MG-Cars.net

Welcome to our resource for MG Car Information.

Recommendations

Parts

MG parts spares and accessories are available for MG T Series (TA, MG TB, MG TC, MG TD, MG TF), Magnette, MGA, Twin cam, MGB, MGBGT, MGC, MGC GT, MG Midget, Sprite and other MG models from British car spares company LBCarCo.

MG MGB Technical - faulty fuel gauge

Ran out of "petrol" today even though my gauge said I had 1/4 tank. How can I fix this?
Tony

Have you replaced the sender recently? Those currently available are significantly different to the originals, requiring gauge recalibration at both ends. See how on http://www.mgb-stuff.org.uk and click on 'Spanners', 'Electrics', 'Gauges' and scroll to the bottom.
Paul Hunt

Does anyone have an accurate fuel gauge in an MG? I always rely on the trip meter to decide when I need to fill up, even in my MGF (which I've just sold) and my MG ZS (which I've just bought). Too many bad experiences of running out late at night in the pouring rain miles from nowhere when the gauge insists that there is still at least a quarter of a tank of fuel left have taught me this technique.

Ralph
Ralph

You can also add a ground wire from the tank to the body , this has helped me in other LBC's .

I recently repaired some DPO wiring that had been causing low battery charge and dim lights etc. , now the previously _perfect_ fuel gauge is like all the rest and is empty when reading 1/4 tank - best to just fill up when you reach 1/2 indicated .

-Nate
Nate

My fuel guage was accurate until I replaced the sender. I've had to calibrate the fuel guage to its absolute outer limits. Otherwise at empty it would register 1/4 tank and when full would read 3/4 tank.

Having done this though, the guage is now much more 'sensitive' to hills, the needle often vibrates when at 1/4 tank or below, and when full, the needle still often registers low. All of this detracts from accuracy.

My old sender's arm had a zig zag bent into it, causing the float to be closer to the pivot. I've wondered if I bent the arm in the new one likewise, could I de-sensitize my guage a bit and come back to the reliability I had before? Or is it a matter of different windings in the electrical portion of the sender? Anyone checked this out?
Matt Kulka

I always just keep 5 gallons of gas next to the spare engine in the trunk.
J Arthurs

Hmm. I used to drive a 1960 Volkswagen with a "reserve tank." That was cool. Of course, it was built without a gas gauge. Made it kind of neccessary.
Matt Kulka

It's as accurate as you make it. Replacement senders are *not* the same as the originals which is why recalibration is necessary when replacing the original or an OE. The originals were good enough at E and F and can be made the same with recalibration. Linearity is another issue, with both old and new types.
Paul Hunt

This thread makes me feel lucky. When my fuel gauge failed to read properly, I followed the advice on MGB Electrics referenced in the Paul Hunt's post and quickly determined that the sender unit was at fault. That is an excellent guide.

So i got a new sender unit, a breeze to install and the gauge reads just as "accurately" as the previous one. At about 1/8 full, the gauge’s needle starts to flutter (a lovely design feature) and then the tank takes about 46 liter of fuel.

BTW - I also use the trip meter as my check (do that on any car I use).

Cheers
Peter
67 MkI MGB
Peter Vann

The fuel guage in my '63B reads full all the time, but it doesn't just shot up there, it takes a few minutes. I have replaced the sending unit but that didn't do anything. And I even ran a jumper from the sending unit to the guage, bypassing the factory harness wiring, but still no change. First off, where is the voltage stabilzer? Do I even have one? The Moss catalog doesn't even have a listing for one until 1965. HELP!!
Todd

On my 67 the voltage stabilzer is located on the inside of the bulhead above the steering column. The fuel gauge was the only gauge that used a voltage stabilzer on the MK1 cars. The lead from the voltage stabilzer to the fuel gauge should read about 10 volts. If it reads a full 12 volts or higher with the engine running, then you will need a new voltage stabilzer. Cann't help you on the gauge reading full all the time, mine does the same thing.

Jim
Jim Lema

My gauge was reading high also. What I did was buy a set of resistors of various amperage from Radio Shack and soldered spade connectors to each side. I then put them in line where the wire goes into the sending unit. I also wrapped them in heat shrink althouth this was for looks only. The resistors will lower the voltage coming out of the sending unit. You will have to play with several amp resistors to get the one that is right for your particular car.
Drew

I checked my factory shop manual's wiring diagrams and '62 to '64 B's do NOT have a voltage stabilzer. I think I will try Drew's advice and try to knock down the voltage going to the gauge. In 15 years of ownership, I've only ran out of gas twice, but I would still like to fix this!
Todd

Early Bs had a coil type fuel guage which does not need a voltage stabiliser and changing the voltage should have no effect whatsoever unless a later bimetallic spring type guage has been fitted.
Chris Betson

Chris,

Any ideas how I can fix my gauge to read correctly since it is a coil type? Does my gauge need to be rebuilt or recalibrated? Thanks
Todd

Re Matt Kulka's contribution. I owned a '53 beetle that had the perfect answer, ie. no petrol guage, just a wooden dipstick. Worked a treat, except when checking it in snowstorms or pouring rain at roadside.:-)
Danny

For calibration of the early gauge - *if* it is the same as the one used in the MGA - have a look at this site. Another page that describes how the gauge works shows the meter showing F when the wire from the sender is *disconnected*. This is opposite to how the later gauge works. This type of gauge has three terminals whereas the later type only has two, so check that first. You should be able to get the gauge to read E by grounding the T (for Tank) terminal.
Paul Hunt

Yes Paul, I think it is the same one used in the MGA and early Sprite/midget.
Chris Betson

This thread was discussed between 24/10/2002 and 31/10/2002

MG MGB Technical index

This thread is from the archive. The Live MG MGB Technical BBS is active now.