Fuel gauge still not working, What am I missing? |
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Fuel gauge still not working, What am I missing? |
john77 |
Mar 27 2014, 02:24 AM
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#1
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Senior Member Group: Members Posts: 621 Joined: 21-February 14 From: Los Angeles Member No.: 17,027 Region Association: Southern California |
With the ignition on the needle on the gauge lifts to E but goes no further despite the tank being full.
I pulled the sender, wired up a new ground and hooked up a new wire from the gauge to the sender and tested the sender manually by turning it upside down and then back. The needle goes from empty to full and back to empty. Just to double check I test the resistance, 0.2 ohms right side up, 89.9 ohms upside down (the range is 0-90 ohms). So I put the sender back in the tank with the new wiring, switch on the ignition and... the needle rises to E and goes no further. So I think maybe, somehow, the floats not lifting. So I pull the sender, fill a bucket of water, dip it in, and the needle on the gauge rises and tells me I have half a tank - or less or more depending how much I submerge it. In other words, the damn thing is working. So I put it back in the tank and nothing, the gauge rises to E and stays!!! What the hell am I missing here? It works in a bucket of water but move it a foot and put it in my gas tank and nothing. John |
stugray |
Mar 28 2014, 06:05 PM
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#2
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Advanced Member Group: Members Posts: 3,825 Joined: 17-September 09 From: Longmont, CO Member No.: 10,819 Region Association: None |
I will try again:
"I pulled the sender, wired up a new ground and hooked up a new wire from the gauge to the sender and tested the sender manually by turning it upside down and then back. " If you can turn the sender upside down and have it change resistance, then it is not a capacitive type sender. So: "Just learned the dialectric constant of water is way higher than gas, so my water test was pointless.. who knew " This should not matter. You can make it work in the water, but not in the car (gasoline). SO when you put it in the car, you are somehow shorting out the sender unit. Try swapping the wires on the sender unit. One of them is probably grounded to the sender case. The other is the variable resistance. If it is hooked up backwards, it will work in the water, but not in the car. |
john77 |
Mar 28 2014, 07:07 PM
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#3
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Senior Member Group: Members Posts: 621 Joined: 21-February 14 From: Los Angeles Member No.: 17,027 Region Association: Southern California |
I will try again: "I pulled the sender, wired up a new ground and hooked up a new wire from the gauge to the sender and tested the sender manually by turning it upside down and then back. " If you can turn the sender upside down and have it change resistance, then it is not a capacitive type sender. So: "Just learned the dialectric constant of water is way higher than gas, so my water test was pointless.. who knew " This should not matter. You can make it work in the water, but not in the car (gasoline). SO when you put it in the car, you are somehow shorting out the sender unit. Try swapping the wires on the sender unit. One of them is probably grounded to the sender case. The other is the variable resistance. If it is hooked up backwards, it will work in the water, but not in the car. Sorry Stu, I keep checking back on this on my phone and completely missed your first reply. The sender is an aluminum shaft with a float inside it that appears to run up and down a circuit board. This is the unit: http://www.fuelsafe.com/store/sending-unit...oline-only.html Maybe I'm misunderstanding how the sender works, but when I put it in a bucket of water the ground terminal on top of the sender was wired to a ground on the chassis. Isn't that how it grounds? The shaft doesn't seem to touch the tank - it's smaller than the hole, the top of the sender is plastic, and there's a gasket between it and the tank. When I asked the guy from Fuel Safe if the sender touching the metal of the tank would be a problem he said: "The outside aluminum shell or shaft of our standard senders is grounded so touching the side will not hurt anything as long as the ground wire is on the correct lug or terminal. The ground will have a G by it." I tried swapping the wires into the sender as you said and now the needle has gone all the way over as far as it can and has stayed there, even with the ignition off. If I swap the wires back on the sender it makes no difference, the needle just stays there. |
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