I'm helping a friend with a 87 F250 (460) with dual tanks figure out why he's not getting any gas to the engine. This truck is carbureted, and has an electric fuel pump in each tank (no mechanical pump.) I found a wiring diagram on this site (after much digging) and we have checked everything in the circuit except we can't find the fuel tank selector relay. This relay distributes power from the main fuel relay to whichever tank is selected. It is also the most convenient point to apply power directly to the fuel pumps, so we can check if they are working. It's not with the other relays (fuel pump and trailer wiring) in the relay box right behind the washer fluid reservoir.

We've checked everything else, and it seems to be working (oil pressure switch bypassed, fuel pump relay, inertial switch, fuel tank selector valve, fuel is in the tank, etc.) The truck runs fine if you manually dump fuel in the carb.

To sum it up - where is the fuel tank selector relay!

 

My understanding is that there is no relay. The selector switch decides which pump is energized.

 

Note that this thread is over 1 year old.