1989 Ford F350 460 engine stalls

Good day,

I have a 1989 F-Super Duty with 460 fuel enjected engine. When I start the engine after sitting several houre, the engine will run for about 15-20 seconds (fairly well) and then stall out. If I try to restart the engine, it will not restart. If I start the engine after waiting several hours the engine will start, but when I press the pedal the engine will quit.

I have replaced the spark plugs, rotor, fuel pressure regulator and oil.

The truck has two gas tanks. My son took a guage to the fuel line on the rails off the primary tank and determined the fuel pressure coming from the fuel pump was about 10psi and according to what we were told should be 40 psi. The secondary tank was not tested because it had not fuel.

I later filled the second tank with about 5 gallones of fuel, but it still would not start.

It does not matter whether I am running off of the primary or secondary fuel tank, it will stall after about 15-20 seconds.

Thank you,

Rick.