| 46coupe | -- 04-30-2017 @ 3:53 PM |
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Hello again, Took the car out for a spin today and the gas gauge pegged past the full mark. As several of you are aware we just solved the metal noise problem in the tank. I reinstalled the new sending unit, hooked up the wires in their original location and hooked up the battery about 3 days ago. The gauge moved so I figured that everything was ok. Today the problem arose. Could the problem be with the sending unit or possibly electrical? Everything worked ok prior to our search in the tank for the metal noise a week ago. Appreciate any help or ideas, as usual.
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| TomO | -- 05-01-2017 @ 7:21 AM |
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As my first swag, I would look to see if the sending unit screw is grounding out on the cover. I have a piece of electrical tape on the cover where it might contact the sending unit screw that secures the wire. Fix this before you drive the car as you can damage the gauge by leaving the sending unit wire grounded for an extended period of time. Tom
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| 40cpe | -- 05-01-2017 @ 7:26 AM |
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It sounds like the wire to the gauge or the sender is shorted. Remove the wire from the sender and see if the gauge moves. It might be, though unlikely, that the sender is fouled or stuck in the "full" position. Edit: TomO posted as I was typing. This message was edited by 40cpe on 5-1-17 @ 7:27 AM
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| len47merc | -- 05-01-2017 @ 7:39 AM |
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Just a thought - did you replace the ORIGINAL sending unit? Many of the new replacement units have a ground wire that needs to be attached to the frame, whereas the originals with the cork floats did not have this (at least on the vehicles I am familiar with). Did the new unit have this grounding wire and is it solidly attached to exposed metal on the frame? Also, did the new unit come with a pre-set float arm or was it a universal model that you had to cut-and-bend to fit your specific application? EDIT - when replacing my original the gauge now buries well beyond full when the tank is filled and it takes 120-150 miles (city-highway) before it passes the full mark, then the full range from full-to-empty is another 100 miles. Clearly I need to re-adjust the arm to a shorter configuration than the instructions that came with the unit directed but I'm living with it as is for the time being. Hopefully your issue is something as simple as one of the above. Steve This message was edited by len47merc on 5-1-17 @ 7:44 AM
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| 46coupe | -- 05-01-2017 @ 5:34 PM |
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Thanks for the tips and comments. I'll be doing some troubleshooting tomorrow and will let y'all know what I find. UPDATE: I noticed that the small fiber washer was missing where the screw is fastened to the unit. I installed a small rubber washer and now the gauge goes a little below the full mark which I think is right. That test was made with the car off and the switch on. Only the battery running the gauge. Would the generator recharging the battery have any effect? I only ask as when driving the other day the gauge climbed more after its initial stop at the full mark. This message was edited by 46coupe on 5-4-17 @ 12:41 PM
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| 46coupe | -- 05-04-2017 @ 12:39 PM |
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UPDATE: I noticed that the small fiber washer was missing where the screw is fastened to the unit. I installed a small rubber washer and now the gauge goes a little below the full mark which I think is right. That test was made with the car off and the switch on. Only the battery running the gauge. Would the generator recharging the battery have any effect? I only ask as when driving the other day the gauge climbed more after its initial stop at the full mark.
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| silverchief | -- 05-04-2017 @ 3:39 PM |
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My gas gauge in my 46 also buries above the full mark, and with ignition off, retreats to just barely above empty. Per one readers suggestion that the sender wire or wire from ignition switch may be shorted - I am showing 2 1/2 volts at the sending unit with ignition off. Should that be? I have a newly installed wiring harness, no accessories other than heater, radio, and clock (disconnected) and have been searching for a drain. Could it be the gas gauge wiring?
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| TomO | -- 05-05-2017 @ 8:08 AM |
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Bill, the sending unit gets its voltage from the gauge. When the ignition switch is off, there should be no voltage supplied to the gauges. The voltage to the gas gauge should come in on the wire that attaches to the passenger side of the gauge. Tom
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| silverchief | -- 05-05-2017 @ 3:03 PM |
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Thanks Tom, Looking at my diagram I see the sender wire goes through two connectors before reaching the gas guage, which receives it's power from the ignition switch - a very short distance away. I hate to think the short would be in that wire, because I have a new harness throughout the car. I'll have it on a lift next week and will take a close look at that sender wire from the tank unit to where it enters the dash. I pulled the ignition switch and everything looks clean and tight. This has to be the mysterious drain I have been plagued with for so long.
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