I have an 87 E350 with the 351W factory Holley carb and dual tanks. I need help diagnosing a problem with my tank selector switch- it has stopped functioning a few times and left me stuck on the empty tank! Also the fuel gages for neither of my tanks work. Below is a pic of my switcher module, does anyone have a wiring diagram for this? I think one of the wires should read +12V when the front tank is selected. Are the other 4 wires for the gage readout?

 

Here's a diagram for a truck. If your wire colors are the same, I bet it's wired the same.

 

I don't have the hot fuel setup, would this diagram still apply?

 

I am not sure, the vans were a little different sometimes. What are the colors of the wires on the valve?

 

Well my front tank is definitely not working!

I checked all the wires with a multimeter and none of them showed any voltage with the key on and the tank switch in either position. From left to right the wire colors are:
Orange
Green
Green/Red
Brown/Orange
Yellow/Red

Any diagnostic ideas?

 

OK, I think I'm on to something... I've been searching and found this link:
https://www.ford-trucks.com/forums/1...nk-wiring.html

In it is this diagram for the switch which has wire colors that match mine exactly:


I think I'm going to take apart the switch and make sure it's functioning correctly. Does anyone have a diagram that shows where each of the wires at this switch go? I need to know which should be power to the valve...

 

Here is from a 1981 Econoline van, the colors look to be the same so I'd guess it's valid for you.

From the 1981 factory wiring diagrams manual (light truck).

 

Thanks!

1 Thing I don't understand: The 1981 and 1985 vans had the 1-wire tank switcher valve where mine has 5 wire motorized tank switcher valve. On my van I would guess that one wire is +12V when the switch is flipped for the front tank and reads 0V when the rear tank is selected. What are the other 4 wires for? Based on your diagram I see that 4 of the wires at the switch are associated with the fuel tank sending units... The colors at my selector valve match exactly so could these be the same circuits? Could these extra wires be part of a harness for the hot fuel system (which my van did not come with)?

 

If you have a motorized selector valve, all bets are OFF!

I have no idea about the wiring on those things, maybe somebody who knows more will chime in...

Might also investigate some generic Pollak motorized switcher valves just to learn from them and their wiring:

Let me google that for you

Might also ask in that thread you posted earlier from the Vans forum, maybe subford will respond.

 

Yeah, the wiring is wierd. I can see the harness that takes the fuel sender wires up to the dash and I don't know why they'd turn around and route the signal back to the tank valve. I think I'm going to replace this valve whether or not it's the problem... I don't want to get stuck without gas again! I noticed that autozone has what looks like the same part for $76... It comes with the switch and harness adapter too.

Duralast/Fuel Tank Selector Valve (FSV2K) | AutoZone.com_

 

Since your wire colors match the sending unit wires, then yes your sending units are switched electrically down at the valve. They don't double back the wires. You should only have one single wire going up to the cluster from the valve. You then have each sending unit wire going to the valve, and the valve puts either one on the single wire going up to the gauge in the cluster.

If you have the motorized valve, the the stores usually stock and sell the pollack valve, and though it's not plug and play, it functions the same and can be made to work.

 

Great, so that means if I ground the green wire (wire to the fuel gage) it should show a full tank, correct?

 

What we generally do in this forum is tell people to disconnect the connector from the sending unit, and ground out the colored wire with the key in ACCY or RUN. That will make the gauge swing to Full, disconnecting (ungrounding it) will make it read below empty.

Obviously, the selector valve will need to be set to the tank you're testing.

 

Thanks CTUbutis I'm going to try this. Also, i confirmed the sender wires go through the tank selector valve.

Here's a new finding: I noticed the "module" fuse was burnt out... Could this have something to do with the fuel system?

 

Oh, I don't know, can't say I've ever heard of a "module" fuse before.........?