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Fuel sender, fuel gauge 100 4

Jerry

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I was helping a friend with his 100 4. The fuel gauge just came back from Nosinger gauge repair. Looks beautiful. I hooked the unit up with the correct wires as per the wire chart and the needle went to full right away. The tank is about full , but this was so fast I am wondering if there is an issue. I have asked the owner to siphon out gas to see if it changes the needle but I also have a quesiton:
I noticed there was seepage around the sender unit in the tank. He ordered a new gasket for that. But, typically when there is seepage, there is also gas within the coil area. Will that affect the reading?
PS: I did put an extra ground to the sender since the fuel line had been cut going to the coil and rubber hose put in which would have killed the ground in that direction.

Jerry
 

steveg

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Left, my tank sender currently. The wet stuff is 11-year-old hylomar. No gas leakage after 11 years.
Current sender is OEM unit, installed Nov 2006. I replaced the original phillips screws with panheads to further spread the pressure.
Right, original Moss repro sender install, May 2005. Washers are Dorman bonded sealing washers.

PS - since you have a ground wire, suggest pulling the sender out and operating the arm by hand to make sure the gauge follows it.
If nothing happens to the gauge, it's either wired wrong at the gauge or the little internal wire to the gauge wire post may have been broken.
PPS - make sure the float arm points toward the front of the car.
It's normal for the sender unit to be filled with gas.
TankSender1117.jpg
TankSenderCloseup0505.jpg
 
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Jerry

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I think we need to pull it and test it then. Have to change the gasket anyway. Thanks Steve.

Jerry
 
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Jerry--

I've had the best results in stopping leaks at the sender by installing a new cork gasket.

When you are doing your testing of the sender the needle should of course change as you move the arm up/down. Though some have figured a way to dampen the sender's signal with a resistor or some other component to make it less jiggly the odometer should give you an acceptable indication of the amount of fuel remaining. My car's mpg is a consistent 23-25 and at 200 miles I am looking for a gas station. at 250 looking hard!
 

dklawson

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I hooked the unit up with the correct wires as per the wire chart and the needle went to full right away.

A 100-4 would be old enough to have the magnetic gauge system. It's fuel gauge should snap immediately to whatever reading is appropriate as soon as the ignition key is turned to run. That would be normal.

You can confirm (more or less) normal gauge function by jumpering to ground the "T" terminal on the back of the gauge. That should peg the needle at/below the Empty marker. Remove the jumper and the green/black wire from the sender and the gauge should go to (or above) the Full marker.
 
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... I've had the best results in stopping leaks at the sender by installing a new cork gasket. ...!

Sometimes, the flange on the sender is warped due to a DPO cranking down on the screws in order to stop a leak. And aftermarket tanks might not have a perfectly flat flange either. I solved this problem on our BN2 by stacking two cork gaskets with a THIN film of fuel-resistant sealant--Permatex makes one--on all surfaces. You'll need longer screws.
 
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Jerry

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Thanks for the help group. I will inform the owner of your recommendations and we will get it fixed!
 
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