How do you test if dual tanks are working?

[JacobSchni]

I have new tanks and sending units, and I wanna use both now. old ones were rusted. When I push the switch in the cab, is there a indicator or anything to tell me if it actually switched? If there is a problem would it be the selector valve or the switch? how would you test those?

[JacobSchni]

by the way its the newer style selector valve with multiple wires, not just one.

[Dannyboy1966]

your fuel gauge should start showing how much fuel you have in the new tank you just switched too.

[MountainGoat1966]

You will notice the switch is spring loaded.
When selecting the other tank, the recommended procedure is to hold down the switch firmly to the desired tank for a few seconds, then let it spring back to its running position.
Sometimes it takes a couple seconds for the valve solenoid to respond completely.
What goes bad? Sometimes the switch fails, other times the solenoid valve thingy fails. I replaced both on my '83 to get both tanks working. It was expensive but well worth it.

[rajincajintj]

Originally Posted by Dannyboy1966

your fuel gauge should start showing how much fuel you have in the new tank you just switched too.

just an FYI. it could read from the other tank, but might not actually be pumping from that tank. mine does this, but will not pump from the pass side tank.

[rajincajintj]

Originally Posted by JacobSchni

by the way its the newer style selector valve with multiple wires, not just one.

i found this on another site in my research:

The whole system is really simple.

You have a power and ground going to the swtich, then through the firewall to a connector that is just for it. They follow the main harness back to the valve along with the wire for the sending unit that comes out of the fuse block connector.

the valve is not grounded. It gets power and ground, from the wires directly from the switch. The switch just momentarily crosses the wires.. IE. + - to go to one tank, and - + to switch the other way.

The other 2 wires go to the sending units.

So, 5 wires total at the valve: two power wires (yellow and green I beleive) and 3 pink wires. the two from the sending units, and one from the guage.

The wires going to the switch are pink and black. the black one goes to a ground point above the parking break assembly. The pink goes to the top of the fues box for a switch 12V source.

The switch is a very common wear item, and the dealer sells them for 11 dollars. The valve is less likely to fail, and much more money from the dealer.

good luck.

[SkinnyG]

You could get some lacky under the truck listening for the "switch."

The one my truck came with would not switch, but the gauge would.

The junk yard replacement would switch, but the gauge would not.

I went new on the next one.

[TKCR]

When I switch mine, I notice the needle moving on the fuel gauge as soon as it's switched to the other tank.