Fast Marina Magazine

Ok! Here's one for the Techies on here.
This might have ben covered before but need to replace my sender unit and was wondering. From memory the sender units were quite simple, a float and arm operating a wiper, moving over a resistance wire set up, enclosed in an Ali. box.
Now my knowledge of electrics is that rheostats have a habit of sparking and with all that petrol sloshing about surely there would be a tendency for tanks to go bang - but dodn't, obviously.
Is this because the rheostat is liquid proofed, because for ignition Oxygen is required and somehow Oxygen is forced out of the tank by fumes etc?
Any ideas anyone? Apologies if this is a stupid question!

And just to be further surprised - some cars have their electric fuel pump inside the tank!

I am guessing it all has something to do with low voltage, Oxygen to Petrol Fume ratios etc!

Don't try this but if you put a lit match in a bottle of petrol after just removing the bottle cap the petrol will put the match out. Wait that bit to long though and you will need a wig and eye brows etc at the very least.
It is just petrol fumes which are highly combustible.
You see all those You tube clips of people sloshing petrol on a bonfire and then come back a moment later with a match and boom! the fumes have built up enough to become explosive which also sets fire to the trail of petrol they have not noticed they spilt all round their garden probably leading in to their garage!
So I assume a spark in a resistive winding sat in petrol will also not ignite. Its been that way for many years with no issues so should be fine and they are not sealed from petrol.
To repair the resistive winding you need the same gauge resistive wire and same amount of turns and assuming the wiper is still serviceable and not also worn through. they normally wear in the middle part of the winding.
I was thinking about doing mine but just bought a new one as the winding ends are sort of riveted from memory but I am sure doable.

There is no Oxygen inside a fuel tank hence no combustion. Fuel vapour is heaver than air and expands more when warm so the air including the Oxygen is pushed out of the fuel tank breather. Almost without exception modern cars the electric fuel pump runs inside the fuel tank the fuel also cools this, I have even seen a dry soldered joint causing a breakdown without a explosion. Removing this fuel vapour is very difficult even on a empty tank why it is so dangerous to weld a fuel tank. Fuel tank units are fairly available so trying to repair one is not very cost effective However the resistance winding is common with most British cars of the era as they almost all used Smiths gauges notable exception is Vauxhall as GM fuel gauges worked backwards
Dave

Pretty much wot I thought:)
I might have a go repairing the original sender unit once I fit a new one as I can manage most fixes. If the wiper arm is worn I will try to make a new one.
Easy to check resistances of windings and the wiper.
At the moment my fuel gauge is a piece of dowel dipped into tank down the filler pipe:)

From my experience, the wiper doesn’t wear through, it’s the windings that break due to wear by the wiper.

https://www.ebay.co.uk/itm/30397037742 ... %3A2332490

Maybe one of these sort of things could be adapted if supply is running low?

Given the likely costs of buying and then fitting one of these, why not buy a genuine OE sender from the owners club. It will fit perfectly and read accurately.

MarinaCoupe wrote:Given the likely costs of buying and then fitting one of these, why not buy a genuine OE sender from the owners club. It will fit perfectly and read accurately.

Have already contacted "balmy" to buy one.
But when I have the old one out am thinking about refurbishing it - to see if I can

Sent from my SM-J330FN using Tapatalk

MarinaCoupe wrote: Mon Aug 02, 2021 11:06 am Given the likely costs of buying and then fitting one of these, why not buy a genuine OE sender from the owners club. It will fit perfectly and read accurately.

Aye I didn't know there was a supply of new replacements but it's always worth investigating options for if and when bits dry up which I've no doubt the club investigates as tome goes by,,stuff like blow moulded HDPE fuel tanks,,ABS vac formed wings etc is always the kind of things I postulate about.

I have kept all my broken ones. I have had NOS ones which have only lasted a year or two so it's no guarantee. All you'd need to do is calculate the number of windings and somebody with a coil winder (anybody who makes transformers basically) would be able to rewind them. Not sure on cost. The last mains transformer I had rewound was around £70. As it's less work/material it should cost less.

We have a solution already in place for when the NOS senders run out involving an readily available sender that only needs slightly modifying to fit.

Hiya Balmy

Do you still have any Fuel Tank Sender Units available and if so how much?

Regards

Adrian

Use a Range Rover one (part number PRC4510) - needs a little modification to the length but you can use your old one as a template.

That's cool:)