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MG MGB Technical - Early B Fuel Gauge Problem

My 64 B fuel gauge jumps quite a bit while the car is moving. I installed a NOS sending unit and had the gauge re-built. I looked through the archives and have read that this was a common problem. Comments suggested that fitting a voltage stabilizer would not help but a large capacitor (what size) fitted in series might do the trick. Has anybody been able to find the correct fix?

Thanks

Les
Les Jacobs

Les - I don't know what size the capacitor whould have to be, but you don't want it in series. It would need to be either across the gauge terminals or wfom the terminal that gets the wire from the sender to ground. One sould have to experiment a bit with it, unless there is someone out there who has already done the work. Cheers - Dave
David DuBois

Thanks Dave

There must be someone out there that has solved the problem. I did read in the archives that one chap used a voltage stabilizer wired I believe as you described and got some good results

Les
Les Jacobs

does anyone have maybe a thought?
Les Jacobs

The early gauge was very sensitive to instantaneous movement, which was why the later thermal system was developed. However since motorways were also developed with their long curves exactly the same thing happens, but takes longer to show the correct fuel level when you straighten up again. Baffled tanks were also a factor in trying to prevent the gauge sender flapping all over the place. A voltage stabiliser will do nothing, other than even out variations in the supply voltage from the dynamo (which was another feature of the later thermal system), it won't have any effect on gauge variation from cornering forces. As David says the capacitor would have to be across the gauge or the sender, if in series you would only get any gauge indication when the sender was flapping about, which is the opposite of what you want. Due to the low impedance of gauge and sender (in the low hundreds of ohms) you would have to get quite a large capacitor to give you a significant time-constant. But at the end of the day does it really matter? Unlike an oil gauge or temp gauge where you would want an instantaneously accurate reading, a fuel gauge is going down at a relatively constant rate, and only slowly at that. The MGB gets an unfairly bad rap for its fuel gauge, my 1989 Toyota Celica is far worse.
Paul Hunt 2

Paul

Thanks for your comments.Seeing the needle bounce back and forth as I drive is at worst an annoyance. Just thought there may be an easy fix out there.

Les

Les Jacobs

This thread was discussed between 11/04/2007 and 13/04/2007

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