Fuel gauge wiring

[bnoon]

All I can find in searches is "check your grounds" or how to power aftermarket fuel gauges... I need to know where the feed line to the fuel sender is supposed to end up under the dash in my '74. The needle is pegged all the time, but I know it's not the ground because I've had the tank out, swapped with one from my known good parted out Julius truck... and rebuilt the ground strap/wire. I later found out the feed wire to the sending unit was cut/burned at some point by the previous owner and I can't seem to find the other end anywhere. Seems to be white coming from the tank, but could be a faded other color, I just can't quite tell. If someone knows the pin number and/or wire color off of the back of the cluster I can trace it from that direction. Thanks!

[Just call me Sean]

It says pink or tan.

[bnoon]

Guessing tan on mine as it looks dirty white right now and no hint of pink... It's so hard to tell on these old wires especially when dark outside and lit up with super bright white LED work light. Thanks!!!

[hatzie]

The 1974 GM wiring diagrams are in my signature at the bottom of this post. Download and open with the Free Adobe Acrobat Reader.

If you're rig has one tank...
The sender unit is called "Fuel Meter Tank Unit". You'll find it about halfway up the RH side of the main wiring page.
The firewall is a line on the diagram noted as "Front of Dash". The firewall/bulkhead plugs are near the bottom of that line. You'll need the circuit # to find the terminal position.

The Fuel sender wire is {18T-(GXL)-30}. Translated {18AWG Tan - (Series G Crosslink Polyethylene jacket) - circuit#30}. The "G" in GXL looks like C in these diagrams. It's "G" there is no such thing as CXL Xlink Poly automotive wire. Valid jacket thickness series are TXL, GXL, & SXLfor Xlink Poly primary wire and Xlink Poly Battery cables are SGT, SGR, or SGX.

In the diagrams you'll find circuit 30 at the instrument panel plug and the firewall/bulkhead plug as well as inline with the wire in several places.

Anywhere the wiring has been exposed for the last 40 years I would bet the color has been bleached out of the jacket by the elements. Tan Crosslink Polyethylene probably fades to an eggshell off white.

[dieseldawg142]

why bother trying to find the other end of the wire, if the sender wire is broke outside of the cab, do like i did, replace the sender wire from firewall plug to sender with a new piece. took all of 10 mins & i had my gauge back. it is after all a faded out 40 yr old wire...
if the wire is broke in the cab-start hunting...

[hatzie]

The sender connector is the same as the 1970-1972 Chevelle Wagon sender wire. The Chevelle part is repopped as a complete sender to firewall wire. The molded sender connector will pop right onto your pickup sender. Google "72 Chevelle Wagon Sender wire"

To fit to the bulkhead plug... You'll need to buy a Packard 56 Bulkhead terminal and crimp it onto the replacement sender wire at the firewall end... after you run the replacement wire up from the tank.
I've forgotten whether the engine compartment half of the bulkhead plug is male or female.

• 2965481 is the Delphi Packard 56 series 18 Gauge Male Terminal
• 2965510 is the Delphi Packard 56 series 18 Gauge Female Terminal

You can get terminals from Amazon or from The Electrical Depot or Del-City or...
The HT-11 "W" crimp tool from The Electrical Depot will do an OK job.

[bnoon]

Originally Posted by hatzie

The sender connector is the same as the 1970-1972 Chevelle Wagon sender wire. The Chevelle part is repopped as a complete sender to firewall wire. The molded sender connector will pop right onto your pickup sender. Google "72 Chevelle Wagon Sender wire"

To fit to the bulkhead plug... You'll need to buy a Packard 56 Bulkhead terminal and crimp it onto the replacement sender wire at the firewall end after you run the replacement wire up from the tank.
I've forgotten whether the engine compartment half of the bulkhead plug is male or female.

• 2965481 is the Delphi Packard 56 series 18 Gauge Male Terminal
• 2965510 is the Delphi Packard 56 series 18 Gauge Female Terminal

You can get terminals from Amazon or from The Electrical Depot or Del-City or...
The HT-11 "W" crimp tool from The Electrical Depot will do an OK job.

Thanks for the explanation and links!

Originally Posted by dieseldawg142

why bother trying to find the other end of the wire, if the sender wire is broke outside of the cab, do like i did, replace the sender wire from firewall plug to sender with a new piece. took all of 10 mins & i had my gauge back. it is after all a faded out 40 yr old wire...
if the wire is broke in the cab-start hunting...

Yeah, didn't know where to look in the engine bay for a wire or plug, so I asked. I will be replacing what needs to be replaced for sure.

[bnoon]

So, I found a tan wire coming out of the front bulkhead going to a factory looking female spade enclosed connector. 11.x volts there with key on. Is this my wire?

Wire coming up from the tank shows open when tested to ground. I'm supposed to see resistance there with the amount of resistance dependent upon the amount of gas in the tank, correct? The ground to tank is good, but I'm guessing what's left of the factory wire from the passenger's header back is toast. Thanks guys!

[tucsonjwt]

One option - if you have a pick and pull junkyard in your area which has a truck of your vintage, you can start taking apart that truck's wiring to get a hands on idea. I have used that method rather than hack up my own vehicles looking for a problem.

[bnoon]

Originally Posted by tucsonjwt

One option - if you have a pick and pull junkyard in your area which has a truck of your vintage, you can start taking apart that truck's wiring to get a hands on idea. I have used that method rather than hack up my own vehicles looking for a problem.

Yup, I do that all the time. Now that I know what I'm looking for, I can test resistance and trace wires/etc. I go pretty much every weekend for a few hours just to see what's new. I did a "picture recon" mission the last time I went there not for parts because I couldn't quite remember how this set of power steering and AC brackets went back together since they were different than my last SBC truck (1986).

[midnight rambler]

did you ever fix the problem ?

[Jeepwm69]

When my truck had it pegged to 3 oclock I had a broken wire. Spliced it back together and it's worked fine since.