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Bishopgray have recently done an excellent job refurbishing the Autovac on my 2 Litre High Chassis but this has now revealed that the main/reserve fuel switch (picture attached) is leaking as the internal cork gaskets have reached the end of their life. They are 3/4 inch diameter and one is maybe 1mm thick and the other around 6mm.
I was wondering if anyone knows anyone that supplies replacement gaskets for this application ( I think that the club ones are a lager diameter) or a supplier of a suitable material (nitrile rubber ?) from which I can make some ? If anyone can confirm the exact initial thicknesses that would also be useful as its difficult to tell from whats left of mine.I’ve the same problem and have (temporarily I hope) replaced the elegant original switch with one of the commercially available Enots c/o taps. It does the job but looks very wrong. Have you had any responses or suggestions? It seems odd that the corks for the larger tap are readily available but not for the one used on the 14/60 and Speed models.
Hi gentlemen,
I have my fuel system down presently and am also considering the condition of this valve. Did either of you solve the problem of gaskets?
Thanks
GrahamHi gentlemen,
I have my fuel system down presently and am also considering the condition of this valve. Did either of you solve the problem of gaskets?
Thanks
GrahamI would suggest that you might try contacting Bishopgray and see if they can help you.
There is another potential issue with the fuel switch in that the internal hole diameters are slightly too small and can restrict fuel flow particularly when running for long periods with large throttle openings such as on a Motorway….. which probably wasnt a big problem in the 1920’s ! While you are working on the switch, unless this has already been done, it might also be worthwhile trying to see if you can get the holes enlarged.
Lagonda1928 wrote: I would suggest that you might try contacting Bishopgray and see if they can help you.
There is another potential issue with the fuel switch in that the internal hole diameters are slightly too small and can restrict fuel flow particularly when running for long periods with large throttle openings such as on a Motorway….. which probably wasnt a big problem in the 1920’s ! While you are working on the switch, unless this has already been done, it might also be worthwhile trying to see if you can get the holes enlarged.
Thanks for this. Graham
Wondering whether anyone has cracked this? My fuel switch is making a great hissing noise and my car seems to be searching for fuel. I suspect an air leak but am reluctant to strip the switch unless new seals can be found from somewhere. Thanks for any update.
Hi John, which switch do you have? IF it is the one that sits on top of the glass bowl then your only solution is to lap it in. These seal by a interference fit and over time the brass wears and allows air into the fuel system. The pressure on the tap is maintained by a small spring underneath held in by a washer and split pin. Worth checking this is OK and actually pulling the tap down.
A second thought is regarding the hiss. On the old LP SU pumps the pressure is not usually enough to make hissing. Do you have a modern petrol pump?. If so you might want to put a pressure regulator in to reduce the pressure.
Thank you Len for your reply. My switch is as per the photo earlier in this thread and from what I can tell the upper inlet pipe is main tank. I have a brass zenith filter downstream from the switch en route to the auto vac although I think the actual filter element is disconnected: I have inline modern filters in the lines closer to the tank.
I’m not sure whether the toggle switch engages main when up or down but hissing comes from the switch in either position. Although not if I leave it in mid-position. Not having dismantled the switch I don’t have any clear sense of how it works. Any enlightenment very welcome! Thanks again. JohnSorry John I didn’t see the earlier thread. I think I have one in my box of useful bits. I’ll take it apart and photograph the internals for you – an me!. Making up cork gaskets shouldn’t be too difficult. I have various thickness cork sheets and plenty of hole punches.
I’ll report back later today Len
Hi John,
I eventually found my diverter tap. I intend fitting this to my 16/65 which currently only has a main supply.
I’ve stripped mine down and you can see the dimensions in the attached photo. I measure the upper cork gasket at 3/32″ (0.09″) and the lower one 5/64″. Both are cloth mesh reinforced, though I don’t think that would be critical. Importantly I think are the 4 washers, 3 of which seal the inlet/outlet couplings and the larger one on the diverter tap retaining bolt/banjo are critical to the sealing of the tap assembly. If these are not sound they could easily cause leaks or let air into the system.
I have plenty of cork gasket but none these exact sizes, sorry
I think fitting nitrile rubber would be a good modern substitute and in fact probably better than cork. The key is going to be to make them exactly the same as the holes in them need to line up with the holes in the diverter tap. You could super glue them to the diverter fitting to make sure they stay in line.
Hopefully this is of help. Let me know if I can help further.
Len
John, I should have mentioned that the 3 washers for the inlet/outlet couplings are copper.
For info, the link below gives some advice on selecting the correct cork material.
“Generally speaking, if you’re making cork gaskets for sealing petroleum or diesel, you want to use a cork material with a Nitrile Rubber Binder (sometimes referred to by it’s short-hand code: NBR).” https://www.swiftsupplies.com.au/news/is-cork-fuel-resistant-it-depends-on-the-cork
It was a few years ago now, but as previously mentioned, Bishopgray refurbished my switch which included enlarging the internal hole diameters which at least on mine, were quite restrictive.
wow! This is fantastically helpful. Thank you both very much indeed. I will look forward to stripping this and finding out what state the various parts are in and will update. Maybe not immediately though as a little preoccupied with a different project first. Thanks again
John
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