Fuel gauge (dual tanks)

[Busaman]

I have an '85 Silverado K-10 dual fuel tanks. When I switch to the right side the fuel gauge goes past F (FULL). The left side tank seems to work good.
Thoughts?

 

[oopsman_09]

mine does the same thing. but only part of the time. I think mine is a bad ground somewhere. yours could be the same or a bad sending unit.

 

[1ATony]

Welcome to the gmsquarebody forum

 

[Boone83K10]

you need to clean/repair the ground strap. The ground is located on top of the frame. You can see it/the hole it is supposed to be in if you look down between the bed and cab on the passenger side. clean it with a wire brush. If that doesn't fix it, it may be a bad ground on the sending unit itself inside the tank.

 

[chengny]

Diagnostic flow chart for the dual tank switch:

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First thing to check is just as Boone83K10 suggests; a good ground connection at the common grounding buss bar (mounted on the LH inner fender wall behind the dash).


Here is a link to a thread that discusses the system in detail - another member had a similar problem about a month ago. Turned out to be a bad dash gauge - but in his case neither side read correctly:

http://www.gmsquarebody.com/forum/showthread.php?t=6304

 

[Busaman]

thanks guys.

 

[Busaman]

Since my last post, the left side quit working as well. Its sits directly at 3 o'clock. When I shut the truck off, it goes to full. When turn to key, the gauge goes to 3 o'clock.

 

[GTME94]

I cleaned the ground to frame for my LH side gage and it started working properly. I need to do the same for RH side but it is behind the shield for the fuel tank switching valve and I didn't have time to get it done.

 

[Busaman]

Thanks can you me tell exactly where its at on the truck? I've been underneath the truck. I see a black wire bolted to the tank. Did you remove the bed to get to your connections?

 

[chengny]

Empty the tank. Release the brackets from the frame and lower the tank. There is sufficient slack in the wiring and tubing. At least enough for you to rest the tank bottom on a milk crate without straining them. Then you can take your time cleaning up your connections.

Oh yeah, undo the clamps on the tank fill and vent hoses.

But I would not get your hopes up that you have two bad grounds develop within days of each other. It might well be that the switches in the tank level indicating portion of the Pollak valve are screwed up.

 

[Busaman]

So I 've got my left tank down and haven't located the selector valve. Could anyone tell me where this is located???

 

[foamypirate]

So I 've got my left tank down and haven't located the selector valve. Could anyone tell me where this is located???

Passenger side, right underneath the rear of the cab next to the inside of the frame rail. It's under a metal shield typically.

 

[Busaman]

Thanks sir!

 

[Boone83K10]

the ground for the RH tank is visible by just standing next to the truck. If you look down between the cab and bed, you can see it on the frame. If that doesn't work, it may have come off the small post that it connects to.

 

[Busaman]

Thanks again for the help guys. The drivers tank had a broken ground wire and the passenger side sending unit was bad. Thanks again for everyones advice.