Dual tanks work, but maybe not switching the gauge?

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JM in KY

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I’ve recently replaced the fuel selector valve on my 87 GMC R1500. Also replaced the switch inside the cab. I’m pretty sure the tanks switch, because I can hear a change in tone under the truck when I select the right tank (like the right pump makes a slightly different noise).

However, there’s no change in the fuel gauge when I flip the switch. Both tanks were full a week ago, but I’ve driven about 50 miles only on the right tank since then. Maybe I just need to give it some time and more miles to run more gas out of one tank, but it behaved similarly before replacing the valve and switch. The main difference was the truck would instantly die when switched to the right tank before I replaced those parts. Fuel gauge didn’t seem to change then either.

Ideas? Is it possible to switch the tanks but somehow only get fuel level readings from one tank? All the wiring I’ve encountered so far appears to be original. I’ve not found any splicing or re-wiring anywhere in the truck.
 

Tank6x2

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I’ve recently replaced the fuel selector valve on my 87 GMC R1500. Also replaced the switch inside the cab. I’m pretty sure the tanks switch, because I can hear a change in tone under the truck when I select the right tank (like the right pump makes a slightly different noise).

However, there’s no change in the fuel gauge when I flip the switch. Both tanks were full a week ago, but I’ve driven about 50 miles only on the right tank since then. Maybe I just need to give it some time and more miles to run more gas out of one tank, but it behaved similarly before replacing the valve and switch. The main difference was the truck would instantly die when switched to the right tank before I replaced those parts. Fuel gauge didn’t seem to change then either.

Ideas? Is it possible to switch the tanks but somehow only get fuel level readings from one tank? All the wiring I’ve encountered so far appears to be original. I’ve not found any splicing or re-wiring anywhere in the truck.
Check the tank level wire top of the tank
 

Ron Sebastian

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Ron
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Long shot, but after a lot of parts changing, a bad ground on the switch cured a big problem of gauge not reading right. Check your ground wire and ground to the switch.
 

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