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DB18 Fuel Pump

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Hedgie
Posts: 41
Joined: Tue Aug 16, 2016 8:33 pm
Location: Streatley, Berkshire, UK

DB18 Fuel Pump

Post by Hedgie »

I have a couple of questions about the AC Fuel Pump fitted to my early 1950 DB18 (see photo)
DSC00790.jpg
Chassis Number: 56049
Engine Number: 42200

1) I have a couple of documents which describe the Fuel Pump as being either an AC U Type-1524242
or an AC T Type-1524242
How do you tell the difference between the "T" and the "U". / Is there a difference?

2) Does any one know a supplier of Diaphrams for this Fuel Pump? I understand that old Diaphrams don't like modern petrol.

Many thanks for all helpful answers.

Tony

John Hitchins
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Location: Wellington Somerset

Re: DB18 Fuel Pump

Post by John Hitchins »

Plenty of fuel pump kits on Ebay.

grahamemmett
Chief Geek
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Re: DB18 Fuel Pump

Post by grahamemmett »

Tony, type U superseded type T and are interchangeable. The type designation U or T is cast into the body.
David Beales eBay shop has what you need.
Graham Emmett ¦ DLOC Chairman ¦ chair@dloc.co.uk ¦ 07967 109160
Northwich, Cheshire
DB18 1949 LCV522 (Yes that one with the P100s)

grahamemmett
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Re: DB18 Fuel Pump

Post by grahamemmett »

FA281E53-2CE9-4450-9334-B6956108A712.jpeg
Graham Emmett ¦ DLOC Chairman ¦ chair@dloc.co.uk ¦ 07967 109160
Northwich, Cheshire
DB18 1949 LCV522 (Yes that one with the P100s)

Dartford Dave
Posts: 44
Joined: Fri Jun 15, 2018 9:33 pm
Location: Dartford

Re: DB18 Fuel Pump

Post by Dartford Dave »

Hi Tony
As you state the parts book shows the pump to be a type T, but I recently bought a type U from Graham Emmett and the two pumps are identical apart from the valves. The T type has small discs of a sort of impregnated fibre board with a small compression spring and the type U has sealed valve assemblies.

Since fitting the type U I no longer have fuel vapourisation problems. As Graham said it looks like the type U was an improved design on the type T and the overhaul kits from David Beales, John Nash or Derek Sleigh are for the type U (diaphragm the same but comes with new valves).

Many thanks Graham for the pump, the car runs a treat now and no dying when the engine gets hot.

From my experience Tony it's worth changing to the type U.

Dave

qantasqf1
Posts: 299
Joined: Mon Mar 07, 2016 10:13 pm

Re: DB18 Fuel Pump

Post by qantasqf1 »

Well, if you want to maintain ‘Daimler purity’ you should fit the type T, although service parts could be difficult to procure. The valves of the T type pump are made up of individual parts, namely two valve discs (made of micata), two return springs, a brass retainer, a gasket and three countersink screws and a brass housing shrunk into the housing. In fact this is a better arrangement, but discontinued no doubt because of the cost. Externally it is different from the U type in that the top cover is a different shape. I have to say I cannot understand how the U type pump reduces the probability of vaporisation since the pump merely delivers petrol to the carburettor on demand whatever type of pump (mechanical or electric) is fitted. This is an illustration of the T type pump’s top cover.
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Db n j
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Re: DB18 Fuel Pump

Post by Db n j »

Can anyone confirm if the Type-T valves are still available, or will Type-U fit ?

My question relates to our Special Sports, which arrived with a T-type fitted, which will at some point need a refurb.

Thanks

grahamemmett
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Re: DB18 Fuel Pump

Post by grahamemmett »

From David Beales eBay shop:
Daimler DB18 Special Sports & Empress 2.5 Litre Fuel Pump Kit £24
This fuel pump kit includes all gaskets and seals, and also includes the diaphragm and the circular 1 piece valves for the AC U-type and T-type fuel pumps as fitted to the Daimler DB18 Special Sports & 2.5 Litre Empress.
Graham Emmett ¦ DLOC Chairman ¦ chair@dloc.co.uk ¦ 07967 109160
Northwich, Cheshire
DB18 1949 LCV522 (Yes that one with the P100s)

qantasqf1
Posts: 299
Joined: Mon Mar 07, 2016 10:13 pm

Re: DB18 Fuel pump

Post by qantasqf1 »

Although the type T valves and the type U valves aren’t interchangeable, the diaphragm, diaphragm spring and the top cover’s seals are so if David Beales can supply overhaul kits for either of them then you’re laughing. If he can’t supply the type T valves then there’s no reason why you can’t clean up the originals and refit them because as a rule the valves plates are very reliable and give little trouble...their springs are also pretty reliable. However, you may need to make a gasket for the valves’ brass retaining plate (although even these can be reused if handled carefully). I hope I’m not telling grandma to suck eggs, here, but the essential thing to remember is that these valves are delicate little snowflakes and cleanliness is all-important.
Steve.

Dartford Dave
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Joined: Fri Jun 15, 2018 9:33 pm
Location: Dartford

Re: DB18 Fuel Pump

Post by Dartford Dave »

The valves that come with the service kits only fit the U type unfortunately. As has been said previously the type T are individual components and in theory can be serviced without being replaced. My experience has been that in the 4 years I have had the car back on the road I have suffered from vapourisation problems even though I have stripped and cleaned the pump at least 3 times, re-routed the fuel pipe clear of the engine, insulated the fuel pipe, made a heat shield cover the inlet / exhaust manifold. Changed the pump to a U type and all the problems have gone !

I believe that maybe after 70 years and umpteen thousands of cycles of the valves the springs had weakened. I did try changing them for springs I had in a spring kit which although looked the same I had no way of measuring the strength of the springs. At !east the U type valves can be changed easily as they come with the diaphragm.

Whatever the reason why changing the pump resolved my problem, I am now a happy motorist that doesn't have to dread the dying engine at traffic lights then 5 minutes of stress holding up the traffic trying to get it started again.!

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