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MG MGB Technical - Fuel Gauge not working

From looking through the archives and also the link to the pages of "Bee and Vee" it appears that fuel gauge problems are fairly common. The gauge in my 1974 MGB GT worked fine until I took the car off the road to rebuild it. Unfortunately the rebuild took 3 years (off and on) and now that the car is back on the road I have everything working well with the exception of the fuel gauge.

Since putting the car back on the road the gauge has not worked at all but other things demanded my attention such as a leaking fuel tank, replaced with a new one, a fuel pump that refused to work, replaced with a new one etc. I also replaced the tank sending unit along with the tank but this doesn't appear to have helped. I have pulled the gauge and confirmed that I have power to the green wires at the gauge, I checked continuity of the green/black wire to the fire wall and then to the tank sending unit and back to the gauge and finally ran a ground from the sending unit to the car body even though there wasn't one previously. None of these things has resulted in a working gauge.

What are the chances that the new sending unit is faulty? How would I check this unit?

Brian


Brian Smith

Have you tried giving the gauge a bit of power from a known good source to see if the gauge is good or not?
Ross Kelly

First thing I'd check is the gauge and its associated wiring. To do this disconnect the gauge wire from the tank unit and earth it at which point the gauge should read Full. This being the case the fault lies in the tank unit.
Iain MacKintosh

Dissconnect the wire from the sending unit and touch it to the chasis, if the gauge makes a full swing the problem is the sending unit.

Pictures of the presently available replacement sending units have shown them to be junk. Put your old sending unit back in if you still have it.

John H

Nice looking car Brian.
Mike Howlett

Thanks all. By grounding the wire at the tank and turning on the ignition the gauge moved towards full so that would seem to confirm that my new sending unit is no good. I appreciate the help.

Mike, thanks for the comment, the GT was used every day for many years as my main means of transportation but I never did get used to the "Harvest Gold" and rostyle wheels so decided when I retired to rebuild it. I had a BGT when I was young that was red, had wire wheels and OD so decided that I really wanted to make the changes to this car. Some of my pictures are on the web site at http://www.island.net/~btsmith/index2.html .

Brian Smith
Brian Smith

Just a quick update. The replacement gauge arrived and has been installed and works great. I first hooked it up outside the tank and checked that it worked before removing the old one. All that is required now is to ensure that the gauge calibration is correct. Nice to have everything working again!

Thanks all for your advise and guidance.

Brian
Brian Smith

This thread was discussed between 29/04/2008 and 04/05/2008

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