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Need help to troubleshoot gas sending unit

jeryst

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Getting my 74 Challenger ready for the season. Gas gauge does not work. Previous owner said the gauge worked until he had the gas tank replaced. Original sending unit was used with the new tank, so I feel it has to be some type of wiring/grounding issue.

The car currently has almost a full tank of gas. How do you troubleshoot the sending unit? Can it be done with everything still in the car?
 

Challenger RTA

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Check to see if the ground strap is connected good or even there.

groundstrap.jpg


20050106 041.jpg
 
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EW1BH27

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You can put an ohmmeter between the the sending unit's input post (where the blue wire goes) and ground. Since you said you have a full tank the meter should read around 10 ohms. If the float is at the bottom (empty) the ohmmeter will read around 70 ohms.
 

ColoradoCuda

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I just did the resistance check mentioned above, it reads 57 ohms. I think the tank is full, but something is odd with that too. I was driving a couple weeks ago and ran out of gas. I had someone bring me some, and I put in about 2 gallons. Then I went to the gas station and I could only get about 8 more gallons in. Weird. Now I'm going to try to siphon the tank down and remove the sending unit.
 
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