My 95 f-150 4x4 5.8l starts fine and runs fine when cold. Once it warms up for 5 or 10 minutes and I shut it down for 5 to 15 minutes it just cranks without firing up. I replaced the fuel filter no difference. Yesterday after filling the rear tank I realized that the filler neck and the tank are rusted through. Could this cause this starting condition?

 

Does it do anything strange if you let it run after being warmed up?

Did you test for fuel pressure when it wouldn't start up?

 

Did you check for spark when hot?

 

It continues to run fine until I shut it off for a while. I haven't checked for lack of spark as it eventually reluctantly starts after much cranking, (like off and on for 5 to 10 minutes). If my battery wasn't brand new I'd be DOA.

The question has me thinking in terms of gas cap issues and vacuum within the fuel system in relation to fuel starvation and flooding. Being that I don't smell gas (flooding) I'm thinking starvation. I don't really understand the fuel system enough to diagnose the problem. However I know that the cap is supposed to be on for some reason and a SEL will come on if you don't have a gas cap. I've had the light come on but being an OBD 1 no code is saved and is useless. Holes in the tank should be like a missing gas cap. I appreciate your thoughts.

If this is fuel pump related can I pin it down by switching to the other tank when it won't start?
I appreciate your thoughts.

 

Something you can try,
Get a spray can of carb and choke cleaner, when the vehicle refuses to start spray a 2 second shot of the carb cleaner into the air filter intake and see if the vehicle starts even momentarily until the shot is used up. If it does start for even a few seconds that would rule out the ign system and point in the direction of the fuel system. Let us know what results you received. (Don't like to use starting fluid because in the wrong amounts , it can cause engine damage whereas choke cleaner is just like extra gasoline)

 

Another thought just occured to me; could help, could not. You might try tapping the EEC power and fuel pump relays when its hot. They are the green and brown colored ones next to the underhood fuse box. In fact, check to see if the Pink/blk wire has power when cranking when its a no start.

 

When it refuses to start what do you hear when you turn the key on, you should hear the fuel pump run for the usual 1-2 seconds to prime the system, also what if anything do you hear if you remove the fuel cap when it refuses to start. If you hear a big rush of vacuum your starvation theory may be valid.