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MG MGB Technical - Intermittent fuel guage

The guage on my 72 GT reads ok when the ignition is switxhed on but then dies. Any ideas, please?
R W Symonds

Hi.

My first guess would be the instrument voltage regulator.

Is the temp gauge working normally ?, if it is, the regulator is OK, suggesting a poor connection somewhere between the gauge and sender or maybe the sender itself.

Don
Don

Did the 72 B have an electronic oil gauge?
Is you car an ex-American car, RW S?
Cecil Kimber

Bugger not enough Port...got my wires crossed!
Cecil Kimber

UK cars never had the electric oil gauge, and the electric temp gauge only when they split in late 76. If it only happens when you start running the car then it could be a break anywhere from the green (fused ignition) feed to the stabiliser, through that and the gauge to the tank, and through the sender to ground. But if the gauge moves up and then back down by only turning on the ignition and not starting or running it then the stabiliser would be my first guess too. Locate the stabiliser which should be screwed to the lower edge of the firewall behind the dash on the drivers side. Turning on the ignition you should have a constant 12v on the green wire, a constant 12v on the light-green/green for a couple of seconds or so, then it should start pulsing 12v on and off about once per second. If you have 12v on the green OK but not pulsing on the other wire then the stabiliser is faulty.
Paul Hunt

Thanks for the input so far. When I said intermittent, I didn't really make myself very clear. The guage sometimes comes on with the ignition but then dies shortly afterwards, but sometimes, like today, it never budges. As far as I can make out from the wiring diagram, the voltage stabiliser feeds only the fuel guage on this UK 72 car, so it seems that Paul's checks will need to be carried out (when I can find some light!), though I'll check the earth from the tank sender unit first.
Rob Symonds

check this diagram
http://www.mgcars.org.uk/electrical/fuel1.html

will help...
alfredo

If the volt reg. is ok, then check the resistence across the 2 terminals,(disconnect them first)if resistence present then set your voltmeter in amp position, and connect the probes in series with outgoing conection of the fuel gauge,
start the engine, you should have a reading, if it drops after while then you know thats the internal resistence of the gauge.

Alfredo
alfredo

This thread was discussed between 02/01/2005 and 03/01/2005

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