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fuel guage

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FULL gas guage is allways on high, help,
on the big rebuild i put a new sender unit in the tank and on the first outing every thing was cool.
Now whatever amount of gas i have in my tank the needle is on full.. I,ve put in a second hand petrol guage in the dash and changed over the voltage limiter, and the tank is earthed in the boot! whoops! I mean trunk.
help please, maybe the sender has gone again?
sick of carrying a can in the trunk.

65,289,C4, lemans red
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You have a short in the wiring to ground somewhere between the gauge and the fuel tank. Remove the wire from the gauge and attach an ohmeter between it and chassis for a good ground - (also remove the wire from the tank sending unit). Trace back wiring until you find area of short.

Three possible causes:
- sticking/faulty gauge;
- sticking float;
- shorted wire.

Disconnect the wiring from the fuel gauge and see if it drops. If it does, the gauge is probably OK.

Check the wiring. Use a multimeter to measure the resistance (Ohm-setting) between chassis and wire (disconnect wire at both ends first). If you read a very low resistance (a few ohms) there is a short.

Check the float/sender unit. Take it out of the petrol tank (yes, I use BE), connect the wire to the plug and a metal part to the car. Move the float up and down. The fuel guage should move up and down too. The gauge reacts a little slowly, so don't move it up and down quickly.
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