[Jazzbass]

It's funny - I have this exact same problem. Have for years. Fill up and gauge is stuck at 3/4. Probably about 6 years ago I just assumed it was the sender and replaced it. Same problem. An ohm meter on the old gauge and the new shows it reading correctly if you move the float up and down.

I'll admit I've been too distracted with other things to think about it much, but there are a couple possibilities:

1. The gauge itself it hosed.
2. The wiring is messed up. More likely a problem on my car with it's 1950s style wiring loom than yours, Richard.
3. For some reason the float gets "stuck" in the car. Doesn't really make sense given that it happens multiple senders.

I'll break out the ohm meter this evening and see if I can make any discoveries.

[Vicegrip]

Bring it over....

[heliolps2]

Hi Richard it's Helio,

it's been a while, I still live near by Vienna and I own 92 C2 Turbo for a while now, you should come by and visit, I would swap out my fuel gauge for testing, I have all the tools we need at my place, Email me at heliolopes@greatgatherings,comand I'll give my number and address and I happy to help anyone that owns a 964, 964 Turbo and 930 setups, for free.

Helio

[Richard Curtis]

helio, good to hear from you. PM sent. --richard

[Richard Curtis]

Compared my fuel gauge reading to Helio's (extremely beautiful) 964 Turbo's and the readings were identical: Full. Previously, I had been incorrect and confused in thinking the tank was full ... that's was a long time ago. This past weekend, the gauge reading went from slightly more than a quarter tank to full when I refueled it with 13 gallons of gas. Next up: drive the car enough to cause a different reading.

[Richard Curtis]

fuel gauge now works. although i tried several things, i believe it was the installation of a new OEM fuel sender ultimately that solved the problem of erratic readings. In the process, i did clean a lot of electrical connections, grounds, etc.

[Vicegrip]

Yea! If you like bring it by and we can clean up the wiring to the sender a bit.

[Jazzbass]

Originally Posted by Jazzbass

It's funny - I have this exact same problem. Have for years. Fill up and gauge is stuck at 3/4. Probably about 6 years ago I just assumed it was the sender and replaced it. Same problem. An ohm meter on the old gauge and the new shows it reading correctly if you move the float up and down.

I'll admit I've been too distracted with other things to think about it much, but there are a couple possibilities:

1. The gauge itself it hosed.
2. The wiring is messed up. More likely a problem on my car with it's 1950s style wiring loom than yours, Richard.
3. For some reason the float gets "stuck" in the car. Doesn't really make sense given that it happens multiple senders.

I'll break out the ohm meter this evening and see if I can make any discoveries.

So I fixed my fuel gauge problem this past weekend. Keep in mind this is for an 85, so early body/fuel tank style, not a 964 like in Richard's original post. This is important.

The problem? The top of the fuel tank was dented, right here:



Pretty easy to understand why, as I spent many years tossing very heavy track boxes on top of the tank in the trunk.

The fuel level sender goes in near the rear of the tank. At the bottom rear of the tank is a small hump where the tank goes over the steering rack. When everything is in line (not dented), the sender goes straight down and just barely clears the hump, going just in front of it:


(Red line here is the depth of the fuel level sender)

When the top of the tank gets dented, it angles the fuel sender back towards the hump. Now the sender either can't go in all the way or (in my case) gets pushed into the hump and kinked:



Here's the sender I pulled out - you can see the top is no longer at a right angle with the body, which is critical for the float inside to move up and down freely:



It also explains why I could never understand what was the problem. I'd pull the sender out, it would straighten out in the process, and the float would free up and all the resistance reading would be correct. Put the sender back in the tank, it'd get kinked again and stop working. Buy a new sender, put it in, same problem as before.

I used a wooden dowel to bend the dent out of the tank, reinserted the sender and for the first time in like 10 years actually knew how much gas I had in the car.

[VaSteve]

Wow that's nuts. Nice fix.

[Richard Curtis]

the new sender (2nd or 3rd one) fixed the problem. Kurt was a big help, of course.