I recently installed a new gas tank and sending unit in my '66 Monza. The fuel gauge works now, but is not accurate.

The needle doesn't move off of empty until five gallons are in the tank.

Then when the tank is completely full, the gauge reads 3/4 full.

The range from the full position to the empty position is only 7.5 gallons.

I suspect that my new sending unit is at fault, but I wanted to check with the forum experts before I order a replacement.

I recently put a new tank and sending unit in my 66 also and discovered three things:
It seems most floats on new senders are installed backwards for a Corvair. The long side of the float should be toward the center of the tank so they don't rest against the tank wall.
The floats tend to leak.
Some of the sending units are bad out of the box.
My gauge stayed on empty after filling the tank. I pulled it after burning most of the gas off and found the float backward and full of gas and a bad sending unit. The supplier replaced the sender and I installed a Ford float. Someone posted the part number here. All is well now.

Brice

66 Corsa Turbo Convertible

Bozeman, Montana

I installed a new Clark's sender and the float was turned backwards. I know the senders are new but I wire them up and ops check them before installing them in the tank.

1964 Monza Coupe
1965 Corsa 140
1967 Monza Coupe

Maryville, TN
U.S. 129 The"Tail Of The Dragon"

Factory "setting" for the sender for our 14 gallon tank is to show Empty when 9 gallons are used..

Easy to just bend the rod to lower the Float in relation to the sending unit so there will be only one or two gal. left..

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Thanks. Theoretically, bending the rod down should also help the needle move all the way to "full." Right?

I'll give it a try. I'll also verify that the float is not in backward.

Make sure you don't have an early model sending unit...different resistance. Testing it out of the tank is best! ...stop to stop