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 Midget and Sprite Technical - Fuel Guage reading

Onto the next job on my list now.

The fuel guage of my 1979 1500 midget appears to work fine, rising to the full mark when I fill it up and decending slowly (ish) as I burn fuel. However when the guage gets below half way it seem to stick, or decend very slowly. So much so that I ran out of fuel when the guage still read just under half full.

Is this a quirk of the Midget? and will a new fuel sender unit in the tank sort the problem? Whilst I'm happy to refill each time the guage reached half full, I'd prefer it to read more accurately.
Eamonn Spencer

Eamonn,
rather sounds like faulty gauge but it's might be worth checking all wires and connections are clean, secure and protected from the gauge to voltage stabiliser back to tank

I'm not sure if the voltage stabiliser has to in a certain orientation of fitting to work properly or not

some owners have been able to recalibrate their gauges, I don’t know if this would be the case with yours but if you look up gauges in the Archive you should find the details
Nigel Atkins

Gauges tend to be reasonably reliable and fairly accurate. Normally, they either work or they don't.

I would hazard a guess that there is a problem with the sender.
Dave O'Neill2

yes certainly check the sender

my previous fuel gauge used to be reliably empty at 1/4, I did think about trying to reset it but just got used to accepting that 1/2 actually meant a 1/4 then it stopped working altogether ang got replaved and as Dave say is fairly accurate
Nigel Atkins

Thanks guys. I think I'll start with the guage. One of the previous owners has done some diy re-wiring around the dash and must have had a job lot of red wire. It's proving difficult to fathom his logic, so it stands to reason that the fuel guage may have recieved his attention also.

I have recieved advice on here before about testing the temperature guage by connecting the live direct to the battery which caused the needle to rise slowly to maximum. Would that work with the fuel guage as well? At least I'd know then if the guage itself was functioning properly.
Eamonn Spencer

Eamonn

If you're ok with a multimeter the below link may be of interest. I've just fitted a new sender to my B and I was able to check the accuracy of both the sender and gauge. The new sender was giving accurate readings (as you'd expect) but the gauge wasn't correct at the bottom end. I'd always had a feeling it wasn't going down to the bottom when empty and this proved it. Fortunately I had a spare 1500 Midget gauge which was accurate so I fitted that. If I hadn't had the spare gauge I'd have recalibrated the original, which I will do when I get the time so I've got a spare.

http://chicagolandmgclub.com/techtips/mgb/f-gauge_cal.html

Bob
R.A Davis

Could be worth checking the voltage stabilizer I think it should give a constant 10v dc I have had faulty ones which affect gauge readings.Article about them here
http://www.chicagolandmgclub.com/techtips/midget/stabilizer.html
mark (1977 1500 Midget) Preston Lancs

The voltage stabilizer doesn't give a constant voltage but switches on and off, being on about 80% of the time and off for the other 20%. You can however get a modern electronic version that maintains the voltage at 10V without switching on and off.

If the problem were the stabilizer, a high reading on the fuel gauge would indicate the unit is not cycling as it should and is on full time, this would be easy to check simply be measuring the voltage at the stabilizer. However this would also affect the temperature gauge that would be reading high, this may not be as noticeable as the effect on the fuel gauge.

My money is on the sender, I suspect the float arm is not being allowed to drop all the way down. A simple test is run the tank almost empty and use the figures in the link to check the reading. The figure for 1/4 tank is 105 ohms and 220 ohms for empty, if you get less than this it's the sender otherwise it's the gauge.

Bob
R.A Davis

I forgot about the water temp gauge being electric too

if it should turn out to be voltage stabiliser here are two modern alternatives

http://www.ebay.co.uk/itm/SOLID-STATE-VOLTAGE-STABILIZER-MG-Midget-MGB-MGA-/130679018413?pt=UK_CarsParts_Vehicles_CarParts_SM&hash=item1e6d1393ad

the one I have is this but I don't know if it's still going as it's not on eBay anymore -
http://classicstabilizers.webs.com/contactus.htm

but check as sender and gauge and connections first
Nigel Atkins

It depends on how old the car is some 1500 temp gauges or mercury one with a bulb in the thermostat housing and the voltage stabilizer only works the fuel gauge
mark (1977 1500 Midget) Preston Lancs

Not got round to looking any further at this problem yet due to the weather but could a voltage stabiliser problem also account for the rev counter being slow to kick in and when it does, flicking straight over to red line before settling down to apparently reading accurately?
Eamonn Spencer

The tacho shouldn't be connected to the stabiliser. Just the fuel gauge and, as Mark says, the temp gauge in late 1500s.
Dave O'Neill2

This thread was discussed between 12/04/2012 and 17/04/2012

MG Midget and Sprite Technical index

This thread is from the archive. The Live MG Midget and Sprite Technical BBS is active now.