Fuel gauge connection?

[insidegroove]

I got my first 69 Roadrunner 3 weeks ago. I just finished upgrading all the safety stuff....now im trying to get the fuel gauge working. i pulled the gauge panel out and flipped it over and this is what i have.....are there supposed to be wires attached to those posts/screws under the voltage regulator (i think thats what that is). i have the ground strap on the front of the fuel tank, and theres a black with coming out of the sending unit opening area that attaches to a small post/screw. what else am i missing? what gets power up to the gauge?

 

[69hemibeep]

That rectangular thing plugged in there is a voltage limiter which suppies about 5 volts to the gauge

 

[insidegroove]

That rectangular thing plugged in there is a voltage limiter which suppies about 5 volts to the gauge

i know that part......my confusion is how does the signal from the fuel sending unit in the tank reach the fuel gauge on the dash?

 

[quikbird]

Wire runs from the tank to the dash. Not sure but think it is brown

 

[Carl Ray]

No wires under those nut. Printed circuit transmits power to voltage limiter then gauge, other side is ground that goes thru printed circuit, out the round connector and to tank. What are symptoms with gas gauge? Does temp gauge work? Both get power from voltage limiter

 

[69hemibeep]

Round connector with all the pins

 

[insidegroove]

thanks everyone....i used a wire brush and cleaned up everything in the ground strap area. Then i disconnected the black wire at the sending unit and clipped one end of a grounding wire to it and ground the other end of the grounding wire to the chassis (sanded it down to bare metal) turned the key in the ignition and the gauge didnt move. so i believe that means it's either the sending unit of the little voltage regulator thingy on the back of the gauge cluster. ill start with the regulator first because its cheaper.

 

[69hemibeep]

You have a problem some where in the wiring or gauge. You could pull the drivers side kick panel off unplug the harness ground it at that point and see if the gauge moves. Next step would be the round plug on the circuit board or in any order you want if the cluster is out I'd go there before the kick panel

 

[Carl Ray]

By grounding wire you took sending unit out of the circuit, so sending unit is not the problem. If your original temp gauge works it's not the voltage limiter. Unplug harness at kick panel as suggested, ground sending unit wire, no gauge movement move to the next connector.

 

[mac]

here you go

 

[insidegroove]

By grounding wire you took sending unit out of the circuit, so sending unit is not the problem. If your original temp gauge works it's not the voltage limiter. Unplug harness at kick panel as suggested, ground sending unit wire, no gauge movement move to the next connector.

ok i removed the kick panel today. i traced the wire coming from above the gas tank in the trunk (blue) and it went up and over the left rear fender, down along the bottom of the door and came to a plug behind the kick panel. i disconnected the plug and i grounded the blue wire that continues up to the gauge cluster.....i was excited to see the fuel gauge move for the first time. So i know the gas gauge works (it pegged itself up to full), and i know the voltage regulator works. i plugged the plastic plugs back together and the fuel gauge doesnt move. does this mean the sending unit is bad? or does it mean i need to replace the wire that is going from the fuel tank (inside the trunk) to the plastic plug behind the kick plate?

 

[Carl Ray]

In a previous post you mentioned you cleaned and grounded the "black" wire at the sending unit connection and nothing happened with the gauge. Did you misspeak and mean Dark Blue or did you ground a black wire? If black is all you have there coming out the harness, someone spliced a black wire onto the dark blue and that connection could be your problem. You should have 1 wire at the sending unit and it should be blue. You may a wire going to ground, if so it is probably black. Ground the dark blue wire at the sending unit with the plug behind the kick panel connected and report back.

 

[Russ69Runner]

Check to see if your tank is grounded well also. There is a clamp that goes to the fuel line to insure a good ground. Would suggest having a good frame ground also is a good idea. Remember the wire going to the sending unit is a ground wire to make that gauge work. The amount of resistance the sending unit put out determine the impedance of the gauge.

 

[insidegroove]

the first photo is what i have down at the fuel tank......grounding strap looks good, i scuffed all underneath it so its getting good metal to metal contact. the wire right next to it appear to be black.....i sprayed degreaser and scrubbed it just to be sure. is that the same wire that comes out the top and into the trunk? is it one continuous wire? the wire inside the trunk is definately blue so thats why im not sure. are you saying i should make a second ground by splicing into that black wire at the front of the fuel tank and grounding it somewhere on the chassis?

 

[Carl Ray]

No, do not splice and ground the black wire. It is the "sensing" wire, its resistance to ground via the tank sending unit is what the gauge reads. If you ground it permanently the gauge will read full for awhile until it burns up. You can add a ground wire to the grounding strap to ensure you have a good ground. The wire inside the trunk has been painted, so its probably black. Trace it back toward the front of the car and find where it attaches to the Dark Blue wire in the connector you found at the kick panel. Maybe someone replaced the entire wire. When looking at the connector at the kick panel, you have a Dark Blue wire that goes up to the cluster, is the corresponding wire going to the trunk Dark Blue also or black? Based upon your earlier testing, where you said grounding the black wire at the sending unit had no impact on gauge so there is an open in the Black/Dark Blue wire between the kick panel connector and sending unit.

 

[insidegroove]

No, do not splice and ground the black wire. It is the "sensing" wire, its resistance to ground via the tank sending unit is what the gauge reads. If you ground it permanently the gauge will read full for awhile until it burns up. You can add a ground wire to the grounding strap to ensure you have a good ground. The wire inside the trunk has been painted, so its probably black. Trace it back toward the front of the car and find where it attaches to the Dark Blue wire in the connector you found at the kick panel. Maybe someone replaced the entire wire. When looking at the connector at the kick panel, you have a Dark Blue wire that goes up to the cluster, is the corresponding wire going to the trunk Dark Blue also or black? Based upon your earlier testing, where you said grounding the black wire at the sending unit had no impact on gauge so there is an open in the Black/Dark Blue wire between the kick panel connector and sending unit.

yeah the wire in the trunk has definately been painted but as i followed that particular wire all the way up to the plastic connector behind the kick plate.....the wire is still blue (just a different shade of blue from what they painted over in the trunk). and that same blue wire continues up to the gauge cluster after the plastic connector.

 

[Carl Ray]

Disconnect wire from sending unit and kick panel. Put ohmmeter leads on both ends of wire, read resistance. If OPEN or OL, wire is broken somewhere along its path.

 

[insidegroove]

Disconnect wire from sending unit and kick panel. Put ohmmeter leads on both ends of wire, read resistance. If OPEN or OL, wire is broken somewhere along its path.

im probably driving you nuts and i apologize. when you say disconnect the wire from the sending unit.....would that be the black one i have coming out the front of the fuel tank or do i need to remove the sending unit and disconnect a wire on the unit?
p.s. i found in my wiring diagram that the fuel gauge wire IS supposed to be dark blue.

 

[Carl Ray]

Yes, disconnect black wire from sending until, do not remove sending unit. Attach one lead of your Ohmmeter on to the black wire at the sending unit, attach the other ohmmeter lead to other end of the same wire where you disconnected at the kick panel. Ohmmeter should read 0 resistance or close to 0. If not, you have a bad wire. This is all assuming you have an ohmmeter.

 

[Russ69Runner]

No don't ground the black wire run a ground wire to the fuel line separate to the body. That is what I did to make sure it did get the tank grounded well. To make sure my car grounds were always going to be good ran a #6 wire all the way through the car and branched off with number 10 wire too other parts of my wiring. Bolts get rust and a good ground is something that will make sure everything works well. Nothing like not getting a ground to a circuit will drive you nuts. Good luck on the car.