82 Ford E-150 Fuel Gauge Problem

[Jim Oaks]

The fuel gauge in my '82 Ford E-150 van quite working. It has a dual tank setup, and both tanks work, but I think the gauge quit working when I switched from the rear to front tank.

I ran a jumper from the sending units ground wire to the frame to make sure it was grounded. Gauge still didn't work. Unless it's a connection in the switch, I can't figure out the problem. A faulty fuel gauge is usually a ground problem.

This is the metal toggle switch under the dash style.

Anyone have any experience with this?

 

[Jim Oaks]

Man. Now I'm not sure if it's even switching tanks. It has a solenoid on the frame rail with a line from each tank coming in, and one going up to the manual fuel pump on the block. It clicks when you flip the switch to change tanks.

The switch also controls which gauge is read. I haven't found a replacement if it's bad.

 

[RonD]

The fuel valve is a simple 12volt on/off valve, 0volt = tank 1, 12volt = tank 2

Google: Universal Fuel Tank Switch

If you have a mechanical fuel pump and carb then the Dual Tank switch in the cab will just be a double throw double pole switch.
This is in essence two separate switches controlled by one "lever"

The fuel gauge is connected to a pulsed 5volt regulator, this power passes thru the gauge to the sender in the tank which is a variable resistor and then to a Ground.

Battery-----Pulsed 5v-------Gauge-----sender----ground

For dual tanks is would look like this:
Battery-----Pulsed 5v-------Gauge-----Switch----sender 1----ground
....................................................................\---sender 2----ground

So the switch will have 3 "gauge" wires, 1 coming from the gauge, 1 from each sender.

You can't measure pulsed voltage, but if you hook up a test light it should go on and off with key on.
You can measure OHMS on the Sender wires, pre-'89 Fords use this range:
73-10 Ohms
73 = Empty
10 = Full

If you hook up an OHM meter to one sender wire and then add some fuel to each tank you can tell which is which, or look at the wire color.

If OHMs on one stay at around 73 then that float is no longer a "float", it is a "sink", lol.

So the Double Pole Double Throw switch will have 3 contacts on one side and 3 contacts on the other side.
Each set of 3 are separate, no internal connection.
On one set you will have just 2 wires, one will have 12v when key is on(center pin), the other one will run to the Fuel valve.
So when switch is push one way Fuel valve will get 12volts, pushed the other way Fuel valve gets 0volts.

Other set of 3 will have 3 wires, center pin will be from Fuel Gauge, then each sender wire to one of the outside pins