I had posted before about my 1990 E 350 7.5l gas van and its duel tank problem. With the fuel tank switch selected for the front tank, and with the front (midship) in-tank pump operating properly (the fuel pump and sending unit are brand new), the fuel is only drawn from the rear tank. The front fuel tank always has a full tank with all gas coming from the rear. Both sending units are giving accurate readings. At the gas station, the front tank is always full and the rear accurately shows its low fuel content.

Thanks to Partsguy Ed, I have replaced the Fuel Tank Selector Valve AND the Fuel Tank Toggle Switch.

I still have the problem! What the heck is going on here? The new Fuel tank selector valve did eliminate sudden and random stalling while using the front tank, though why oh why (and how?) does the front in-tank fuel pump draw fuel from the rear tank only?

How do I get the midship pump to use only the gas in the midship tank?

That weird cylinder type filter that sits on top of the midship tank broke during repairs, but my mechanic (an excellent mechanic) assures me that this part has nothing to do with the problem, but he's not sure exactly what's going on either.

Can anyone help with this dilemma? I thought for sure the FTSV and Toggle switch would solve the problem (in addition to a new midship fuel pump and sender unit).

Thanks

 

Sounds like the front fuel tanks pump is not pumping or the pressure (6-11 PSI) from the front tank is not reaching the selector valve.

Remove the pressure fuel line from the front tank at the fuel selector valve.
Point it into a bucket, have someone turn the key on and off a few times and see if fuel comes out of the fuel line.

 

Hello subford,

First, thanks for responding.

I called my mobile mechanic today, and he is coming over tomorrow. Both you and Ed have suggested that its the brand new in-tank pump he just installed in the front gas tank. So, he is going to test it out. He's trying to think of a way to test it electronically rather than just turn the key. He's wants to bypass the relay and the high pressure gas pump and figure out if, not only is the pump working, the pump is pumping good pressure.

It's an Airtek model. Sure wish I had known PartsguyEd when I bought this seeming pile of garbage.

I'll let you know how it goes. If you have any ideas in addition to turning the key, that'd be great.

IF its not that (the midship fuel pump), then things get interesting.

 

If he grounds pin #6 of the EEC self-test connector (or shorts pin#2 to pin #6) and turn on the key the selected in-tank pump and the frame pump will run as long as the key is on. The fuel test point on the fuel manifold should read 43-45 PSI.



The relay below in the diagram is for and upgraded relay and will not be like your factory realys.


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It took long enough to fix, but you were right subford, the brand new midship in-line fuel pump was not working. We replaced it after checking all of the electrical connections, and now: Everything works!!

Thanks for your help. Til the next time,
Michael