I have '92 Ford F-150 four wheel drive that will not start on the first try after the engine is warm. The truck starts great when the engine is cold but when it is warm you can turn to start the engine, it cranks but will not start. You can turn the key to the off position and then back to start and then it will start up. I have installed a new pressure regulator. I can put a fuel pressure gauge on it while running and it shows 39 psi, but when you cut the engine off the pressure immediately drops to 0 psi. I've been told there is a check valve or check ball in the fuel pump module. Is this true and does anyone have an idea if this could be my problem. Truck runs great otherwise. Thanks.

 

Try to test the fuel system to see if the fuel pressure is bypassing the pressure regulator or the fuel pump. The way to test it, put the pressure guage on the fuel rail, start up the vehicle, then crimp the "rubber fuel return line", (DON'T CRIMP A PLASTIC LINE, IT'LL CRACK AND LEAK)to check the max pump output. Then shut off the vehicle and crimp the "rubber return line" the pressure should stay up if the fuel pump check valve is ok. If the pressure drops when you release the crimp on the return line hose, pressure regulator valve bad. I have seen many pressure regulators go bad, even new ones.

 

I have a similar problem on my 95' explorer, except mine is intermitent and infrequent. Mine will start but won't idle unless I give it the gas, otherwise it will stall. Like yours, it only happens when the engine is warm. I can drive it away and the idle problem goes away after a minute or so.
But like yours, I found that if, instead of trying to restart it, if I turn the key to the fully off position, it will start fine.

On your's, I don't see this as a mechanical problem, as you mentioned that the engine starts fine if you turn the key to the off position before trying to restart it. So, I suspect that we both have an electrical problem. Anyone have any suggestions?

 

I had a 95 F-150 with a similar problem so I got some books from the library and found a loose wire coming from a module on the drivers side fender. The wire controlled a sensor for fuel mixture. Hope this helps. Also you could try a code scanner, they don't cost alot.