Engine Performance problem
1989 Ford F-450 V8 Two Wheel Drive Automatic 150, 00 miles
I have a 1989 school bus with a F-450 engine. We have converted it to a tail gating rig. It starts up perfect everytime and works great when going short distances 5 miles or less. When it gets hot, it starts to stall out and gets very hard to start. I took it to one shop and they upsized the starting coil as it was getting extremely hot. This didn't do the trick as I keep experiencing the same issue.
If it feels like someone reached over and turned off the key and it fires back up right away it's the injection pump.
If the same thing happens but it has to cool down before restarting it's the PMD / FSD(pump mounted driver).
If it stumbles and than stalls then it is air in the fuel lines. If it is this one try switching fuel tanks and just turn the key to run but don't start the engine. Listen to the fuel pump for a change of noise pitch. The pump is really loud when the pump is out of fuel and will have a muffled sound when pulling fuel. Sometimes the baffle in the main tank will brake away from the tank and the pump will suck air when the tank is just off full.
Also check for vacuum lock. If the fuel tank vent is plugged air can't get into the tank to replace the fuel that's drawn out. Remove your fuel cap and see if the truck runs.