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MG MGB Technical - Thread size on early tank sender

I have bought a new sender for my 1964 MGB tank. It's defective. As it came via Ebay and from the USA, I reckon I'm stuck with the thing.

Unfortunately one of the screws that holds the cap on has stripped threads. There is a bit more thread at the bottom of the hole but the screw is too short. Can anyone tell me what size thread the screw is please? I can then get a longer one and it should be possible to fasten the lid down tight.

It's the screw for the lid rather than the one that holds the whole thing to the tank.
Mike

OH, I am in need of a new tank sender unit also. So don't get them from E bay your saying? Right. Is it too small for a helicoil? or one of these putty mixtures that are hard enough to cut a thread on after they are set? Mike
J.M. Doust

Mike, get your old one repaired! It's the best solution. Really! I've tried several with no luck so far. The first one stuck at low tank levels (when you need it most!). This one leaks because there's no thread on the screw hole. It's one of these never ending stories.

There's a bit of thread at the bottom of the hole, enough to grip when the lid and gasket are off. I hope to use a longer screw. I'll try helicoil or putty as the next solution.

I would have expected a BA thread but the diameter and pitch of the thread seems odd.

Outside diameter: 3.4mm
Pitch approx. 1.75 threads/mm

I need to get one of my boys to look at the thread with sharper eyes than mine!

Mike
Mike

I don't think Mike is saying don't get the item from eBay. My new sender from the US arrived last week and I have fitted mine with no problems. It came from NOS Locators or some name like that. It seems to work correctly through the range when I tested it outside the tank. I have not driven with it yet because I am about to refit my fuel pump. The quality of the item I received seemed very good and was very easy to fit.
I don't know what the thread size is but I think they are a BA thread.
Ian
Ian Buckley

Sacriligious I know, but is there a modern day digital equivalent of a tank sender? I cannot imagine how it might work, but surely there is a 'nerd' out there with the knowledge and expertise? Mike
J.M. Doust

Not more 'pointless' electronics perlease!
PaulH Solihull

I don't think they are electronic but they have 2 arms wiping the coil; one either side I believe. It is early days yet but mine seems to be more stable than my originals.
Ian Buckley

The original has one arm wiping the side of a coil, and it's usually the arm that gets tangled up in the winding, so two arms is double-trouble! The MGB is well known for having a non-linear gauge, despite the sender winding having a three-stage construction in an attempt to limit it. But a Toyota Celica I had would do 70 miles before coming off F, then when I parked up it would 'lose' another gallon or so. At least with the MGB I know that it will read higher after a left-hand bend and lower after a right, I've not yet managed to work out what causes the ZS to go up and down (at least, to go up. I know what makes it go down!)
PaulH Solihull

Guess I'll have to continue using the dipstick! Mike
J.M. Doust

I always fill the tank and reset the tripmeter. It is a hard habit to break and comes from my motor cycling days. There is nothing worse than reaching down to turn on the reserve tap to find the tap is already on reserve.
Ian Buckley

Mike: The digital equivalent of the tank sender is petrol=1, no petrol=0! 1 works, 0 doesn't work.

I've taken the first replacement (that sticks from 1/4 full) to pieces and it has a single wiper. The single wiper pushes the shaft (on which the float is attached) a bit too hard and makes the arm stick as the tank gets emptier. I am looking for a fine washer to space the arm out from the pivot in the hope this improves its movement.

The shop in the USA that sold me the sender with the stripped thread suggested I send it back, so I'll try that.

So I'll see if I can get the first replacement working or make up a blanking plate.
Mike

"is there a modern day digital equivalent of a tank sender?"

Well blow me if there isn't exactly that in the MGOC July Enjoying MG, comprising 'thick ceramic tile with printed silver conductor' rather than a winding. An all-plastic body rather than the metal disc clamped between the locking ring and the rubber gasket, and the earlier version i.e. not the one with the fuel outlet. Not shown on the online parts list but shown in the mag as part number AHU1027Q at £15.95, 01954 230928. Only a quid dearer than the original.

I wonder how long the silver conductor will last with the wiper rubbing up and down on it all the time ...
PaulH Solihull

This thread was discussed between 27/06/2011 and 01/07/2011

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