64 Cutlass fuel gauge issues HELP
February 21st, 2013, 03:28 PM
#1
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Location: New York
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64 Cutlass fuel gauge issues HELP
I am new to this forum but I am looking for a little help. The gauge reads empty when the key is turned off but when the key is turned on the gauge spikes above full and doesn't move even when the car is full, half or empty. I was about to drop the tank but was told that it could be an electrical issue also so I am looking for some solutions
February 21st, 2013, 06:02 PM
#3
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Join Date: Jun 2009
Location: southeastern Michigan
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What the gauge does when the key is off means nothing. What it does when the key is on tells you that there is an open in the gauge circuit. The gauge is just an ohm-meter. Zero ohms corresponds to an empty tank, while 90 ohms corresponds to a full tank. The reason it goes way past Full is because an open circuit is infinite ohms, which is much more than 90.
The first thing to do is to verify that your wiring is good. Find the place in the rear of the car where the wire from the sending unit (often orange in color) connects to the wire coming from the gauge. This is usually in the area behind the rear license plate or maybe in the trunk behind the latch area where the wiring for the taillights passes across the rear of the trunk.
Pull the connector apart and ground the side coming from the gauge. Then put the key in the ON position, and the gauge should go to Empty. By grounding this wire, you are making the resistance zero.
Removing the wire from ground with the key still on should make the gauge go past Full, like it's been doing. If the gauge does this, then you know the gauge itself is ok.
Before dropping the tank, though, the next thing to do is verify that the other wire coming from the sending unit, the ground wire, which is black, is actually connected to ground and that that ground is good. This connection is usually made forward of the tank up under the body behind the axle, and you may have to crawl pretty far under the rear of the car to find it. Make sure that the connection is clean as this is an area where lots of crud can build up along with corrosion.
If the ground is verified to be OK, then your next step is the dreaded dropping of the tank to get at the sending unit. But do these other checks first as they're much easier repairs than dropping the tank, so you don't want to have to drop the tank until you've eliminated everything else.
The first thing to do is to verify that your wiring is good. Find the place in the rear of the car where the wire from the sending unit (often orange in color) connects to the wire coming from the gauge. This is usually in the area behind the rear license plate or maybe in the trunk behind the latch area where the wiring for the taillights passes across the rear of the trunk.
Pull the connector apart and ground the side coming from the gauge. Then put the key in the ON position, and the gauge should go to Empty. By grounding this wire, you are making the resistance zero.
Removing the wire from ground with the key still on should make the gauge go past Full, like it's been doing. If the gauge does this, then you know the gauge itself is ok.
Before dropping the tank, though, the next thing to do is verify that the other wire coming from the sending unit, the ground wire, which is black, is actually connected to ground and that that ground is good. This connection is usually made forward of the tank up under the body behind the axle, and you may have to crawl pretty far under the rear of the car to find it. Make sure that the connection is clean as this is an area where lots of crud can build up along with corrosion.
If the ground is verified to be OK, then your next step is the dreaded dropping of the tank to get at the sending unit. But do these other checks first as they're much easier repairs than dropping the tank, so you don't want to have to drop the tank until you've eliminated everything else.
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