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MG MGA - A calibrated manual fuel guage?

A few MGA owners I know carry a manual fuel guage (a stick - 60 centimeters long) as they haven't got around to fixing the Jaeger unit. Has anyone taken the trouble to calibrate their stick?
Mike Ellsmore

This is what I used in my Cessna; it would still have to be calibrated for your tank, but it looks like a scientific instrument and you wouldn't have to feel ashamed when you checked your fuel level with a stick.

k v morton

This must require very careful balance and a sure step to use in flight, Ken.
Ken Korey

It's not much worse than reaching the gas cap from the cockpit of an MGA while on the road, but it is one reason I gave up flying....

k v morton

My fuel gauge works (in a fashion) but the needle shows half -full when in fact the tank is empty. (Which indicates that I am optomistic in nature as opposed to my wife who would say it shows half empty!)

So I too have thought of making a fuel "dipstick" to help solve the problem.

So far I have not collected enough 1 gallon containers of fuel to be able to fill a completely drained tank one at a time to allow me to calibrate a gauge like that. (thats a lot of petrol to leave lying around in the garage!)
If you could get to a gas station you could I suppose in theory you could carry this out next to the fuel pump.
However, I think the gas station may not take kindly to you draining the tank on the forecourt and to filling one gallon at a time creating a roadblock at the pump.

So I think I will drain the tank at home, pour in two measured gallons of fuel, one at a time and mark the dipstick at each level. Then drive to the gas station and fill the tank to top (level with the bottom of the filler hose) and mark this as the full level on the dipstick.

In theory, I should be able to use the measurement between the 1 gallon mark and the 2 gallon mark to calibrate the rest of the dipstick.

I will let you know if it works. It will be great to be able to leave the spare gallon of fuel I normally carry in the boot at home.

Unless anyone can sell me an accurate sender unit first!


( may have to calibrate in litres over here )
Colyn Firth


The optimist says the glass is half full, the pessimist says the glass is half empty. The engineer says the glass is twice as big as it needs to be!

Seriously though, why not spend your time fixing the sender/gauge?
Neil McGurk


these manual gauges work a treat! I have a calibrated 24 litre version fitted as standard to my Trabant (I also have an optional aftermarket electrical gauge). It slides in udner the bonnet support, just above the fuel tank which is just above the engine.

Coupled with a "reserve" setting on the manual fuel tap (yes, it uses the most powerful pump in the world - gravity), means that you only need to worry about accurate fuel levels when filling up. It needs to be accurate so that you can work out the amount of 2-stroke oil needed to mix in when filling up, to avoid doing a James Bond and creating a huge cloud of smoke when you pull away.

Have fun,

Grant :-)
G Hudson

My gauge works okay down to half, then falls rather quicker for the final half. However, it reads accurately at empty as I know to my embarrassment.

I usually reset the trip at each fill-up to full. When I have done 200 miles on local type of trips I know it's time to start looking for the petrol station.

We used the same sort of logic when flying the fast jets. We knew how many lbs/kgs of fuel we used for every 100 miles both low level and high level. That type of logic kept me basically safe over the years.

Steve Gyles

I wonder how long it will be before we see one on ebay, counting me there is already two dipsticks in my car another would only serve to confuse,
Vin Rafter

Just had a thought with my Heath Robinson hat on.

Using 4 weight sensors that you find fitted to the base of modern electronic bathroom scales, you could fit them to the inside of the tank straps as the contact points for the tank to sit on. Knowing the weight of the empty fuel tank when all secured up, you could then zero the readout, fill up with fuel and run a constant read out of fuel weight- converted to gallons with the appropriate factor!

A few engineering issues to overcome, but possible?

Now, will the wife miss the scales? She says she is overweight and won't stand on them!

Steve Gyles

I've got the (non-original) Mini-van sender fitted to my MGA. The reading when full is off the scale (F) but does show the level as it is less than approx half full. The reading when empty is at the end-stop (E).
Dan Smithers

If you do so, you might need an averaging algorithm, as cornering and such will cause drift of the sensors, I believe. You might also want a longer average so that bumps would be minimized.
Mike Parker


You are undoubtedly right. Probably easier to scavenge a set of sensors out of a scrap fighter jet. I have often wondered how the fuel weight sensors worked on the aircraft. The gauges never seemed to flinch, be it upside down or pulling 6G. We never got into that level of detail on aircraft systems in ground school.

Steve Gyles

The other option is to use Queenslanders' logic when reading the gauge (gage). E=Enough and F=Finish! They cannot work out why their cars keep stopping.
Mike Ellsmore

My gauge was "all over the place" when I first got my car. I calibrated the gauge it using the instructions on Barney's site, and it is now very accurate. There are two screws on the back of the gauge which you slacken and slide. You will need two 68 ohm resistors.
Lindsay Sampford

Hi Steve,

If you are interested, as with most aircraft, the Frightning fuel gauge used capacitance to measure the fuel quantity. Basically a rod for the anode and a concentric tube as the cathode, the Avtur was the dielectric, several were used around each tank. An absolute sod to set up but very accurate as it doesn't matter where the fuel is along the tube it will always read the same capacitance.
Another little capacitor allowed the density of the fuel to be corrected to give pounds instead of gallons.

If I remember correctly, the test set was called the TF20 and looked like Pontius probably used it.

If course this type of gauge would work very well in an MGA if you can find a suitable display, I could probably find an old Hercules sender if anyone has a burning urge to try.


P Reardon

Thanks Paddy. You speak with the authority of someone from Boscombe Down?

Steve Gyles

Lindsay, do you think my fuel gauge can be calibrated enough to compensate for it showing half-full when the tank is actually empty?
It does read full when the tank is full.
Colyn Firth

Hi Steve,

Not at all, Spent half my career inside Hercules fuel tanks (at a secret airbase in Wiltshire), you can't fail to notice the electricians bits when they get in the way all the time.

Gave me a taste for 1950's technology though.

Back slightly on subject again, why not do a bit of measuring of the tank and work out the depth for each gallon. You don't need to get too excited about the curves etc. just a rough area of the bottom.
1 Imperial gallon = 0.161 cubic feet or
1 US gallon = 0.134 cubic feet

The first gallon would be a bit inaccurate but the rest should be OK.


P Reardon

Colyn, just follow the instructions on Barney's site. It's a bit of a fiddle, because the two adjustments affect one another, but with a bit of patience, and assuming your sender unit and wiring are OK, you should end up with an accurate gauge. The adjustment of the gauge itself is not dependant on the sender unit, so if it doesn't display correctly after calibration, it means your sender is faulty.
Lindsay Sampford


Is there any advantage with the mini-van sender unit over other MGA replacement types?

It would appear from your post to work quite well.
John Bray

If anyone is in need of a fuel gauge I have a Jaeger faced 5303-05 one to sell in its original Smiths box. I tested it yesterday when doing some work under the dashboard and it works just fine. Don't think it is NOS as it seems to have had the casing resprayed at some point, but it is certainly in great condition. I'll let it go for $100.

I'm quite surprised at what is emerging in my cellar at the moment.

dominic clancy

This thread was discussed between 02/11/2010 and 07/11/2010

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