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MG MGB Technical - Early B fuel gauge

I have the last job to figure out on the B that I have rewired. The fuel tank has fuel, but the gauge shows emoty.

I have checked the Green/Black wire to the tank sender, it shows continuity for the whole length.

I have taken the Green/Black wire off the back of the gauge, and it then instantly reads full.

The gauge worked before the rewire, so did the sender, which has not been disturbed apart from tightening the screw holding the tab for the earth cable. Earth also shows no resistance.


Where should I look next ?
dominic clancy

Dominic. If memory serves me, the fuel gauge needs to hook through the gauge voltage stabilizer.
Bruce Cunha

Dominic-
Pretty certain this early B is the same as MGA, so check Barney. No voltage stabiliser on these.
IGN W > fuse > G > gauge > GB > tank unit > B earth.
See: http://www.mgaguru.com/mgtech/electric/fg_01.htm
and many more pages! A true opus magnificus.
(that's for the MGA one; go back to imdex for the later MGB one of you need to)

FRM
FR Millmore

Fletcher is correct, the early MGB gauge is the same as the MGA gauge. These are not the taught wire gauge used in the later MGBs and do not us a voltage stabilizer. The mgaguru site is a good source for information on the gauge. Cheers - Dave
David DuBois

Do you have the right sender for the gauge? The early system works completely differently to the one that uses the stabiliser. The early uses a Wheatsone Bridge which is supply voltage independant, the later uses a variable resistance and so is dependant on supply voltage hence the stabiliser.
PaulH Solihull

Earth - "which has not been disturbed apart from tightening the screw holding the tab for the earth cable. Earth also shows no resistance."

On the basis of checking the last thing disturbed.....Really 0 ohms? Recently I had a similar thing. I thought good earth-it turned out to be 10 ohms. Not much, but if my maths is right that means the current is reduced by a factor of 10!
Michael Beswick

This thread was discussed between 15/12/2011 and 16/12/2011

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