Dual fuel tanks

[20venom08]

Idk if there is a post or tread on this subject so sorry if I'm repeating someone but I have a 1985 c10 silverado with dual fuel tanks and the driver side when I flip it to that fuel tank the needle goes way past the full line and I bought the truck with this issue so idk if there is gas or not but passenger side works just fine. He said he never used the driver side so I was wondering what I can do to get it working again. I heard it could be the sending unit or floater and one guy said the gauge is broken but if that was the case the passenger side wouldn't work or read. Thanks in advance for any help.

 

[Driver4r]

Check the grounds.

 

[philjafo]

It's either the sending unit or the wiring in between the switch and the sender. IIRC the sender is 0-90 ohms, as the float goes up so does the resistance. Going way past full indicates an open circut, use a meter and pull the wire from the sending unit and check resistance to ground. If you get anything other then open you have a broken wire somewhere start tracing the wire back to the switch. If you get an open at the sender it likely needs to be replaced. BTW I might have it backwards and high resistance would indicate a short circut, maybe someone else on here knows for certain, but the basic troubleshooting would be the same. Isolate the sender and check resistance to ground.
And just like driver said the tank needs to be grounded to the frame, needs to be grounded the body, needs to be grounded to the battery, needs to be grounded to the frame, and they all have to be clean.

 

[20venom08]

Ok thanks Phil yeah driver side tank hasn't been used leat two years from what he was saying would it hurt if I switch to driver side tank and run it see if there fuel in there

 

[philjafo]

I wouldn't put two year old gas into a carb, better to disconnect the lines and pump any old gas out.

 

[Stroked]

I've had this problem on 3 different squarebodies and it was a bad ground from the sending unit to the frame every time. I would check that first and if that doesn't work then follow Phil's instructions.

 

[Driver4r]

I wouldn't put two year old gas into a carb, better to disconnect the lines and pump any old gas out.

You could dilute it 50/50 or 75/25. And burn it out that way.

 

[chengny]

GM Diagnostic Chart for Auxiliary Fuel Tank:

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And, just as per Mr. Stroked suggests - the first step in the trouble shooting process is check the ground connection at the buss bar.

And a nice clean wiring diagram:

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And some info on the 6-port Pollak Valve.


Spec sheet:

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Good diagram of connections:

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