maybee i have vapor lock not sure

 

Best thing to do first, is see if there are any stored codes. Your problem could just as easy be electrical vs fuel related. These older trucks are known to suffer such problems, so pull the codes first, and see what you got there. Here is a how to
Ford Fuel Injection » How To Run a Self-Test

 

yes the engine cranks but does not ignite
i pull out the fuel pump relays and cool them off and then it will start but the engine itself does not overheat

an indication of what when the oil pressure drops??

any ideas for the EVAP system?

 

When you cycle the key on, can you hear the fuel pump run to prime the rail?