Hello all and thanks in advance for any help. I have a fuelling problem on my 88 f250 that I'm trying to diagnose. No fuel coming out of the high power pump (it's buzzing when I ground pin 6 of DLC, but nothing's coming). Disconnected power to the HP pump and unhooked fuel line from tank side of pump (between fuel tank selector valve and HP pump). Grounded pin 6 again to power LP pump and no fuel coming out of fuel tank selector valve. Unhooked supply lines on tank side of tank selector valve and tested both LP pumps by grounding pin 6, and both were supplying fuel in spec. My question is, should the LP pumps be pushing fuel all the way through the fuel selector valve when the high power pump is not hooked up? Or do the LP pumps only fill the reservoir in the valve and the HP pump pulls from that? I figure either the valve or the HP pump is tango uniform, but I'm not sure which ...

 

The selector valve is locked into a detent by the in-tank pump to the tank the that the in-tank pump is running in by about 6 PSI fuel pressure. There should not be any resistance to the fuel going through the valve and you should have about 6 PSI at the out put side of the valve.
When testing the valve with air pressure never use over 5 PSI air pressure.
There may a blockage inside the valve.

 

Thanks for the reply ... guess I'll need to make a trip to the pick n pull yard as I don't believe that valve is readily available.

 

I would not put much trust in one of these valve from a pick n pull yard as any time these valves go unused for and extended time period the "O" rings stick on the shafts and the return fuel will go to the front tank no matter what tank you are pumping from.

Most seem to be still getting the valves new on line and from special order from Ford dealers.

Info:
Ford E

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