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MG Midget and Sprite Technical - Best way of cleaning out a fuel Tank

I'm currently working on my Cousins mgb roadster which hasn't run for about 7 years - been started a few times.
When I checked it out no fuel could be pumped from the tank (it has a 90deg connection into the tank) so I connected up a big old heavy foot pump and after a bit of pumping it blew clear back into the tank and I got the old girl running ! - the electric fuel pump has a cork gasket to the air chamber and that had totally swollen up and fallen into a large crumble mix as well !

So i need to clean the tank - It dosn't seem to be rusted - I fitted it about 20 years ago and it was well protected with paint and waxoyl. I guess the block is stale fuel and sediment gum etc - the stuff that came out of the angled connection was rather thick / black goo.

So I will drop the tank and keep flushing petrol through it (sender will be out as well for replacement) I can pump air into the outlet to assist and I thought about injecting carb cleaner through the outlet and blowing back through.

I have just ordered up all new flexible pipes for the carbs and will work my way forward from the tank.

Any other ideas to clean the tank out ?

I know its a B but tanks are tanks and this board has lots of experience in solving all sorts of problems !

R.
richard b

Petrol is expensive Richard!
Since you have the tank out and the sender removed I'd be tempted to try a couple of pints of red diesel first and perhaps a good wash out with soapy water as hot as you can get it.
Does the fuel pipe and strainer come out of a Bs tank in a similar way to the midgets? Can you access it through the sender hole? IDK - I've never seen one in the metal. If so it would be good to have a serious look at the strainer.
As said, I've never seen one so it's speculation at best.
Greybeard

Thanks Greybeard - actually I should call myself 'Whitebeard' !!!
Petrol is free ! there is probably 5 gallons still in it - I was going to keep flushing a quantity through an old not linty sheet (linen ?) sheet - I've done it before on small yachts that have had problem with diesel (one had a copper tank !).

Did think if all else fails of trying a water blaster (Karcher type thing) but unsure if the filter would be damaged.

I don't think the 90deg elbow into the tank is removable. Need further investigation.

R.
richard b

Richard

Anything useful here in terms of tank cleaner and sealants:
https://www.frost.co.uk/fuel-tank-repair/?gclid=Cj0KCQjw3qzzBRDnARIsAECmryrkc8uP8aBU4heImlDlyVGARkvsr2FiKfLWw3RTfKz3QGZNEt-xYVEaAvSgEALw_wcB

Also thinking about the possible intro of higher ethanol content of fuel perhaps a chance to use a more ethanol resistant sealer. Anyone tried Tapox?
https://fertan.com/product/tank-coating/tapox/ & https://www.britishbikebits.com/fertan-tapox-ethanol-proof-petrol-tank-sealer

Cheers
Mike
M Wood

I can endorse the Frost kit, comprising cleaner, rust remover, and sealer. It did a great job 15 years ago and the sealer is still perfect.

Reminds me of a story I had on good authority many years ago. A chap needed to weld a petrol tank, and was concerned about vapour left in after draining. He decided to suck it out with a cylinder vacuum cleaner. You have guessed the rest. The vapour ignited when it reached the motor and the cleaner shot across the garage, trailing the remains of the hose like a wire guided missile.

Les
L B Rose

The problem with sealers is that I don’t think the ‘in tank’ filter can be removed !
So currently cleaning is the only option other than replacement.

R.
richard b

I got curious so I did some searching and reading and it looks like you're right about the in-tank strainer.
It seems there are two basic types of tank - earlier rounded ones mounted by straps and later squarer types bolted up to the boot floor.
They have different senders in slightly different positions but otherwise similar construction.
There are two longitudinal baffles and the pick up pipe passes through a hole in the right side baffle into the middle of the tank, with a small strainer on the end which looks like it cannot be removed without cutting the tank open.
So, very difficult to clean the strainer and anyway if the tank were treated with a sealant inside it would be liable to block off the strainer altogether.
Also from what I can see it seems you're right again about the right angle connector on the side of the tank. It seems to be welded/brazed/soldered (??) in position which is a bit of a bugger.
US spec tanks turn out to be a bit different. The sender and pick up arrangements seem to be the same but the left baffle is omitted and replaced by a clever delayed fill device designed to prevent fuel being blown out of the breather from fluid expansion in warmer environments. It's the reason that US tanks are rumoured to be smaller - they are actually the same size but the delayed fill device makes you think it's completely full earlier than a tank without one. If one were to fill it then leave it twenty minutes it's apparently possible to put an extra couple of gallons in.
Here's an image of the the cutaway car at Gaydon that shows the pick up in the volume between the baffles, in the middle of the tank.
There's loads of pictures on the MG Experience site where people have cut open the tank to fix them. They are mainly from American posters so they show the delayed filler, but the tanks are otherwise similar. I just googled "mgb fuel tank" and clicked Images and found loads of information.



Greybeard

This thread was discussed between 13/03/2020 and 14/03/2020

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