First off, looonnnggg time lurker, first time poster.

I'm helping a friend with his 1996 F150 XL with a 4.9L and 5spd. The problem is that on first start up, its fires right up and runs great. If you shut it off after say, 30 seconds, won't restart. Its not a fuel issue as it does this no matter which tank (Dual tanks), has almost 60psi fuel running and key off holds 50+psi over night and will NOT start when using starting fluid. Pulled a wire, ground the spark plug and has spark (possibly weak). Still no start. if you let it sit for 30 seconds or so, it'll start but blow smoke likes its really rich. It coughs and sputters for a second then clears out and runs great. He has replaced Coil, Coil harness, ignition module, a new distributor (not a rebuild), starter, starter relay and ignition switch. No difference. When it starts, it runs like a dream. Kind of looking at where to go from here. I would rather troubleshoot then be a parts changer. Trying to help save him some money instead of paying a shop. Any help is appreciated.

 

Check the engine temperature sensor, it was disconnected on my '96 and it was hard to start hot. Also, pull computer codes.

 

Might be a long shot but something else to check would be battery connections and/or grounds. I have the same exact truck and I used to run into a hot start no start condition. Happened a lot when I stalled the truck (I learned to drive manual on this vehicle). Not quite the symptoms you've described but it doesn't hurt to check them out. It could be that the connections need cleaning/replacing.

 

sound like temp sensor, my sisters jeep did the same thing along with a 80s f150 my friend had. those symptoms are usually universal among engines.

 

It may only be running for 10 seconds and I shut it off and it will be really difficult to restart. Does this sound like it can still be a temp sensor?

 

I have bought the truck from him as he was done dealing with it. I got it home and pulled codes and none. After the distributor and the ignition module were replaced and driving it around, it threw a code. Temp sensor. Replaced it and all is well. Thank you all for the help.