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MG Midget and Sprite Technical - Seized lockable fuel filler cap?

Hi all,

I realize that I am an extremely occasional user on here, these days, virtually a tourist, but I have a query I could use some help with, if you don't mind.

I have a '71 Sprite with a lockable fuel filler cap. With the weather as it has been, it has been some weeks since I had to refuel the car, so the cap has not been off in a while. I fired up the car today, saw that the fuel was very low, so went to remove the cap and top up... and the key won't turn. It is obviously a pretty flimsy key, so I don't want to push my luck, but I am imagining that I have some surface rust in there, and it has just stuck. Does anyone have any tips for how to free this? Is squirting WD40 a good idea? Or will that do more harm than good when it dries?

If the worst comes to the worst, can I force the lock with a screw driver and buy a new filler cap? Or is there an important fact that I am missing that makes that a terrible idea..?

I would appreciate any advice anyone can offer, as locks and I don't really get on so I'm a bit stuck.

The car is garaged, and I fuelled it in February and the lock worked entirely normally then.

(I also have a friend with a seized clutch on his '70 midget, I said that I would ask on here if anyone has any thoughts on that that don't involve removing the engine to get at the clutch? His has stood for six months, being fired up but not driving, so I fear his seizure issue could be somewhat worse than mine... I did look in the archive for both issues but could not find anything, apologies for wasting your collective time if I simply missed it)

Thank you in advance for any help on either issue (obviously my fuel filler cap being the far more important one lol) and apologies for being such a part-timer here this year, small children have taken over somewhat.

Piers Colver

I recently had a problem with a lockable filler cap. It was made worse by the fact that i din't have a key for it.

I bought a replacement fuel filler neck which came with the lockable cap. Having tried all of my spare keys, I couldn't find one to open it, so I made myself a lock pick from a piece of welding rod and set about opening it.

Having spent ages trying to open it without success, my other half suggested some WD40. I tried some WD40 and it was open within a couple of minutes. I then discovered that one of my spare keys would have opened it with a bit of a wiggle, but as the levers in the lock were partially seized, it wouldn't.

A long winded way of saying - Yes, try some WD40 or other lubricant.
Dave O'Neill2

You can fill up the tank using a temporary work-around, by undoing the jubilee clips on the rubber hose inside the boot and uncoupling the metal filler pipe.

Care needed of course, e.g. remove bulb from the boot-light if you have one... you don't want any sparks...

Anthony Cutler

Get some Tri-Flow lubricant for the lock. It's a liquid and will seep into the lock and should work to release the key mechanism. Recommended by professional locksmith to me for use on my cars and it does work well.
Good preventative maintenance for all your locks and keysets.

B Young

Halfords have a similar product with PTFE
Dave O'Neill2

WD40 will do the trick...
P Ottewell

I once lost my filler cap key on a club run and had to resort to the method mentioned by Anthony. Personally I think that WD40 is least effective as a penetrating oil, better to use something like Plus Gas.


b higginson

Never use a lockable full cap!
Far to irritating and risk of freezing solid in winter put me off those years ago
Onno K

But with the price of petrol now, the siphoners are back, --- if you park outside overnight. So maybe as lockable is still worthwhile.

I find a lockable useful for another reason.

I leave the keys in the fuel cap when filling up. If I then forget to put the cap back, -- as I've done in the past, when I didn't have a lockable, -- I can't drive away until I get the keys out of the cap, which reminds me to put the cap back.

To be truly honest though, I'm not sure if lockables are really any good. A screw driver rammed down the slot, and a quick twist will remove most of them pretty quickly. I've done that too.
Lawrence Slater

Had a spare filler neck in a box of bits for several years but even though we could have used it previously I always shied away from it because of the locking filler cap that was on it and the fact we had no keys.

Nev's new to him Midget came with the same type of locking filler cap and obviously some keys so I thought it would be a good idea to see if his fit mine.

Now, the thing is.... if I'd actually tried to remove the cap years ago I would have found that it actually wasn't locked and a simple turn of the cap would have released it... but not me... my logic says that a locking filler cap will be locked onto the neck, but not this one.

Andrew McGee

So that's enough to deter the petrol thieves then. Doesn't have to be locked, ---- just lockable. :)
Lawrence Slater

Don't forget that the thieves don't need to siphon or break the cap. They just need the right spanner for the drain plug!

b higginson

Assuming that your tank has a drain plug. Most of the replacements don't.

My colleauge's wife couldn't start her car one day. She knew she had petrol as she had filled up the previous day, so she called the AA.

AA man turned up, looked underneath and said "you've got no petrol tank". It had been stolen!
Dave O'Neill2

thiefs just cut the pipes from the tank to get the fuel

I remember a chap who got an item (can't remember what starter, alternator) stolen off an old banger and it seemed strange as it would have been an old worn part

next week they stole the new replacement part - it then made sense

new central heating boilers used to get stolen from new build houses (they steal everything now sometimes leaving water leaking everywhere) they then waited for the replacement

same as when they used to steal VCRs from people's homes they'd wait for the insurance replacement VCR
Nigel Atkins

sorry thieves not thiefs
Nigel Atkins

Very true about the heating boilers, I knew a builder that happened to. He was hoping the t leaf would come back for seconds, so he could fracture his skull. Alas, the thief didn't come back.
Lawrence Slater

it's all very true Lawrence

but don't ask me how I know :)
Nigel Atkins

You haven't got a second career as a petrol/boiler/ car parts thief have you Nigel? And there's me thinking you were a good Church going pillar of the community.

b higginson

He could end up as a pillar on a motorway flyover if he got caught Bernie :)
Lawrence Slater

who sezs it's a second career

pillar no, something else yes and I don't do any sort of religion, not sports, celebs, or hero-worship of people or marques or models and as I also dont do wedding using wedding cars tonbridges or funerals Im very unlikely to be going to a church

unless its for a nice cup of tea and cakey :)
Nigel Atkins

Nige. Unfortunately there WILL be one funeral you'll go to, but you won't know you're there! LOL.

Bernie :)
b higginson

A vote here for gt85 - available from most bike shops, or bike department of Hafrauds. WD40 will work, but evaporates in a few days. The fuel vapour does dry out oils quite quickly
d cusworth

Just wanted to post a belated follow up to this, with thanks for all the advice.

I pumped the lock on the cap with WD40 - the red straw that comes with it fits in the keyhole! - and left it overnight. I awoke the next morning full of optimism... still stuck and did not want to risk snapping the key. Being an eternal optimist, I gave it a further dose of WD40, then again at lunchtime and a third lot that evening. The following morning I tried again and... it opened!

So a lot of thanks to everyone who contributed advice. I realize that all cars are different but basically I gave mine 36 hours of soaking and that freed it without needing the sort of force that would snap the key.

And I have now added regularly removing the filler cap to my list of regular winter checks.

Many thanks again to everyone.

Piers Colver

well done Peirs I often preach a good releasing/penetrating fluid (not usually WD40) and patience but the macho boys want to get a flame to it the problem - would have been interesting on a petrol cap

as you've found cars that aren't regularly used pick up problems and just starting the engine without driving the car doesn't help with many aspects and can even introduce problems if not run for long enough

just noticed we all missed your friend's clutch problem, did he get it sorted, a stick holding the clutch pedal down overnight seems a favourite, this is another problem from just running the engine and not driving the car
Nigel Atkins

The problem is of course Nigel there is a technique suitable for all problems unfortunately there is no silver bullet.

This is probably the best example of a situation where liberal amounts of "solution" was the best option for the problem

IE it was not stuck due to excessive corrosion but was just a build up of dirt and crud. Thus a soluable liquid was the correct idea.

Now when a bleed nipple has broken of and is corroded into position no amount of fluid will give the ability to rescue the situation.

On other occassions a quick flick with a welding gun saves hours of painstaking application of whatever penertrating fluid you chose to use.

Bob Turbo Midget England

yes if you have a welding gun possibly no need for patience, surprising as it may seem many of us don't have welding equipment in the shed or know others that do

but as you say more than one way to skin a cat

I'm sure a welding gun would have resovled this problem very quickly :)

I noticed you didn't object to the macho description :)
Nigel Atkins

@ Nigel hi yes thank you for the help, I don't have any welding equipment and the thought of that made me a little nervous so I decided I'd give it a week and see. Was relieved to see that slow and steady won the race on this occasion!

I absolutely hear you about not simply starting the car up in situ if one wants to head off all the storage issues. Trouble is, we get pretty heavy snow drifts up here, I have to dig my way to the garage (!), and once I have been unable to get the car out for a couple of weeks I just get into a lazy rhythm and tend to go with the 'fire it up in a warmish garage' option. But no more, I have learned my lesson and, mercifully, it was a pretty pain-free lesson.

Chris, on the other hand, still has no clutch and is now eying having to have the clutch out, which I think is an engine-out job, which he can't do himself..? He is a little blue about it, but oddly enough does currently have his clutch depressed with a broom handle and is praying to anyone who will listen that that sorts it. He is not optimistic, though, and tbh nor am I...

Anyway, thank you for the feedback, and I have learned my lesson and will move the car regularly through winter from now on, not just fire up in the garage!
Piers Colver

I wouldn't worry about not moving a car in good condition for a couple of weeks or even a couple of months - though better would be a 50 mile run once a month and testing wipers, washer motor, heater motor, horn, etc

firing it up in a garage you'll have to leave it running for a good while to get the engine fully warmed, then the ocassion rev, that might just get the starting power back into the battery and test the thermostat but you've only really dealt with the engine not brakes, tyres, suspension, electrics, so on

have a look through the Archives or put up another thread for Chris's clutch as there are other methods that might help, some brutal sounding, but some people get them going after years of the car not moving from the spot

I think the stick holding down the clutch pedal should work overnight

clutch is engine out, unfortunately I'm certain of that

Nigel Atkins

Thanks Nigel - I might pass on the encouraging ideas from the archive, hoping that that works, before breaking it to him that the next step is something more expensively drastic!! Thank you for the tips, very useful and much appreciated.
Piers Colver

no problem

don't forget also running a car for a long time in a domestic garage needs lots of ventilation, carbon monoxide poisoning isn't a good thing to get

here a list of things better for lubricating than WD40 (which is good as a water dispersant)

∑ light oil
∑ (thin) spray lubricant
∑ penetrating/releasing fluid (such as PlusGas - WD40 isnít that good)
∑ carb cleaning spray
∑ silicone lubricant (for rubber and plastics)
∑ electrical contact cleaner
∑ anti-seize assembly compound (like Copper Ease)
∑ electrical sealing/protecting products (go find)
∑ all purpose grease (and gun)
∑ cheap small brushes - to apply Copper Ease, grease, ect.
Nigel Atkins

This thread was discussed between 18/05/2012 and 21/06/2012

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