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Fuel gauge and sending unit

1K views 2 replies 3 participants last post by  Irelands child 
#1 ·
I'm doing a 65 Ranchero. Have gauge pod from 66 'Stang and added gauges in lieu of all "idiot" lights. I tried using the original fuel sending unit but could not get a reading on the gauge. I ordered a new sending unit and installed same. Still no reading on the gauge. I checked with the manufacturer and the sending unit is supposed to be calibrated for the same resistance in the line as original. I can get a reading at the gauge if I disconnect the line and use a test light grounded to the body. I get a test light and the gauge shows half full. Coincidentally, I actually have about half a tank of gas in the tank but the wire is not connected to the tank sending unit during my test. :) Could it be that the tank is not actually grounded to the body of the car? I believe the sending unit is supposed to be "self" grounded when installed in the tank. Is either of those correct, incorrect assumptions on my part? Any help would be greatly appreciated. I have a very good multi tester but am not learned enough to know how to use/interpret the readings I may get in any attempt to test the sending unit with it. Thanks. bwinnett
 
#3 ·
It has been a while since I've worked on this vintage Ford, but my recollection (and this kind of information is fading fast ??)is that the gas level sender is held in place with a cam lock rather then several screws. That lock is pretty well insulated with a gasket/seal from the tank. I would try adding a separate ground. Also, on many Fords, there is a little ~1" metal device buried somewhere high up and behind the dash called a positive voltage regulator. They control and maintain some level of voltage to the gauges. Usually when they fail, the gas gauge goes full scale - but there are exceptions to any 'rule'. Then there is always that bug-a-boo, a bad gas tank level sender or the incorrect ohm output
 
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