My experience changing out gas tank sending units has been to take the time to do a little measuring to see where the float sits in the empty position. It usually only takes a couple of minor bends to the rod to get it so the bottom of the float sits between 1/8 and 1/4 inch off the bottom of the tank. Doing this we’ve always gotten accurate gauge readings — better than new.
I should also mention that we often bypass the points-based volage device on the instrument panel and run a solid state device (smooth waveform) of exactly 5 volts in its place. This provides steady and consistent readings for the fuel quantity and water temp gauges that rely on this proper gauge voltage.
The last part of getting one’s fuel supply reliably to the engine is to stay away from gasoline with ethanol in it. We are fortunate to have ethanol-free gas at a number of locations in WA. Ethanol in gas has repeatedly caused us premature failure of tank sending units, fuel pumps, and carburetors. And don’t forget to replace all the connecting bits of hose with the ethanol resistant variety. You have to personally bird dog this, because the guys behind the parts counters won’t look at the SAE numbers printed on the hose. There’s still hose out there that will get you in trouble with ethanol.
If you’re fastidious about the care and feeding of every bit of the fuel supply circuit from tank to carb, you’ll avoid further maintenance issues.
Dan in Seattle
I can't remember if the sender has higher resistance at full or empty. If higher at full with a lot of fiddling around with some resistors or maybe with a variable rheostat you could get it set to read correctly towards empty. But it could be fussy. I guess the easiest way would be to put a known quantity in the tank like 2 gallons and then try to get it adjusted to read correctly.
Paul L.
On Sunday, April 9, 2017 at 12:20:51 AM UTC-5, MO wrote:
64 Dodge B body. I installed a new stainless steel 3/8" gas sending unit and a new aftermarket gas gauge in the correct Ohm range.
When the tank is full. the gauge reads full for about 50 miles, before the needle starts to move. When the needle gets to " empty" there is still about 5 gallons of gas left.
That is not all bad, but what can I do to get it a little more accurate? ......................................MO
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