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DB18-1 fuel pump

Rolo5
Posts: 16
Joined: Mon Jun 19, 2017 8:30 pm
Location: Oxford, UK

DB18-1 fuel pump

Post by Rolo5 »

HI,
I am starting to reassemble my "Christmas Jigsaw puzzle" 1938 DB18-1 tickford DHC. I am told the engine ran last in 2007 after a full rebuild and seems good. Couldnt get the priming lever on the fuel pump to work, seemed disengaged, so stripped down to see what was happening. Cam lever also doesnt seem to activate when moved. Doesnt seem to be the standard fuel pump. Noticed a small screw under the lever housing which, when unscrewed allows the priming lever and the cam lever to work normally, but leaves the screw loose to vibrate out. Thought it might be some form of metering screw but there seems only 2 positions, working or not!
Any advice please?
sorry, dont seem to be able to load the pictures!
Attachments
fuel pump 1.jpg

qantasqf1
Posts: 152
Joined: Mon Mar 07, 2016 10:13 pm

Re: DB18-1 fuel pump

Post by qantasqf1 »

Well something is amiss. Your pump should be either the early type T or the later type U. In either case the screw is a stop to prevent the cam operated lever from overtravel. If it’s missing there’s nothing to stop the lever’s coil spring from dropping out into the sump on pump removal. (Later pumps discarded this screw; instead a lug is cast in the lower housing to do the same thing.) I don’t wish to impugn your AC pump dismantling and assembling skills (they talk like that these days), but are you sure you’ve reassembled it correctly? An afterthought: is it possible the cam operated lever butts up against the screw when the lever is extended? I don’t know whether it’s possible but maybe you’ve fitted the screw on the wrong side of the lever!!!
Steve

Db n j
Posts: 274
Joined: Sun Mar 13, 2016 8:55 am

Re: DB18-1 fuel pump

Post by Db n j »

Can I ask if the lever wasn’t working in situ ?

If so, was it working when you took it off the car ?

I only ask because I spent ages fiddling with a pump showing same characteristics.

Finally worked out that at a certain point of the engine rotation the lever didn’t operate (this is because the lever operates on a cam on the camshaft, which occasionally stops at the wrong place.)

Cured by pressing the starter solenoid a couple of times to move the cam position.

Rolo5
Posts: 16
Joined: Mon Jun 19, 2017 8:30 pm
Location: Oxford, UK

Re: DB18-1 fuel pump

Post by Rolo5 »

Hi,
thanks for the replies.
As best as I can....
Only picked up the whole pile of parts last month. The engine is fully assembled and back in the car as it came and I was told it had run ok, albeit in 2007. Just going through usual checks before actually trying to fire it up.
The pump was already fitted, with the screw fully in. Priming lever feels "floppy" in any position other than with the screw slackened off and off the internal lug, then you can feel pressure and see the piston inside working.
I removed the top of the pump initially with it still on the engine to see if it had seizes or if there was any movement of the "new" (2007) diaphragm, and couldnt see any, which is why I thought i would remove it from the engine.
Other thn seeing the screw was "restricting" movement and slackening it carefully to see what would happen I havent dismantled the lower half.
Realising this was something I was not familiar with I have not explored any further and wrote this post!

With regards to turning the engine position, I assume with it out of the engine and therefore off any cam position it shouldnt have an effect on the lever.

Bearing in mind I am about 25 years out of my comfort zone with this engineering (first time working on a pre-'50's vehicle) very happy to be told "the obvious"!

Db n j
Posts: 274
Joined: Sun Mar 13, 2016 8:55 am

Re: DB18-1 fuel pump

Post by Db n j »

Hi, should work fine off the car.

Did you confirm it’s either a T or U type ?
( stamped on the main case)

Rolo5
Posts: 16
Joined: Mon Jun 19, 2017 8:30 pm
Location: Oxford, UK

Re: DB18-1 fuel pump

Post by Rolo5 »

seems to be stamped "T" type
Attachments
fuel pump type t.jpg
fuel pump type t 2.jpg

Db n j
Posts: 274
Joined: Sun Mar 13, 2016 8:55 am

Re: DB18-1 fuel pump

Post by Db n j »

I have found a t type pump, which mechanically operates, with lever or primer.
If you want a chat to see what is different to yours send me a mail and or a phone number.

Norfolk Lad
Posts: 609
Joined: Wed Feb 10, 2016 8:23 pm

Re: DB18-1 fuel pump

Post by Norfolk Lad »

Looking at photo is the hand primer stuck does it need freeing off on the pivot, have just tried a pump i have that has been off a engine for for years.
That was not returning but has now i have moved it several times , could be worth a look.

Peter

Rolo5
Posts: 16
Joined: Mon Jun 19, 2017 8:30 pm
Location: Oxford, UK

Re: DB18-1 fuel pump

Post by Rolo5 »

doesnt eem stuck, just not engaging unless the screw is out

Norfolk Lad
Posts: 609
Joined: Wed Feb 10, 2016 8:23 pm

Re: DB18-1 fuel pump

Post by Norfolk Lad »

Can you move the lever down so fully open then tighten the screw will it work then , just seem's strange or is it the screw is the wrong one like should it be shorter.

The spring at the pivot point on the priming lever should open the lever well in my case it does.

Have looked at your photo's again think now the lever is the reverse to mine and the spring brings the lever up to the underside of the pump body, then you push it down to prime mine being the reverse of that pulling it up to prime.
Last edited by Norfolk Lad on Sun Feb 09, 2020 6:09 pm, edited 3 times in total.

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