MG Midget Forum

So I took my midget on its maiden voyage and had worked out grounding problems with my fuel sender. It was showing a steady 1/2 tank so I was pretty pleased. Anyway, during the first mile, the car sputtered and died. No gas in my fuel filter and I had to tow home. Thinking it was a bad fuel pump, I switched it out for a brand new one and there was still no fuel. It then dawned on me that I was truly out of gas (rookie mistake) and after putting 7 gallons in it, it fired right up. The fuel gauge went up maybe an 1/8 of a tank showing about 2/3 full for a full tank. So, the gauge range seems to be 1/8

My question is, is this a fuel sender issue or did I accidentally mess with gauge adjustment while I had it out of the dash? Is there a zero and full adjustment screw on it?

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1972 MG Midget MKIII "The VB Weller"
55,400 Miles
Watkins Glen, NY

Unless you somehow messed with the gauge internals, I would suspect the sender, assuming the wiring is all good.
Unfortunately the fuel tank has to come out to get to the sender.

I think you could try to measure the resistance of the fuel sender when the tank is full and empty with the tank in the car.
Disconnect the wire to the sender, then measure resistance of the sender with a full tank, 1/2 full tank, and an empty tank.

IIRC the tank full resistance is around 20 ohms and around 250-260 ohms at empty (I could have the numbers off, someone will
correct me I'm sure).

Thanks for the advice. I have a new sender sitting in a box which I could hook up. Not sure why I didn't think of that before. At least that would rule a host of things out like the gauge and regulator.

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1972 MG Midget MKIII "The VB Weller"
55,400 Miles
Watkins Glen, NY

If you do not want to drop the tank for a while, use the trip meter as a refuelling guide. I have the same problem.

I reset the trip meter when refuelling - 6 Imp Gal @ 38mpg - gives me a 180 mile refuelling point, plus approx 20% reserve.

Good idea. I use the same method on my BMW motorcycle only that at least has a low fuel warning light.

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1972 MG Midget MKIII "The VB Weller"
55,400 Miles
Watkins Glen, NY

My first MG was a MG TC. No fuel gauge, just a warning light when you had about 50 miles left. Loved that system and I never ran out of gas. When the light started flashing the next mission was finding a gas station.

Kurt

Oh, the other thing I forgot to mention is to ensure nothing is interfering with the movement of the gauge needle, in either direction. Sometimes some debris like a failed gauge face seal can find its way into the path of the needle. But I think it’s more likely your sending unit is bad.

Scott,

If the car hasn't been driven in many months or years, the float for the sending unit may just be stuck in a given position.
If so, driving the car for a while may get it unstuck and return it to working properly. The gas sloshing around in the tank may work it loose.
It happened to a friend's early Miata.
Worth a try before dropping the tank only to find out it wasn't necessary to do so.

Pete

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In 1974 when I was 18, I passed on buying a running and driving 1966 Jaguar E-Type coupe for $1,500, which is what they were selling for at the time.
Fifty years later, I'm still kicking myself...



Edited 2 time(s). Last edit at 2024-04-22 01:26 PM by pbcjr.

i allways carry a gallon of fuel in boot,never run out and been stuck in the middle of the devon country side

The 74 midget came with some PO paperwork including a home made log book with "150 mile range" written on the cover. Getting gas at 150 miles and resetting the trip odometer is a SOP.

The 59 Beetle has a log book with milage, gallons added that dates back to Feb 59.

If your 'new' sender's resistance range isn't on par or close to the OEM range of 20 to 220 ohm, your gauge readings will continue to be in error.

I made the mistake of ordering an "Improved" sender from one of our usual British car parts suppliers, and it was WAY off on ohm range.
And non-adjustable for calibration.

The "Improved" component of this sender was only a 'solid' float.
This unit is the 'white plastic' edition.

Since there was no way to 'subtract' resistance from the new sender, I increased the circuit voltage to 12V by eliminating the 10V stabilizer.
This was after calculating the amperage rise across the total circuit resistance (gauge, sender, and wiring) and finding it to be so little that I felt secure no 'over current' would be imposed on the gauge heater winding.
Now changing fuel load is reflected quite nicely by the gauge indications.

Don't have the calculated values at hand, but will post here if anyone interested.
No problems after approximately 20 hours road and shop running time.

Wow, a lot of great advice here. I don't believe the gauge is stuck because I'm still having signal issues where the fuel gauge falls to zero and then returns to the 1/2 - 2/3 position. Never more, never less. When I had the gauge out for service, I tested it using the grounding trick too. It worked full range.

I'll check the resistance of the new one against the gauge too. Interesting comment on the voltage regulator.

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1972 MG Midget MKIII "The VB Weller"
55,400 Miles
Watkins Glen, NY

There is also an early sending unit and a late sending unit used with the gauge that uses the voltage stabilizer which your year has.

Dropping the tank is NBD. Easy to drain if you have a plug, easy to siphon if you don’t.
Good chance to clean it.

I use my fuel pump and run it out the front to drain.

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79' Midget with a Weber Carb and more beer than gas.

My tank does have the plug which I was happy to see. Looks like you remove the filler pipe, disconnect the charcoal can vent line and maybe one other to the overflow flying saucer thing on the passenger side trunk reinforcement, disconnect the fuel pump feed and the fuel sender wiring. Six bolts and down she comes?

Good to note on the fuel sender type. I'll have to look at the new one that came with the car to make sure it's the right one before making the effort.

Thanks for your help.

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1972 MG Midget MKIII "The VB Weller"
55,400 Miles
Watkins Glen, NY