TR6 Need Help With Fuel Gauge

[Smitty9006]

Hello,
I’ve stated a thread on The Triumph Experience and received lots of feedback, Unfortunately, I haven’t solved the problem with my fuel gauge not working and I feel like I’ve exhausted the topic there. My car is a 1975 with 7k miles so the wiring harness is original. Let me get you up to date with my issue of the fuel gauge not working. I’ve replaced the sending unit and voltage stabilizer. The gauge reads full if I ground the green sending unit wire. Doesn’t that mean that the gauge is not broken? The temp gauge works fine. I’ve heard that they get power from the same source. The fuse is good. I suspect the problem is with the fuel gauge ground. I tried tracing the sending unit ground by feeling the wiring and part of it goes back to the rear left tail light. Back there, two wires are not connected to anything and I don’t see any empty connection points- see pictures. I don’t know if it’s related but the rear blinkers illuminate but don’t blink. Getting back to the fuel gauge, where is it grounded? Is it in the engine bay? My car has a/c so getting behind the gauge is really nearly impossible. I’m hoping that it’s a simple, easily accessible ground wire problem. All help is greatly appreciated.

 

[charleyf]

The 2 wires you show in your first Pic are black. That means they are ground wires. They do not necessarily need a place to go but if they are within reach of something like your fuel gauge sending unit that would be highly suspect of belonging there.
Is there a ground wire coming off of the sending unit on top of the fuel tank? There should be.
It is also advisable by folks who understand these things that, you should also have a ground on the casing of your fuel gauge.
The body of your car is your ground source. So find a place or bolt that is unpainted/ bare and attach the ground wire there.
Your problem is that you do not know if the 2 black wires are leading a ground to something or looking to ground something on the other end. You need to test those wires to determine which way they are intended.
Charley

 

[CJD]

+1
That connector should go somewhere, and not just loose. Find that and you are on your way to figuring this out. Also...what exactly does your fuel gage do?

 

[Stevenry]

When I thought my fuel gauge was about to die, I got it working by reaching up and tightening the knurled nut on the bracket holding the fuel gauge to the back of the dash. I assumed it fixed the gauge ground, but didn’t investigate further because it was working. And still is several years later.

Steve
55 TR2

 

[CJD]

That's always the rule with British cars...if something doesn't work right, it's the ground!

 

[Smitty9006]

Thanks everyone. I’ll attach the black ground wires that are near the left tail lamp. I held it to a ground spot but it didn’t seem to change anything but I’ll still attach it permanently. The fuel gauge shows empty. I grounded the green sending unit wire and it went to full. There is an attached ground wire at the sending unit. I guess I’ll have to get at the back of the gauge but with a/c, it’s a pain.
Thanks again everyone.

 

[Gliderman8]

If you’re fuel gauge is reading empty and you know the gauge works, I would investigate to see if the plastic float on the sender is full of gas. I had the same thing happen to me and I replaced the plastic float with a brass one and that solved the problem.
Edit…. I just saw that you replaced the sending unit so it shouldn’t be the float.

 

[CJD]

The fact it has 2 wires tells you that it is not to go to ground, but to be used to ground something. You can check with an ohm meter wires to ground, but I bet they are grounded in the harness and meant to ground something around the taillight.

 

[Gliderman8]

Why not just run a temporary ground wire to the sender and see if the gauge works?

 

[Smitty9006]

Why not just run a temporary ground wire to the sender and see if the gauge works?

I’ll try that. Thanks.

 

[Smitty9006]

Hi All,

It’s working!

I’m not sure exactly what fixed it but I did connect those ground wires to the turn signal ground.

I removed the gauge and broke the bulb. It’s always something…

Thank you all that contributed to this thread. What a great group.

Full disclosure, I’m going to post the same thing on Triumph Experience.