Tank Selector Valve

[jimi121v]

Anybody know if the selector valve ckt has its own fuse, or which ckt it shares with? Is there an online wiring diagram? I have no voltage to the valve with the switch in either position. I pulled the conector off the switch in the cab, & dont see voltage there either. It is a 1980 with the 6 port/single wire valve. The fuel gage works just fine for both tanks.

[VetteVet]

I don't know how close this is but it's all I have so I hope it helps. I forgot to say that in your trouble shooting DO NOT put any voltage to the tank sender wires.

[jimi121v]

I have seen this drawing before, but it is different than the switch on my 80 GMC. I have a five post switch. My fuel gauges work fine. The side of the switch that controls the valve has no voltage. I have traced the dark green wire (the hot side of the switch) to the fuse block. It goes into a connector at the upper right hand corner of the fuse block. It looks like a relay that plugs into the connector. Is that the horn relay? The horn fuse is blown, and blows the instant I put a new fuse in. I guess I will dig into that problem, and see if it fixes both problems.

[jimi121v]

Originally Posted by mitch1965

I don't believe that there is voltage when the switch(in the cab) isn't being pressed, as it is a momentary solenoid. Pressing the switch for either side will energize the solenoid, causing it to physically move inside. Once you let go of the switch, the solenoid stays in that position, connecting the proper fuel tank line to the engine and fuel level sender to the gauge.

There would still have to be voltage to the switch. My truck does not have that type of switch anyway. I have actually taken the switch apart. The way it works is by sending votage to a solenoid at the valve when you select the left hand tank. It removes the voltage when you select the right hand tank. So if you have no voltage it will always default to the right hand tank unless the valve is actually siezed. This is the older version with a five post switch, and a single wire valve.

[jimi121v]

The relay in the upper right hand corner of the fuse block is the tank selector valve relay. It is no longer available from GM or any of the parts stores that I have checked with. I have pulled the relay & verified that the input is hot with the key on, and the ground terminal is grounded. The relay does not opperate, so I left it out, and made a jumper with an inline fuse to connect between the hot terminal and the valve ckt terminal. The ckt is complete now and I can hear the solenoid opperate. I'll find out tomorrow when I head home if the valve is still any good.

[jimi121v]

It worked like a charm!!! I am going to make a connector out of the old relay with the inline fuse attached. It will just be a much more secure way to make the connection. All the info I have found online about this relay mentions the year 1980. It is possable that this setup was one year only. Anybody know anything about that. The relay can still be purchased from obsolete parts dealers, you can also have your local dealer do a system search to find GM dealers that still have one in stock.