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Locking filler cap won't unscrew


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I have a locking filler cap on the diesel filler, and discovered on Saturday that I wasn't able to undo it. Locked or unlocked, the cap just spins freely without unscrewing. In the past there was always a fair amount of resistance when screwing or unscrewing it - it now turns freely and continuously in both directions. I haven't had a chance to take a proper look yet - hoping someone here might have some previous experience? Is there likely to be an 'external' solution, or am I going to need to need to gain access to the filler pipe from the inside?

 

I've tried to upload a photo of the type but my Internet is shocking at the minute, so no joy. It's a similar type to this, but not an exact match.

Edited by tehmarks
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We have one of them, it is always difficult to screw it back down. There was a time when it would just keep spinning but it always seemed to undo eventually.  I took the cap apart and it has been a bit better since then but I'm thinking of replacing it.

Edited by Rob-M
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5 hours ago, Flyboy said:

I think you will need to post a photo before anyone can help. The one shown in the link has a flap so doesn't unscrew like yours.

FWIW the one in the link - which it turns out is not what the OP has - does unscrew. The flap covers the keyhole, and once unlocked the whole shiny bit unscrews. The one in the link couldn’t end up going round and round as described by the OP.

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In default of trying anything else - how about lifting the cap while turning it?

The threads between the cap and the fitting may have come out of alignment and may no longer be in contact?

Seems daft - but you never know... 

  • Greenie 1
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I had the same problem with a locking cap, and it turned out that the cheap nasty locking mechanism had broken, leaving it locked in the free spinning position.  It sounds like yours is doing the same.

 

In my case the owner of the boatyard I was trying to fill up at spent about an hour upside down unbolting it from underneath. 

 

When he eventually got it free, I said "Stick a fiver's worth in please."  He looked at me with a rather pained expression!

 

(When I stopped laughing at his expression I got him to fill the tanks - I'm not quite that cruel)

 

 

These caps are only meant to stop casual theft - they aren't very secure.  As a quick workaround, you should be able to prise the cap off with a long bar, but this will destroy the fitting.  If you aren't desperate for diesel, buy a new cap first just in case forcing the old one leaves you without a rain over for the tank.

 

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4 minutes ago, TheBiscuits said:

I had the same problem with a locking cap, and it turned out that the cheap nasty locking mechanism had broken, leaving it locked in the free spinning position.  It sounds like yours is doing the same.

 

In my case the owner of the boatyard I was trying to fill up at spent about an hour upside down unbolting it from underneath. 

 

When he eventually got it free, I said "Stick a fiver's worth in please."  He looked at me with a rather pained expression!

 

(When I stopped laughing at his expression I got him to fill the tanks - I'm not quite that cruel)

 

 

These caps are only meant to stop casual theft - they aren't very secure.  As a quick workaround, you should be able to prise the cap off with a long bar, but this will destroy the fitting.  If you aren't desperate for diesel, buy a new cap first just in case forcing the old one leaves you without a rain over for the tank.

 

I'm struggling to buy a replacement that will fit, I tried all the brass caps in Midland Chandler's and they were all too small.

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2 hours ago, OldGoat said:

In default of trying anything else - how about lifting the cap while turning it?

I've given all of the common sense solutions a go (well as best as I could while perched between my gunwale and NB Alton!) - pulling and screwing, pushing and screwing, kicking in, pulling, both permutations of key positions - nada. I'll see if I can get any further once I'm pointing the other way - but at the minute I'm waiting for post on a visitor mooring, and winding will put the solar at the shady end.

2 hours ago, TheBiscuits said:

When he eventually got it free, I said "Stick a fiver's worth in please."  He looked at me with a rather pained expression!

?

14 hours ago, AndrewIC said:

FWIW the one in the link - which it turns out is not what the OP has - does unscrew. The flap covers the keyhole, and once unlocked the whole shiny bit unscrews. The one in the link couldn’t end up going round and round as described by the OP.

Mine unscrews too - or rather, it should, leaving you with the whole shiny cap in your hand when it's undone. I don't fully understand how the locking mechanism works - which is a definite disadvantage when trying to remove it!

 

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31 minutes ago, tehmarks said:

I've given all of the common sense solutions a go (well as best as I could while perched between my gunwale and NB Alton!) - pulling and screwing, pushing and screwing, kicking in, pulling, both permutations of key positions - nada. I'll see if I can get any further once I'm pointing the other way - but at the minute I'm waiting for post on a visitor mooring, and winding will put the solar at the shady end.

?

Mine unscrews too - or rather, it should, leaving you with the whole shiny cap in your hand when it's undone. I don't fully understand how the locking mechanism works - which is a definite disadvantage when trying to remove it!

 

I couldn't quite workout how the locking mechanism worked even when I had it apart.  It looked like it slightly moved the alignment of the top thread.

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The locking cap has a couple of thin pins or lugs that fit into recesses inside the threaded bit.

 

When the cap is locked, these retract so you can't unscrew the threaded bit. 

 

When it's unlocked the lugs engage allowing you to twist the thread with the part of the cap you can get hold of.

 

If the mechanism is broken, you can't unscrew the cap without breaking the top cover off and using a wrench on the threaded bit.

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I had one of these that did exactly the same....I ended up using a cold chisel/ bolster and large hammer...totally destroying it in the process...I wasn't happy given that it wasn't a cheap unit...I think the plastic reacts with diesel...the threads on the cap are plastic...shame because brass locking caps are really hard to find unless someone knows different. I should have complained to the supplier as I hadn't had it long but I never did. 

Edited by frangar
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Thank you all for the great advice. Unfortunately fate has conspired against me - I winded and moved on, and now I'm on a mooring with the towpath on the other side of the cut - so the bloody thing is still on the off side. I'll take a loo at it in the next few days, and report back in the unlikely event that I discover something useful for future persons with the same problem. I'll give hammer-tapping a go, else I'm afraid I'll probably move straight to taking a cold chisel to the lock.

 

Boats! Who would buy one? ??

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12 minutes ago, tehmarks said:

Thank you all for the great advice. Unfortunately fate has conspired against me - I winded and moved on, and now I'm on a mooring with the towpath on the other side of the cut - so the bloody thing is still on the off side. I'll take a loo at it in the next few days, and report back in the unlikely event that I discover something useful for future persons with the same problem. I'll give hammer-tapping a go, else I'm afraid I'll probably move straight to taking a cold chisel to the lock.

 

Boats! Who would buy one? ??

I had to put the cold chisel between the lid & the deck fitting....you might want to get a replacement deck filler before you get too carried away. 

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