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MG Midget and Sprite Technical - Fuel tank sender & Gauge

I'm trying to establish the resistance in ohms that the late (last) fuel tank sender produces to get a reading on the guage.

I'm advised that

30 Ohms = Empty
120 Ohms = Full

Does this sound about right?

Daniel Thirteen-Twelve

I have just refitted my fuel tank tonight, but before i did, i put a meter across the sender unit, the result was 230 ohms for empty and 25 ohms for full, (i turned the tank upside down for this test, which I thinks should simulate a full tank)
By the way, the car is a 78 1500 and the fuel gauge was working ok last time i used the car, which was XX years ago.

HTH
Alan
Alan

Thanks even though I'm now confused! Iv'e send my apare sender away to the gauge supplier so get a definite(ish) response.
Daniel Thirteen-Twelve

You have the right to be confused.

With at non-functional gauge myself I have just just briefly investigated this as the fuel gauge is not on the top of my list of projects. However I know that there are at least two sender and two gauge types used in spridgets making this a confusing topic.
This guy http://pjprofili.com/cars/sprite.html#fuel has had the same experice.

The figures from his investigation (for the archives) are:

Original Type Sender
Full 100 Ohms
Half 60 Ohms
Empty 10 Ohms

Later Type Sender
Full 14 Ohms
Half 90 Ohms
Empty 258 Ohms

Original here refers to his '66 Sprite. This matches what Alan got for his '78 1500 midget and that would be a "Later Type" (surprise!).

Now the million euro question is when the change happened. I leave that up to someone else to answer.

When talking about non-functional fuel gauges it might be intresting to mention the voltage stabilizer that needs to be ok in order for the gauge to work.
This article explains a bit about it:
http://www.chicagolandmgclub.com/techtips/midget/stabilizer.html
and there is a very nice article about this issue at:
http://home.mindspring.com/~purlawson/files/SmithsVoltageStabilizer.pdf

//Erik

E Lindgren

Early gauges like the one on my MK I Midget (948, with flat dashboard) were moving coil types: when you turn on the ignition, the needle immediately moves to register the tank contents. In fact the needle constantly moves around as the car is driven.

Later gauges use a hot-wire to heat a bi-metal strip that bends with temp to deflect a needle; this movement is damped, and the needle takes 5-10 secs to register when ign is turned on.

You can imagine that the sender for each type is different.

A
Anthony

This thread was discussed between 15/03/2008 and 27/03/2008

MG Midget and Sprite Technical index

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