Fuel Gauge problems 79 scottsdale

[Dillon79scotts]

I have always had problems with the trucks fuel gauge, the needle is always sitting at about 3 o clock way past the full mark no matter how much fuel it has.

I am looking to find a wiring diagram to figure out if its bad wiring or in need of another gauge.

If anyone has had problems with the duel fuel tanks and can help

[randy92782]

Clean your grounds. I believe that is what causes it

I have yet to fix my own though

[Dillon79scotts]

Do the fuel wires go into the big plug-in in the back of the cluster? or is there a seperate plug. Also where are the grounds

[Dillon79scotts]

i also have a wire that isnt even hooked up, that looks like it goes to the tank solenoid on the frame rail, i think it is a sending wire to a tank? not for sure tho

[randy92782]

Originally Posted by Dillon79scotts

Do the fuel wires go into the big plug-in in the back of the cluster? or is there a seperate plug. Also where are the grounds

Should be a ground going up to the filler neck.

The wire does go into the cluster andI believe it to be pink. I'd have to look again. Been a while since I looked at mine

[Dillon79scotts]

ok ill check it out.

what else could be the problem here? could it be the solenoid switching the tanks over? I have had someone under there and you cant hear anything when you flip the switch for the other tank but im assuming it works because it runs on the tank i have it on

[randy92782]

Originally Posted by Dillon79scotts

ok ill check it out.

what else could be the problem here? could it be the solenoid switching the tanks over? I have had someone under there and you cant hear anything when you flip the switch for the other tank but im assuming it works because it runs on the tank i have it on

No clue how the dual tanks work. I have never had any that worked

[Dillon79scotts]

I am trying to find a wiring diagram For it. But no luck

[GMCTruxrule]

I use to run out of gas all the time cause my fuel gauge was all over the place.

Now i run a fuel cell in the bed and I have yet to run out of gas. But of course, it helps actually being able to see the fuel level....

[randy92782]

Originally Posted by GMCTruxrule

I use to run out of gas all the time cause my fuel gauge was all over the place.

Now i run a fuel cell in the bed and I have yet to run out of gas. But of course, it helps actually being able to see the fuel level....

In my old truck I used to have a boat gas tank in the bed. It was kind of hack and was nice to be able to see how much gas you had but you had to be in the back of the truck or find a ladder. 9" lift and 39's was a little too tall

[GMCTruxrule]

40"s and 7 inches. No ladder, just tall enough to see.

[randy92782]

Originally Posted by GMCTruxrule

40"s and 7 inches. No ladder, just tall enough to see.

I'm 6'4" Still wasn't tall enough

[Duallie]

GM gas gauges all the way to the right is an open circuit (broken wire). All the way left means the sender wire is shorted to ground somewhere.

[Dillon79scotts]

Originally Posted by Duallie

GM gas gauges all the way to the right is an open circuit (broken wire). All the way left means the sender wire is shorted to ground somewhere.

A broken wire, okay well that has to be the problem then, I have looked all the way uP the frame rail. Could it be that one of the sending wires to the tank is off?

The wiring is pretty bad on the truck, so I'm thinking it's between the switch and the wires to the gauge

[Duallie]

Short the tan wire (the wire to the sender) to ground with power on to test the gauge itself. If the needle moves left, then the gauge and the tan wire up to where you grounded it is OK.
I have seen two kinds of dual tank systems in your generation of truck. The older kind has a single-wire/3-port solenoid and the tank sender is selected at the dash switch. The newer kind has a (5?)-wire/6-port electric motor-activated solenoid and the sender is selected at the solenoid. The difference happened when return lines were needed back to the fueltanks.

[Dillon79scotts]

Originally Posted by Duallie

Short the tan wire (the wire to the sender) to ground with power on to test the gauge itself. If the needle moves left, then the gauge and the tan wire up to where you grounded it is OK.
I have seen two kinds of dual tank systems in your generation of truck. The older kind has a single-wire/3-port solenoid and the tank sender is selected at the dash switch. The newer kind has a (5?)-wire/6-port electric motor-activated solenoid and the sender is selected at the solenoid. The difference happened when return lines were needed back to the fueltanks.

Okay, that's the wire that plugs into the solenoid on the frame? There is a pink with a thin black stripe on t that. Comes off the switch in the cab, can you tell me if thats power? It was hooked the fuse block but was some screwy connector so I took it off.

And mine is the switch in the cab with the single wire to the solenoid and it's a 3 port

[Dillon79scotts]

Originally Posted by Duallie

Short the tan wire (the wire to the sender) to ground with power on to test the gauge itself. If the needle moves left, then the gauge and the tan wire up to where you grounded it is OK.
I have seen two kinds of dual tank systems in your generation of truck. The older kind has a single-wire/3-port solenoid and the tank sender is selected at the dash switch. The newer kind has a (5?)-wire/6-port electric motor-activated solenoid and the sender is selected at the solenoid. The difference happened when return lines were needed back to the fueltanks.

I'm not sure what wire from where.or where it's at, that tan one

[Duallie]

Power comes from the fuseblock to the selector switch, then turns the fuel solenoid ON for one tank and OFF for the other tank. I don't remember the color of the wire going to the solenoid. I seem to recall that ON was for drivers side and OFF for passengers side, but I could be wrong on that. A separate circuit on the dash switch also swaps the tan sender wire to the appropriate tank.
Does your tan level sender wire also plug into the fuseblock? I have seen that, but don't remember if its on GM cars or trucks.

[Dillon79scotts]

Originally Posted by Duallie

Power comes from the fuseblock to the selector switch, then turns the fuel solenoid ON for one tank and OFF for the other tank. I don't remember the color of the wire going to the solenoid. I seem to recall that ON was for drivers side and OFF for passengers side, but I could be wrong on that. A separate circuit on the dash switch also swaps the tan sender wire to the appropriate tank.
Does your tan level sender wire also plug into the fuseblock? I have seen that, but don't remember if its on GM cars or trucks.

The solenoid underneath is working I know for sure. But after that I'm lost on the wiring. From there after idk where they really go

[Dillon79scotts]

Originally Posted by Duallie

Power comes from the fuseblock to the selector switch, then turns the fuel solenoid ON for one tank and OFF for the other tank. I don't remember the color of the wire going to the solenoid. I seem to recall that ON was for drivers side and OFF for passengers side, but I could be wrong on that. A separate circuit on the dash switch also swaps the tan sender wire to the appropriate tank.
Does your tan level sender wire also plug into the fuseblock? I have seen that, but don't remember if its on GM cars or trucks.

The solenoid underneath is working I know for sure. But after that I'm lost on the wiring. From there after idk where they really go. I have a wire hanging with no idea where it goes. It has one of those 90 degree plug ins on it then it's bare. Wiring diagram would really help

[Duallie]

Where is it hanging? At the fuseblock, or under the cab? Is it a plastic-covered 1/4" spade?

[Dillon79scotts]

Originally Posted by Duallie

Where is it hanging? At the fuseblock, or under the cab? Is it a plastic-covered 1/4" spade?

Yes, it was the sending wire. I did the ground and it went all the way down. It had also. Ripped apart by the starter in that wire loom. It works now. Thanks for the help everyOne