FUEL SENDER UNIT FAULTY ?

[mattyb]

the fuel gauge on my 1966 (black face speedo) only registers empty - if I earth the connection from the fuel tank sender unit, the fuel gauge moves up to full - does this mean the sender unit is faulty ? what can I check on the sender unit ? ( mindful of the dangers involved !!)

many thanks

MATT

[GeordieDave]

Sounds like it

If you have a multi meter, remove the sender from the car - remembering that petrol vapour is flammable - set the meter to a resistance setting then connect one probe to the sender housing and the other to the electrical connector. As you move the float, the resistance reading on the meter should change. If it doesn't, your sender is faulty.

You can also check the function by using the 20V setting on a multimeter without removing the sender, connecting one probe to a positive or negative feed (which ever way your car is earthed) and the other probe to the sender's electrical connector. Rock the car - the voltage should change because the sender is basically a big variable resistor.

[mattyb]

Cheers Dave

I'll remove the sender unit and test it like you suggest -(presumably if I remove the sender unit and the float has a hole in it I'll know why its reading empty !!)

many thanks

Matt

[GeordieDave]

Cheers Dave

I'll remove the sender unit and test it like you suggest -(presumably if I remove the sender unit and the float has a hole in it I'll know why its reading empty !!)

many thanks

Matt

I hadn't thought about the float having a hole in it - I always over think things, so I'm told

I don't know if the sender can register 0 volts when the tank is empty or if there's always a small output to make the gauge needle move up to the E position. Does your gauge move up to E when you turn the ignition on? If so, I'd say you have a hole in your float!

[mattyb]

Cheers Dave - yes gauge does move up to "empty" - I'm going to have a look at it today so will report back !

nothing wrong with thinking ! though Shakespeare wrote "he thinks too much, such men are dangerous"......... !!!

cheers again