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MG Midget and Sprite Technical - Replacement petrol tank sender

It looks as though the tank unit in my Frog has given up the ghost. The gauge passes all the tests listed in the manual and the connection to the sender appears to be open circuit. It may be repairable but if not I shall have to replace it or put a proper handle on the bamboo stick I am currently using (very accurate too!)

From earlier post it appears that replacement for these unit suffer quality issues. Has anyone bought one recently and can recommend a supplier? (note the Frog uses a different unit to the ones in the later cars although I think the one in the Mk 2 Sprite is the same).
Graeme W

I replaced my rusty tank & the sender on my midget 1500 about 18 months ago. It came from Moss. I did um & r about the sender unit. However, I put the new moss one in, touch wood, it's been absolutely fine.
Regards
Nigel Axtell
Nigel Axtell

The one from NOS Locators / Scarborough Faire have the wrong Resistance range and will not work with the early gauges. I luckily bought mine from them over ebay and had to wait for weeks for a refund because there was absolutely no reaction at all to my complaint. Only when the time for them to respond ran out could ebay give me back my money.
dominic clancy

Have you opened it up Graeme? This one is from my '73 Midget, but I don't suppose it was that different to an earlier one, as fitted to a frog. They all work roughly the same way I think.

Worth taking it apart to see where the open connection is. Even if it's the winding, it's liklely that you can fix it.

On this one, it was just corroded and the wiper wasn't making very good contact with the winding. Works a treat now though.




Lawrence Slater

Im dealing with this also, and simple dont want to go thur the hassle it takes to remove the idiot thing

If I have to do this, im seriously thinking of using a 6inch hole saw and drilling out the boot floor, to the sender unit, then just an ally cover patch over the hole with some silicone and self tapers... its not like anyone ever looks at the boot floor. Seems it should be a simple to access the sender after the hole is cut


But it must not be a good idea or others would have done it

Prop
Prop and the Blackhole Midget

Lawrence: there are unfortunately two totally different types. THe early ones have high resistance at "full" and low at empty, and the newer ones are the other way round! The gauges are therefore totally different! However I had already thought I should drop it down before getting a replacement incase it was something simple.

Prop: the problem would be needing to drop the tank in order to drill the hole. You could try the old fishing float idea with a stick and cork on the end which is long enough to poke out of the filler cap and will rise and fall with the gas level. You could even mark it up in gallons! (suggestion: use mirror image lettering so you can read it in the rear view mirror!) If you ventured into far flung places, just have a second one calibrated in litres!




Graeme W

Hi Graeme. I didn't mean that you could use a later one. Simply try and repair your own. Although the resistance is the other way around as you desctibe, it's still done the same way, with a resistance winding, and a wiper. So either the winding is simply dirty, or broken, or the wiper isn't making a decent contact. Even if the winding is open circuit in the middle, it's possible to join it again. You might get a slight 'glitch' when the wiper traverses that point, but it won't make that much difference to the reading on the gauge.

Nobody used to bother to take these apart and repair them when the originals were in plentiful supply, but if as you say the replacements are sub-standard, then it's worth a go. It's only time, and taking them apart is simplicity itself. :).
Lawrence Slater

Prop

The only problem with cutting a hole in your boot floor is stopping before you cut a hole in the top of the tank...or you might make another hole - prop sized - in the roof of your 'shop!
Dave O'Neill 2

Dave..

That is a concern for sure... im hoping ill know when I drill past the boot floor and not over done it into the fuel tank

The idea seems simple enough...im thinking the risk is worth the effort not having to remove my panhard rod, then dropping the tank and im sure bathing my self.in gasoline in the process as the tank falls on my head while dropping it down

With a 6 inch dia hole over the sender thur the boot floor... that would just be to simple, and karma would be pissed off that she got cheated

Is there any reason my idea of drilling a 6 inch dia hole thur the boot floor over the sender wouldnt work ?

Prop
Prop and the Blackhole Midget

one reason it may not work is that you are sure to butcher the cable from the gauge to the tanks sender, as well as the sealing foam around the sender seat. Then you will still not be able to remove the sender out of the hole because the arm will get in the way. And how do you know where to drill the hole to get it exactly centered over the sender? And I guess the hole cutter has a pilot drill in the centre, which is going straight into the sender IF you get the calculation right, and straight through the tank when you get it wrong!

I have the same job to do this winter, it's the only thing on the car that didn't work after the restoration. But the tanke is definitely coming DOWN, rather than even thinking about drilling into the unknown!
dominic clancy

Not sure what all the fuss is about. Taking the tank out isn't at all difficult, and doesn't take that long. But I agree a hole in floor to access the sender would be a good idea. Someone on here put up a pic a while ago didn't they?

So drop the tank. Cut the hole, and make a removable/sealable cover. Put the tank back, and then fit the sender, followed by the cover.

I didn't do it to the Midget, as I wanted to keep that essentially standard for sale purposes. But as I have to drop the tank in my Sprite, I think I'll make an access hole for that.
Lawrence Slater

""Not sure what all the fuss is about.""

Its called being "50", and just to sore and tired to jack up the car, crawl under it, and wrench the tank off then taking a bath in the fuel as it spills out...plus, an all day adventure in the art of BS, im sure

Prop
Prop and the Blackhole Midget

50 Prop? lol. You're still in nappies(diapers to you). Ha ha ha.
Lawrence Slater

50? I'm about to attempt it at 68!
Graeme W

hi graeme. i have a brand new sender for a mkii i may sell if you need one. ibought it for my car from moss but when i fitted it the reading was no different so i put the old one back. it turned out that i had the wrong gauge. let me know if your interested. bob.
bob taylor

Bob: thanks for that but I think it's different from the one fitted to a frog. I have looked in several supplier's catalogues and they list different part numbers.
Graeme W

graeme. the one i have is list number. 21a168
bob.
bob taylor

Apologies Bob! The Moss catalogue shows a different part no for Mk1 and the part you quoted for Mk2 sprite/Mk1 midget onwards. But if you clcik on "info" next to the mk1 item it says "no longer available use 21a168!"

I would like to get the tank down to see what the problem is but if I do need top buy one I'd be happy to talk to you about it. Do you want to email me at "myfirst name"at kingshillcad dot "the usual" just to establish communication?
Graeme W

Graeme,

68, ouch...I dont envy you, how many Tylenol are you going to eat like candy that day....hahaha

Prop
Prop and the Blackhole Midget

Prop: it just limits how long I can spend struggling in difficult spaces. Usually only a couple of hours although sometimes it can be much longer (usually because I am stuck and can't get out).
Graeme W

This thread was discussed between 02/11/2014 and 05/11/2014

MG Midget and Sprite Technical index

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