Dual Tank Switch Dilema

[Lowered87]

Usually the problem is the wrong switch, broken wires or bad ground from the sending unit to the frame. The worst is you are dropping your tanks or taking your bed off. It totally makes sense with a wiring diagram, the correct parts and being able to work on it properly.

I have wasted so much time trying not to remove the tanks or bed that in the end I would have completed the job quicker by dropping the tanks. Also, the wires are all taped together with 666 other wires that the last owner cut off and left in place or used wiring nuts to make connections. My other favorite is the overlength wire rolled in a loop hanging down with 20 pounds of mud hanging off of it. I only purchase the trucks with 77 wiring gremlins for free.

 

[Raybob9289]

Sorry about that. I knew we had done it I just didn't remember that we were buying a different switch. Though you might be disappointed to be running the pollak switch you'll be very happy with the reliability of that system.

I still owe you a sixer

 

[calredneck]

If I under stand it 73 to 80 the switch changes the sending unit to the Gage in the 81 to 87 the switching vavle under the truck switches sending unit to the Gage

 

[Lowered87]

1973-1991 Dual fuel tank systems theory of operation - The 1947 - Present Chevrolet & GMC Truck Message Board Network

1973-1991 Dual fuel tank systems theory of operation The 1973 - 1987 Chevrolet & GMC Squarebody Pickups Message Board

67-72chevytrucks.com

If you look at this link, there is so much stuff, you should have no problem understanding.

 

[Lowered87]

This is from LMC Truck. You can download a free catalog that is like a parts explosion. There are 13 different types of #15. Items 16, 17 and 18 are determined by year and so are the wiring harnesses and tank switch. It is all one set depending on year, # of tanks, fuel type, fuel delivery. As for the sending unit, it really depends on your fuel pump on the side of the engine. Some have fuel return and some do not. The other is the vent line that would normally run to the charcoal canister. I vent to atmosphere on the frame through gearbox vent fittings made by John Deere. Hose from the sender bolted to the frame with the piece that stops dirt from getting in and plugging the line. The return outlet I did not need so I capped it. My truck happen to use the older style wiring 3 port single wiring because the frame was from the 70s but everything else is from the 80s. That is what is great about squares, everything bolts to everything. Needless to say my truck is not a Barrett Jackson, numbers matching princess. Frankenstein but all OEM metal.

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[Raybob9289]

With the correct ****** switch it works perfect..

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