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Just took the '77 out for the first run of the season. Ran great except the fuel gauge isn't working. It reads empty even though the tank is full. Worked fine when I put the car away 4 months ago. This happened last year for short time but suddenly it started functioning properly and worked through the end of the season.
I guess I should start by checking fuses and grounds.
Is there a fuel gauge circuit fuse in the fuse panel under the dash? Is there a diagram available that would show which fuse it is?
Where is the fuel sending unit grounded to the chassis?
On my 77 I had to drop tank to replace leaky rubber lines. The ground was on top if the tank. It was attached to some flimsy part and broke. I spliced and ran ground tie left rear side. Gas tank pain in butt to drop!
Thanks, I've had the tank out a couple of times. I'll try to get a look at the top of the tank but doesn't the ground get attached to the chassis somewhere?
Yes drivers side by exhaust clamp area by quarter panel. I would take a picture but won't be back home for 2 weeks. There is a connection up top of tank then routes to area I was talking about. When I replaced rubber fuel lines I broke the connection off and I remember splicing wire and running it down to rear driver side. Been a while sorry can't remember details . keYep me posted on your 77 . hope we can help each other out same years.
Last edited by my04heritage; Apr 24, 2018 at 03:29 PM.
Yes drivers side by exhaust clamp area by quarter panel. I would take a picture but won't be back home for 2 weeks. There is a connection up top of tank then routes to area I was talking about. When I replaced rubber fuel lines I broke the connection off and I remember splicing wire and running it down to rear driver side. Been a while sorry can't remember details . keYep me posted on your 77 . hope we can help each other out same years.
Thanks very much. I'm going to take a look first chance I get.
1. faulty sending unit;
2. shorted sending wire (since it happened 'some' last year, this is my pick for the cause of your problem);
3. defective gauge;
4. no power getting to sending unit/gauge.
Check the sending unit wire under the back end of the car. If you see that it may have been (or still is) rubbing on a metal piece, see if the insulation has been rubbed thru.
Second choice is the sending unit. But before you mess with your tank, just hook an ohmmeter up to the sending unit (signal wire to +; chassis ground to -). If you are reading something between 20 and 100 ohms, your sending unit is likely OK.
Last edited by 7T1vette; Apr 24, 2018 at 06:16 PM.
Thanks, I'll take a good look at the sending wire while I'm under there looking at the ground. The issue now is that the gauge just started working again. It's truly intermittent. If there's nothing obvious visually I'll have to wait until it happens again to do any testing.
OK, all this was such good info I had to go in and take a look. Here's what I found, with photos in case anyone is wondering what it looks like.
This connector with sending wire and ground and one nasty looking ground location. That strap attached at the ground goes up to the radio antennae.
Here's the connector with tan sending wire and black ground wire in and out.
Here's the corroded ground attach location.
I unplugged the connector, it looked fine inside. No obvious damage to either wire as far as I could follow them. They both go into a wrapped harness to exit the under fender area. Removed and cleaned up the ground location. Gauge is still woking, crossing my fingers that I won't have any more issues.
If the ground was not making connection... or making intermittent connection... that would result in having no power to the fuel gauge system. Result: reading empty
Fuel Gauge Reads Empty
