Fuel Cap Seal

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Gannet
Posts: 776
Joined: Mon Feb 27, 2012 9:47 pm
Location: Cirencester

Fuel Cap Seal

Postby Gannet » Wed Jun 26, 2019 6:10 am

Fuel cap cork seal.
I like to keep my engines as original as possible, however the cork fuel cap seal is I believe, an area that could be improved without sacrificing originality too much. Surely an ordinary nitrile seal of similar dimensions would be much more long lasting and reliable? Perhaps it is because I overtighten the cap to ensure that petroil doesn't leak into the car when I take it to the seaside, which soon results in the cork being flattened.
However, does anybody know of the availability of a petrol combatible seal of dimensions 1 3/4" x 1 1/16" x 1/8" ? Or 45 x 25 x 4 mm? I would have thought that there would have been one in common use somewhere.
Thanks

Jeremy

Chris B
Posts: 5
Joined: Tue Jan 29, 2019 2:37 pm
Location: England

Re: Fuel Cap Seal

Postby Chris B » Fri Jul 05, 2019 8:00 pm

I agree with you. There's certainly room for improvement on the standard cork washer.

However, you'll be glad to know that you don't need to hunt for a specially dimensioned replacement.

You'll find that a standard nitrile o-ring works very well for that job and it will last for many years. An o-ring of 25mm inside diameter, with a cross sectional diameter of around 3mm is a snug fit and won't fall off.

The nitrile is tough and elastic. Stretch and roll it up over the thread. It will sit snugly and unobtrusively under the cap, creating a fluid and vapour tight seal.

Chris

Gannet
Posts: 776
Joined: Mon Feb 27, 2012 9:47 pm
Location: Cirencester

Re: Fuel Cap Seal

Postby Gannet » Sat Jul 06, 2019 2:24 pm

Thanks Chris, I think I will give that a go. Sometimes the best solutions are the simplest! Thanks for the suggestion.

Another cork sealing problem is in the fuel tap. What about an alternative polymer seal for that item? Any ideas anybody?

I have nothing against cork as a seal, but it is horses for courses. The most efficient glass bottle seal against leakage of volatile cleaning fluid is in my opinion, cork. I am also familiar with it in whisky and wine bottles!

Jeremy

Chris B
Posts: 5
Joined: Tue Jan 29, 2019 2:37 pm
Location: England

Re: Fuel Cap Seal

Postby Chris B » Sat Jul 06, 2019 5:18 pm

Glad to be able to assist a little, Jeremy.

Incidentally, some years ago I fitted both of my WSCL fuel filler caps with nitrile o-rings. Both are used quite regularly and and neither have leaked since. Post-modification you'll find there's no need to tighten the cap down hard. When you first try it you'll probably sense that firm finger tip pressure is all that's required to create a good seal.

The fuel tap seal problem that you mention is a little trickier to resolve. I've seen several inventive alternative "solutions" but some are hopeless and none seem to be as successful as the original cork!

I get the feeling that the difficulty might be because the Ewarts fuel tap designer made an early and reasonable decision to use a cork seal, and then designed the tap around it.

However...

There IS a way of retaining the standard cylindrical cork seal and having a fuel tap that doesn't leak. This is achieved by making a small modification to the existing Ewarts fuel tap. The mod works well and has a bonus advantage - because if you don't like the result you can easily reverse it.

So here's how it's done.

Dismantle the fuel tap and remove the cork retaining spindle in the usual way.

Find a brass bolt that's of similar diameter to, and at least 5mm longer than, the original spindle.

File or turn the head of the bolt down to create a disc, similar to that which is on the end of the original spindle.

Slide your cork seal on to this bolt, and then fit the bolt to the fuel tap's plunger assembly. You want the excess thread of this bolt to be projecting from the existing central hole in the fuel tap's operating knob.

Now spin a nut and then a locknut onto the projecting thread.

Finally, reassemble your fuel tap.

What you now have is an original Ewarts fuel tap with an external facility to adjust the cork seal. Tightening the external nut compresses the cork on its long axis. This compression makes the cork try to increase its diameter, thus producing a tighter fit in its housing. Thus no more leaks.

Adjust the bottom nut so that there are no leaks but not so tight that the tap becomes difficult to operate. When you're happy with your adjustment, tighten the upper lock-nut.

In the event that your modified Ewarts tap eventually develops a tendency to weep fuel again, just tighten your adjuster nut a quarter of a turn and the leak will cease.

How easy was that?

Like the fuel cap mod, the fuel tap is now no longer entirely original - but on the positive side I would venture to suggest that it's arguably better than original.

Hope this helps!

Chris

Sandro Picchio
Posts: 77
Joined: Tue Dec 06, 2011 3:33 pm
Location: Lago Maggiore (Northern Italy)

Re: Fuel Cap Seal

Postby Sandro Picchio » Sat Jul 06, 2019 5:37 pm

I am a fan of cork as a material, for oil, petrol, wine, whisky, grappa etc.
As suggested by John S.O.S., there is a way to rejuvenate fuel tap cork seals: when they are dry and hard, boiling them in water makes them inflate and become soft. I think this can apply also to cap seals.
One more tip - always from John - if you don't use the motor for long, leave the rejuvenated tap cork seal outside the tap in a plastic bag with some oil.

Hope this helps.

Sandro


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