# 64' Fuel Gauge Troubleshooting



## Benryanuk (10 mo ago)

The fuel gauge on my 64' GTO only reads empty (has never worked since I've owned the car), so I've been spending time troubleshooting this week.. grounding the sender wire at the tank makes no difference and likewise grounding the sender wire at the gauge. Any further tips? I suspect it's the gauge, but I've not had much luck finding a replacement yet -- any help would be much appreciated! thanks, Ben


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## gto4ben (May 27, 2018)

I believe grounding the sender is supposed to read empty. You may have the opposite problem - no voltage to the gas gauge. I bench tested my gas gauge for my '67 GTO as shown below. Empty sender voltage reads 0.646V (zero ohms to ground) and Full sender voltage reads 7.36V (90 ohms to ground) over the full float travel. Supply voltage was around 14V. Yours should be similar.

Check if you're getting 12V on the brown wire on the back of the gas gauge. If so, loose/dirty 12V connection to the gauge is suspect. There are nuts holding down a shunt resistor. Inspect the nuts for corrosion and check this resistor for breaks. The Gauge also needs have a good ground to the back of the instrument cluster. I've attached the '64 GTO wiring diagram and rear photo's of my '67 GTO Standard and Rally gas gauges to help your troubleshooting effort.


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## GtoFM (Mar 23, 2018)

2 things. The gauge needle looks to be stuck on the trim plate over the gauge, or is that an illusion? Also FYI, the '64 sending unit is 0-30 ohms. It was changed to 0-90 ohms in '65.


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## Benryanuk (10 mo ago)

Thank you, this is very helpful and I appreciate you taking the time to reply -- I'll report back.



gto4ben said:


> I believe grounding the sender is supposed to read empty. You may have the opposite problem - no voltage to the gas gauge. I bench tested my gas gauge for my '67 GTO as shown below. Empty sender voltage reads 0.646V (zero ohms to ground) and Full sender voltage reads 7.36V (90 ohms to ground) over the full float travel. Supply voltage was around 14V. Yours should be similar.
> 
> Check if you're getting 12V on the brown wire on the back of the gas gauge. If so, loose/dirty 12V connection to the gauge is suspect. There are nuts holding down a shunt resistor. Inspect the nuts for corrosion and check this resistor for breaks. The Gauge also needs have a good ground to the back of the instrument cluster. I've attached the '64 GTO wiring diagram and rear photo's of my '67 GTO Standard and Rally gas gauges to help your troubleshooting effort.
> View attachment 152887
> ...


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