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MG MGB Technical - Fuel tank level indicator float

I just bought a 74 1/2 "B" and the owner said "don't trust the fuel gauge". I had a midget that I was able to clean the in-tank fuel level indicator rheostat so I took this one out to look it over. It measures between approximately 17 Ohms for FULL and 277 Ohms for EMPTY. (I think I have the order right but it isn't real important. Point is it seems to work). What I noticed though was that there was a small amount of liquid in the float, presumable gas. I would say about 1/8 full or less. My question is whether this is normal and, if not, is there anyplace to just order a new float instead of the whole sensor? Also, if someone can confirm these Ohmmeter measurements I would appreciate.
Tom

No, alas the float shouldn't have any petrol on it.
I adjust mine by the process of bending the little wire arm so that it read empty (on the guage) when the float was resting on the bottom of the tank, and half full when half way.
Peter

Tom -

You can purchase the float itself from the Bhive:

http://www.thebhive.com/105MGB70-76gastank.htm

$12+change (although a new sender including the float is about $25). By coincidence I had to do this last week on my 74.5.

Greg
Greg Smela

I have had good luck by using a small soldering iron on the float itself. Find the leak by heating the float in very hot water,drain it out. you may have to use a very small drill to enlarge the hole. Then with the hot iron just remelt the float and it can be resealed. Doing that at a cost of just time may save a few bucks. If it don't work then replace it. You do not have to drain the tank. Just jack the car up on the right side and with a half tank of gas or less you can remove the sender. Takes 10 minutes.
Sandy
Sandy Sanders

Those resistances are about right, and there shouldn't be fuel in the float as others have said. I had a similar problem with a carb float, couldn't find the leak so drilled a hole to drain it, resealed it, but that leaked as well, so personally I wouldn't bother with that again, just replace the float straightaway.

Senders seem to vary quite a bit which can put the gauge way out after a replacement. Rather than fiddling with the float which may take several in and outs to get right the gauges are adjustable. On the back there should be two holes in the case, which may be covered by cork plugs. In the holes are slotted plates. Twist these to calibrate the gauge - the one by the F for the full setting and vice-versa. However use an implement that fits the slots as well as possible, they can be very stiff and a too-small screwdriver can 'round them out'. Do the F calibration first, then run the tank right down to do the E. I put a gallon back in and *then* adjusted for E, to give me something of a 'reserve'.
Paul Hunt 2

This thread was discussed between 22/04/2007 and 23/04/2007

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