fuel gauges

[stevey]

I suppose this gets covered all the time, but both my car and my brothers minor have developed fuel gauge faults. Mine with the ignition on slowly reads correct, but as soon as the engine is started the fuel gauge swings to full. On my brothers it is the opposite it reads right with the ignition on then goes to empty after a while doesnt matter whether the engine is started or not.

ive change the regulator and gauge in my brothers but nothing works, is this likely to be a faulty sender unit or bad earth? Mine worked till two days ago, any ideas?

Well im away for a week of sunny bliss so theyll both still be there annoying me when I get home.

Thanks

[Rob_Jennings]

On your car it sounds like the regulator for the gauge.

I would guess that it has failed 'on' so that without the engine running you have 11-12 volts giving a reasonable fuel reading, but when you start the engine it rises to 14-15 volts giving a high reading (full most of the time). If you have a multi meter you could check the voltage on the instrument regulator output to confirm that.

On your brothers car I don't know, but would suspect the sender is at fault.

[Kevin]

Have you checked that the tank sender connection is OK and while you have it disconnected use another piece of wire to extend it to a convienient earth point then turn the ignition on if the guage is OK it will go to full and you know there is a sender fault if not the fault is elsewhere, but this test eliminates one side or the other quite quickly and its often the tank connection with some corrosion on it.

[stevey]

Cheers people mine was the regulator unit. I tried the earth on my brothers motor looks like its at fault. Thanks for the assist.