mdeslyper

1976 coupe.

Was wondering how long it should typically take for a gas guage to register a full tank. The sending unit is new. When I fill the car up it has been taking 10miles + to show a full tank. Seems like a long time. What is normal? Is the guage on it's last legs?

Mike

mdeslyper

Thanks for info Alan - it definitely does not work like that.

7T1vette

Does it act like Alan71 described, but take longer time to do so? If so, it could be an aftermarket gauge that has a different damping oil in the meter than the factory installed. If a regular type of oil was used (thicker viscosity), it might take much longer to stabilize. But, 10 miles driving to get it to read full is very unusual.

mdeslyper

It very slowly creeps up - hard to see the movement. Eventually makes it to full - but takes a long time. Should it go up at the gas station with the key out of the ignition? Or does key need to be in the on position? It has been very cold lately (30deg) would that have an effect?

MelWff

Before the previous sending unit failed, did it take a long time for the gauge to register? If not I would suspect the quality of the new sender.

bj1k

That would be an obvious conclusion and considering the low quality of most parts today I would surely suspect the fuel sender. Sometimes when an old sender does that it just needs cleaned with a fuel system cleaner to remove the calcium deposits . The C5 Corvettes are known for this trouble and adding a bottle of Techron will usually cure the problem.

mdeslyper

I had my tank out for other reasons. Suspected the sock on the pick up tube had clogged so when I had the tank out, I restored it all with new parts. This slow guage issue seems like a new development. I did the tank restore and new sender several years ago. I will have the interior out later this year and was curious if a deteriorating guage could be the culprit.

maverickmk

I replaced a sending unit in my daughters car with a cheap part and when it's full it's reads empty, then as you drive it a few miles it starts to read full. I believe that the problem is that the float is not calibrated correctly and when the tank is full it goes too high to send a correct signal to the gauge.
Look at this picture and notice the lines in a semi-circle. As the float moves up & down it makes contact with these lines, known as a rheostat. This changes the amount of resistance in the ground circuit which allows more or less current to flow through the gauge causing the needle to move.

mdeslyper

Thanks for the pic - it is nice to see how things work.

0Willcox Corvette

One way to eliminate the dash unit.. pull the ohms wire off the tank... turn the key on.

What you will see is a full tank and it should go there pretty quick.. This is also how the gauge should function with a full tank and the wire hooked up. Next ground out the ohms wire and see if the gauge goes to empty (again pretty quick). There will be some delay but not much.

If the dash unit pass's this test then I would suspect the sender is your issue.

If you watch this video you'll see exactly how your gauge should respond. This is the same for all dash fuel gauges 1968-1982.


Willcox