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DB18-1 Petrol Reserve Tap

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Frankie&Ollie
Posts: 6
Joined: Mon Mar 25, 2019 7:21 am
Location: Poole, Dorset. UK

DB18-1 Petrol Reserve Tap

Post by Frankie&Ollie » Wed Jul 10, 2019 6:45 pm

Our DB18 has fuel in tank but none is reaching carb. We think it's the Petrol Reserve Tap seals (have seen similar posts here which indicate this).
Does anyone have a diagram that shows how it fits and comes apart please so we can try and replace seals or by-pass all together?
Thanks
F&O

thomas@prags.co.uk
Posts: 21
Joined: Tue Sep 11, 2018 11:37 am
Location: Inverness

Re: DB18-1 Petrol Reserve Tap

Post by thomas@prags.co.uk » Wed Jul 10, 2019 11:05 pm

me too please - assuming its the same as on my 49/50 DB18? I remember replacing the cork about 40 years ago but can I remember what I did ..?!
Derek Sleigh thought a sticky seal might be causing a fuel feed issue - leading to my backfire issue - and I think he may be right - pulled out the reserve knob and it seems to be running without banging away!

Peter Grant
Posts: 184
Joined: Thu Mar 10, 2016 10:02 pm
Location: Sydney, Australia

Re: DB18-1 Petrol Reserve Tap

Post by Peter Grant » Wed Jul 10, 2019 11:58 pm

Hi,
On both my cars (Special Sports) and DE 36 the fuel reserve has been removed and the lower line linked tot eh fuel pump with the upper line securely blocked at the fuel pump end.
The DE was like this when i bought it but the Special Sports suffered from no fuel coming through and after removing the reserve tap it has been faultless.
Access in the garage was difficult, but if you could put the car on a hoist that would, i think help hugely.
Sorry can't give advice on best way to dismantle except to say use great care as the components are quite fragile. New corks are available from both John Nash and David Beales.
Cheers
Peter Grant.

Frankie&Ollie
Posts: 6
Joined: Mon Mar 25, 2019 7:21 am
Location: Poole, Dorset. UK

Re: DB18-1 Petrol Reserve Tap

Post by Frankie&Ollie » Thu Jul 11, 2019 7:12 am

Thanks Peter,
now we know which line to connect and which to block off!
Will give it a go and see what happens, fingers crossed.
Regards
F&O

qantasqf1
Posts: 115
Joined: Mon Mar 07, 2016 10:13 pm

Re: DB18-1 Petrol Reserve Tap

Post by qantasqf1 » Fri Jul 12, 2019 2:30 am

Replacing the 2 cork seals of these fuel valves is pretty easy. Once the valve has been removed from the car you’ll find a small slot-headed stop screw threaded into the brass body of the valve. You can’t miss it! Undo this screw and the plunger complete with cork seals can now be withdrawn from the body. The 2 seals are separated by a brass distance piece, and each seal is supported by a brass sleeve fitted to their inner diameter. To release the seals you’ll find a tiny grub screw threaded adjacent to the plunger’s tip - this locks a long screw which passes through both seals and screws into the plunger’s tip. Remove the grub screw and the long screw can be undone, thus releasing the seals. Refitting is the opposite etc etc...
I found it useful to deliberately leave the long screw loose so the seals aren’t compressed, thus allowing the plunger to slip into the body without damaging the seals. When the plunger is all the way home a small screwdriver inserted through the hole at the base of the housing can be used on the long screw to tighten it up. ‘Feel’ is important here because over tightening will make the valve tight to operate. When that’s done tighten the grub screw and refit the slot headed stop screw. Soak the cork seals in light oil before fitting.
Clear as mud, or would it help if I took some photos?

thomas@prags.co.uk
Posts: 21
Joined: Tue Sep 11, 2018 11:37 am
Location: Inverness

Re: DB18-1 Petrol Reserve Tap

Post by thomas@prags.co.uk » Fri Jul 12, 2019 8:40 am

thanks - the key bit of info is to remove the whole thing and not try and do it in situ! I had a vague recollection of doing the latter 40 years ago.
thomas p

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