need advice in gas gauges in blue truck

[1low4x4]

Hey dudes in my blue 85, which has dual tanks, when ever either one is full the gauge reads 1/4 tank. Moves on down to about an 1/8th inch below empty when they are empty.

Gauge acts the same when either tank is activated.

Grounds or back gauge?

Isn't there a resistance you can check on the gauge itself? What is it and how?

 

[Boone83K10]

The gauge reads 0-90 ohms. 0 is empty and 90 is full. It gets the signal from the sender, but on dual tank trucks, the signal passes through the selector valve.

1. Check your grounds for the fuel sender. Driver side is under the bed next to the mount for the fuel line holder. Just look between the cab and bed on passenger side and you should see a ring terminal on a bolt. That's passenger ground. Then check that those two wires are securely pushed onto the post at the tank sender. You can usually see those by just sitting in the ground and putting your head in the rear wheel wells.

2. Check the connector at the selector valve. Make sure it is secure. It is inside of passenger frame rail under the cab.

3. Check the regulator on the back of the gauge cluster.

4. Last check the pins on back of fuel gauge. Clean them and see if they are receiving the 0-90 ohms.


My gauge did same thing, turned out to be selector valve malfunctioning. It was reading both gauges electrically even though it was fully switching mechanically.

 

[J Knight]

My stock gauge did the same thing and when I replaced it with a tach/fuel gauge combo the fuel gauge started working correctly. My bet would be the gauge or gauge connection in the cluster.