Fuel sending unit wire

[Tuckerjr]

Hi guys, I need some help. I am trying to get my fuel gauge working on my 74 dart. I have taken the instrument panel out and tested the gauge with some AAA batteries and it is fine. I replaced the voltage regulator with a solid state chip, capacitor, and heatsink. The temerature guage does not work either but the rest of the instrument panel lights do, (voltage, illumination, brake, etc.). I tried grounding the wire from the fuel sending unit and turning the switch on and the gauge doesn't move. I traced the wire up from the trunk along the sidewall up to the fuse block. I tried using a test light on the wire at this point while turning the ignition on to see if any power was in the wire and found none (not sure if this is a viable way to testing it, I have a multimeter I could use).

I also found a light purple wire coming from the firewall running under the dash that has gotten hot and lost all it's insulation (was that way when I got the car). It has an aftermarket gage cluster attached under the dash to read water temp and oil pressure. I am thinking that maybe this melted wire is somehow related to the gages not working and therefore they moved to the aftermarket gages.

My question is can anyone point me in the right direction to go from here.

Also if anyone can post a link to a wiring schematic it would be a great help, would love to lose this 5 gal can of gas in the trunk I'm riding around with.

Thanks,
Russell

 

[67Dart273]

If the temp gauge isn't working, you still may have a problem getting power to the gauges. Here's the general flow

The instrument limiter gets 12V in run from the key, drops down the voltage, and splits it off to any instruments, gas, temp, oil.

You should be able to GROUND the sender end of either the gas or temp gauge with the key in "run" they should peg.

There is no power "from" the sender. The sender end of the gauge goes directly to the trunk through one wire, to the sender, through the sender to ground.

So you should be able to check continuity of the wire / sender with a meter. IF you doubt the sender is working, pull the wire off the gauge and tank, and ground one end with a clip. Then you can use your meter/ light and a battery to check continuity.

MAKE SURE the sender is grounded. There normally is a clip that jumpers across from the metal line on the sender, across the rubber connector hose, and clips onto the metal fuel tube heading up front. It doesn't matter if you have that exact clip, so long as the sender is grounded.

One way to check "end to end" and remove the sender from the equation is clip a ground to the sender end of the wire. If the gauge is working, it should peg full with key in run.

 

[Tuckerjr]

Thanks for the quick reply. I tested continuity between the fuse block and the sending unit end of the wire and it is good. Next I grounded the sending unit (it also has the ground strap on it) with a wire with alligator clips on each end. Still nothing. I will try grounding it better tomorrow (it's dark out now) and see what happens. I tried grounding the sending unit wire, still no movement on the gage.

Could I possibly have a bad ground on the cluster? Or a bad trace? My illumination lights work on the cluster but is it possible to be recieving a ground through the voltage gauge? I need to find the wire to the temp gage and ground it and see if it moves, it's probably not hooked up since the aftermarket gage cluster is hooked up.

 

[Tuckerjr]

It's also possible I could have a bad pin on the instrument cluster, I found a schematic and believe I need to check pin number 2.