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"Reserve" petrol switch.

Technical issues not related to a DLOC car marque, eg tyres, ethanol, other car makes, etc. and legal, political and insurance
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Stan Thomas
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"Reserve" petrol switch.

Post by Stan Thomas »

Like most early Daimlers, my 1931 model has a mechanical petrol reserve switch, of which the seal is now leaking due to the original cork having hardened (by modern fuel?). The seal itself is quite simple, being a 3mm or so thick disk about 40mm in diameter so can easily be fabricated.

However, can anyone advise what particular material to use in the light of modern fuel requirements etc. - and a source of supply please?

Simon Hyslop

Re: "Reserve" petrol switch.

Post by Simon Hyslop »

The following may be entirely incorrect but I offer it as an antithesis to the woes of modern petrol.
I thought/think that cork drying out is probably the major reason for cork seal failure. Burlen Fuel Systems still supply 'cork' for their SU carburetor seals and I can't say I've experienced any more or less failures in these seals in recent years than at any preceding time. The ones on my 10 have been there for about 8 years as have the ones on the Rileys. The motorbike people seem to be running on cork petrol tap seals and the various people who supply the later tap seals on Daimlers and Lanchesters all supply cork seals.

Maybe Burlen would supply you a square of material the same as they make their new seals from (I don't know, you'd need to ask them) but failing that, some good quality fine smooth cork sheet of the correct thickness, well cut and soaked would seem a reasonable starting point.
I think there may be potential problems with cork that is bonded to rubber or nitrile but it may be the bonding that is attacked by the constituents of modern fuel rather than the cork itself.
I suspect someone involved in the process of making these things will have stuck them in a glass jar of 95 octane and left them for three months. If they come out looking, feeling and acting as a piece that's new then probably the material is o.k.

Norfolk Lad
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Re: "Reserve" petrol switch.

Post by Norfolk Lad »

There is a report on cork gaskets with Bio Fuel which reports little change so cork comes out good,maybe it is the bio fuel attacking the fuel line and its fittings causing the hardness in the cork.
Guess you could use the same rubber now in the mechanical fuel pump which is supposed to resist bio fuel, as your seal is 3mm thick i would think it must be available on ebay or online .

Stan Thomas
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Re: "Reserve" petrol switch.

Post by Stan Thomas »

Thanks for your comments lads.

It appears that Viton ruber is formulated to be impervious to modern fuels - so I've ordered a small sheet of the thickness I require.

I to0 share your views that cork should be O.K. - but such is the design of my car that the reserve switch is the highest point in the plumbing from tank to carb - so inevitably, a cork seal would probably dry out fairly rapidly.

let you know how I get on.

Stan Thomas
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Re: "Reserve" petrol switch.

Post by Stan Thomas »

I sent for some cork from Australia,
As soft as the petals of a dahlia.
But bio fuel I could tell,
Soon caused it to swell,
So I had to conclude 'twas a failure.

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