1969 Fuel Gauge Stuck? - Chevelle Tech
Electrical & Wiring Troubleshooting electrical problems.

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post #1 of 5 (permalink) Old Oct 2nd, 17, 2:06 PM Thread Starter
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1969 Fuel Gauge Stuck?

I've read several threads on this, but sorry, can't seem to get my arms around this?
My gauge worked fine until the last couple weeks. Works fine from Full to a tick under half and tracks perfectly - then nothing my last 6-7 gallons?
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post #2 of 5 (permalink) Old Oct 2nd, 17, 5:45 PM
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Re: 1969 Fuel Gauge Stuck?

Likely your sender is worn out. It varies resistance as the float drops from 90 ohms at full down to zero at empty. You can pull the wires at the dash and measure the resistance to ground of the one going back to the tank. If it's not dropping lower than about 45 ohms, then that is why your needle remains at 1/2. If it is, it could be your guage. Mine did the same thing. There is a wiper on a coil of wire at the sender. That coil of wire had worn through. Drop your tank and have a look.
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post #3 of 5 (permalink) Old Oct 2nd, 17, 7:08 PM
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Re: 1969 Fuel Gauge Stuck?

If you remove the wire to the sender with the key on, your gauge will drive past full. If you ground that same wire the gauge will go to empty. If both of these things happen then your sender is no good.

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post #4 of 5 (permalink) Old Oct 7th, 17, 10:03 PM
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Re: 1969 Fuel Gauge Stuck?

To expand on what oldcutlass stated, this can give a false positive test. Granted the gauge with the ignition switch on and then grounding the sender wire in the trunk should make the gauge go to empty and then when ungrounded should have it going to full, you can also get the same results if the gauge has a defective shunt resistor on it.

Here are some tests I did on a 67 Impala gauge that is designed to work with a 0-90 ohm sender:

You can see how the gauge is thrown off without the shunt.

Ideally do some tests at the trunk connection to verify things before replacing the sender in the tank that might be good but instead you may have a gauge shunt issue.

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post #5 of 5 (permalink) Old Aug 13th, 18, 9:22 AM Thread Starter
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Re: 1969 Fuel Gauge Stuck?

Hi All;
Finally back to this issue. I've checked the gauge only from the connection in the trunk (grounded and ran to empty - removed wire ran to full, etc.) With that appearing to work correctly - I filled the tank and have been driving the gas out of it this week. Jostling the trunk around every time I returned home, I believe I loosened the sending unit in the tank to start working again. It's been tracking on it's way down from about 5/8.

Here's the weird thing. I ran the car out of gas the first week I had it - and gauge read 1/4 when it ran out. So when I got to gas station - I filled up - and the tank only took just over 12 gallons? It's a replacement tank. Can a 12 gallon tank exist? It's a new tank with a new sending unit.

This leads to another problem, I'm pretty sure I'm going to run out of gas in the next day or two right around 1/4 tank ( I have a gas can in trunk this time!). But all the OHM readings are spot on for where the gauge reads now (5/16 full gas - ohms are 29.0)

So if I run out the tank at 22.5 ohms, what's my options to get gauge closer to reality?

Thanks for your thoughts on this!
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