Difficult Cold Starting - Dellortos - 130/5

[alan71]

Tim,
I was interested to hear you use the choke on Dellortos, I have always pumped the throttle a couple of times as I would with Webers. I never understood the warning in Miles Wilkins book not to do this, both carbs seemed to work the same way.
Having just stripped down a set of Dellortos I notice the accelerator pump directs fuel downwards, unlike the Weber which sprays it horizontally towards the inlet. So if you pump the throttle when the engine isn?t running I suppose there is no airflow and you just get a pool of fuel in the barrel of the carb.
Also I just assumed the choke was as hopeless as it is on Webers, when I get it all back together I?ll give it a go.

Alan.

[terryp]

Tim
Too be honest I've not perfected my starting technique but It would definitely involve the choke somehow. (although I'm not sure how)
Let me know when you try. I think Miles Wilkins book is correct

Best Regards

Terry

[tdafforn]

I believe that the Dellorto choke is far superior to that of the webers. Which probably explains why you rarely hear about methods to block it off like you do with the webers.
I am interested that your Dellorto accelerator jets shoot the fuel downwards, mine certainly shoots it horizontally.
I am going to take the +2 for a run on the weekend to begin the runing in process for the new engine. I'll see what a fully open choke does!
Tim
PS my experience so far with twin chokes and cars is that the starting procedure is quite different depending upon the car. sometimes a shift in the timing or new plugs can upset it. My best recipe has been to use the car loads and then it comes naturally

[terryp]

Tim
I think your last point holds the key. I bought "Lola" last July on ebay as "fully restored" having gone through "a full nut and bolt restoration" I think it will be able to be driven in a couple of weeks after about ?1500 in parts and 6 frustrating months.
Thanks for your replys

Terry
PS Before everyone says why did you buy a car from ebay without seeing it (!) I live in France , wanted a plus 2. This was a garage (??!!) on ebay that was prepared at the time to deliver (after the end of the auction they renaged) I thought the delivery / cost of searching would equal the risk of buying in that way. Anyway a lesson learnt and now I have a nice car!

[Robbie693]

I always have to use the choke, full out, when the weather is cold or if I haven't used the car for a few weeks.

When it starts, I have to keep the choke open for half a minute or so because using the throttle will stall it. Gradually pushing the choke in then adding a bit of throttle to keep the revs up. Then its ready to drive.

Having said all that, I do have a suspected failed head gasket (soon to be remedied) which my be a contributary factor to the convoluted starting process. (Try saying that after a few beers!)

[worzel]

Hi to all

Can only tell of my own experiences but I've never used the choke in 30 years of ownership. Two-three stabs of the throttle and just hold it slightly open. If I'm using the car regularly it invariably fires first time. If not used for a few weeks maybe three or four short bursts on the starter. Even stone cold it never appears to want to stall but runs at around 750 revs rising to 950 when hot. I seem to recall road testers regularly pointing out the redundant nature of the choke when the cars were new.

Mine runs on dellortos but even on webers the same procedure worked. As for differences between the carbs- when I bought this car back in 1978 it was equipped with webers but I found these much more difficult to set up and they appeared to go off song fairly quickly. Around 1980 I bought a set of secondhand dellortos that were far easier to set up. Didn't seem to make any difference to performance over the webers though.

In 2003 I bought a brand new pair of the modern dellortos and these are even easier to set up- in fact when I first fitted them I simply balanced the throttles and wound out the slow running screws five full turns and it ran like that for a couple of years without any problems. Later I bought a proper balancing tool and set them up "properly" in 2005 using a colourtune. It seems the threads on the slow running screws on these later carbs are much finer than earlier ones so a full turn out has less effect than before. I seem to recall that on webers you only needed to unscrew these by about three quarters so it seems a pretty crude adjustment by comparison.

As a matter of interest the Excel instructions in the manual merely suggest unscrewing these screws three full turns then connecting a gas tester and then screwing/unscrewing each by a quarter turn at a time until the correct co registers so they cannot be very sensitive.

Regards

John

[alan71]

It?s still in bits at the moment so I can?t check but as you can see the Dellorto seems to direct the fuel downwards. Although there is a flat on one side so it will only fit in one way round, like the Weber.
Also I remember once operating the throttle with the carbs off the car and seeing a jet of fuel spray out, or was that with the Webers. I?m getting confused now.

Alan

[worzel]

Hi

Dellorto do sell conversion jets that pump the fuel horizontally. I think I paid about ?12 for four around 18 years ago.

Regards

John

[terryp]

Hello
What are we saying here that cars with pump jets with the hole at the bottom would be more difficult to start than cars with the hole on the side?????

Terry

[tdafforn]

Makes sense...
Mine must have had the conversion already as I have experienced it squirting fuel over my feet when I removed the carbs to rebuild them!!
Tim

[worzel]

Hi again

Re my earlier comment about horizontal pump jets- I seem to remember that they were an improvement over the vertical type- it's a long time since I did the swap however but as I don't "tinker" just for the sake of it I'm pretty sure I had a sound reason for switching. Since (correct me on this point) later carbs had horizontal jets as std I'm assuming that they were an improvement as the mAchining costs must have been greater.

Regards

John

[handi_andi]

Hiya
Your problem seems to be similar to the one I have been having getting my car started which is also fitted with Dells. My plugs were nice and clean but were getting wetted with fuel and the spark was getting killed. Given you said that after drying and cleaning the plugs it started fine then would that not support the idea. I have just got away from that problem, into a bunch of other ones, by fitting iridium plugs which give such a hot spark first time that the engine fires instantly. Just thought I would share my own experience in case it is any help.
Cheers
Andy

[terryp]

Andy
What type of plugs are they, are they NGK and if so what number. I'll give them a try when I need to change them next.
Also do you know whether your pump jets are the older straight out or newer side outlet type?

Terry

[tdafforn]

I can imagine that with the downward pointing jets if you don't start in the first few attempts the fuel probably pools and then drbbles down the inlet tract into the cylinder, where it splashes around and wets the plugs..
My old engine was a terror for this, but I also put this down to it being a very very tired engine!!
Tim

[handi_andi]

Hiya
Given the comment about downward pointing jets I would have to say I would assume mine are downward pointing but have never taken carbs apart to invesitgate, how would one tell from the outside.

The plugs are Denson Iridium IW20, the book says IW22 but the shop didn't have any in stock and the IW20s are a hotter plug and given previous comments about the twink needing hotter plugs I settled for the. Particularly as they are also fitted to the Subaru Imprezza WRC. I tested them on the cam shaft cover before fitting and was very very impressed by the nice blue purple spark each one gave out. They are not cheap though at around ?40 a set, however, haveing been through two NGK sets at a tenner each figured it was worth it

Andy