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Fuel gauge, different readings on run and accessory

canblue

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Nov 16, 2011
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Location
Ontario, Canada
This is driving me nuts. The fuel gauge does not register the amount of fuel correctly. I have an Autometer fuel gauge. I have grounded the the ending unit directly to the -ve battery post. I have rewired the 1969 Coronet with a Mopar setup from Painles. When I turn the ignition switch to ACC, the gauge registers 1/4 tank (tank is full). I then turn the key to run and it reads empty. It is getting 12 volts. The setup doe not use the dash cluster. Jumped the sending unit wire from the sending unit directly to the gauge. Still getting the faulty reading. We did test the sending unit ohms before installing it. The sending unit i about 3 years old, got it with a 1/2 fuel line feed. Any suggetions?
 
i would advised you to take the gage and test it on a known good working sending unit. or drain the tank remove sending unit and bench test. might be cruded/rusted up sitting for 3 years ?
 
Is it possible your ignition switch is dropping some voltage in the lower reading position? Might want to check that also...
 
i would advised you to take the gage and test it on a known good working sending unit. or drain the tank remove sending unit and bench test. might be cruded/rusted up sitting for 3 years ?
Can I remove the sending unit without dropping the tank? We did test the sending unit in an empty tank with the filler tube removed. We moved the float through the empty and full cycle and things were working OK. I may have caused a problem as I was not sure what the full level would be. The cycle that I tested was from the bottom of the tank to the top and I did adjust the float arm. I mention this because I had a problem with a blocked venting system in the tank. I had filled the tank to the point where the pump nozzle stopped the fill. I then went to a car show and the system started leaking near the ending unit. Took the car home and decided to check the fuel level. Well I got a surprise bath of fuel when I took the cap off. Over pressure. Removed enough fuel to be able to take the cap off. Rechecked all of the fuel line clamps. Based on the what I now know, I think that about a half filled tank ( looking at the tank placement and the filler neck ) is equal to a full tank or there is a problem with the tank placement. I replaced the tank with a used one that was suppose to be correct and yes, it was cleaned out. I did run into a problem when installing the tank. The "J" bolt brackets had been removed. I put a piece of flat steel in the trunk for the bolts that held the straps, and used the "J" bolts. So, I am wondering if the tank is not sitting correctly, ie, that rear of the tank is lower than the factory location. I could not find any "J" brackets that did not come in an expensive kit. Limited budget you know. Sorry for the long post, I did try to condense the info. Thanks for all of the suggestions.
 
Can I remove the sending unit without dropping the tank? We did test the sending unit in an empty tank with the filler tube removed. We moved the float through the empty and full cycle and things were working OK. I may have caused a problem as I was not sure what the full level would be. The cycle that I tested was from the bottom of the tank to the top and I did adjust the float arm. I mention this because I had a problem with a blocked venting system in the tank. I had filled the tank to the point where the pump nozzle stopped the fill. I then went to a car show and the system started leaking near the ending unit. Took the car home and decided to check the fuel level. Well I got a surprise bath of fuel when I took the cap off. Over pressure. Removed enough fuel to be able to take the cap off. Rechecked all of the fuel line clamps. Based on the what I now know, I think that about a half filled tank ( looking at the tank placement and the filler neck ) is equal to a full tank or there is a problem with the tank placement. I replaced the tank with a used one that was suppose to be correct and yes, it was cleaned out. I did run into a problem when installing the tank. The "J" bolt brackets had been removed. I put a piece of flat steel in the trunk for the bolts that held the straps, and used the "J" bolts. So, I am wondering if the tank is not sitting correctly, ie, that rear of the tank is lower than the factory location. I could not find any "J" brackets that did not come in an expensive kit. Limited budget you know. Sorry for the long post, I did try to condense the info. Thanks for all of the suggestions.
the sending unit can be removed with the tank in . it will on my 69rr. make sure the fuel level is below the sending unit or you could get a bath .... again. be careful .
 
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