Lotus Elan

dellortos--- pump jet mystery

PostPost by: phatmendus » Fri Sep 16, 2005 5:44 pm

hi, can somebody help. i have twin dellortos which have been refurbished by the previous owner. the car has been off the road the whole time. I now come to the stage where i am almost finished, but i am having great trouble starting the car from cold. I understand that the pump jet should squirt some fuel into the barrel of the carb to help starting. if this is correct none of the barrels are getting any fuel into them. To get the car to start I have to take of the main jet cover and tip a small amount of petrol in. It then starts first time.

I have just taken the top off the carbs, cleaned all the jets and the float chamber, but this made no difference. can anyone help, or if not just explain what should be happenning in dellortos (is this fuel squirt wrong?) I am thinking that it must be right as everyone suggests jabbing the throttle a few times before starting to pump a bit of fuel in.

oh lastly the fuel is getting into the carbs fine. it is filling the float chambers up etc, and once the car is runnning it goes ok.

Thanks
Simon
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PostPost by: types26/36 » Fri Sep 16, 2005 6:01 pm

The pump jets are under the brass screws on the raised boss on the carb, you do not have to take off the carb top. When you take out the brass headed screw pull out the pump jets, they sometimes stick.With the jets out work the throttle and you should see petrol come up the jet hole this will show the pumps are working, clean out the very small hole in the end of the jet with a thin strand of wire.
Refit the jets noteing they only fit in one position, they have a flat on them.
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PostPost by: phatmendus » Fri Sep 16, 2005 6:19 pm

thanks for the info Brian.I have already done most of that, apart from to check if fuel is coming out where the pump jet hole is. What do i do if petrol is not coming out? where is the actual pump and is it repairable or replaceable?

Simon
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PostPost by: types26/36 » Fri Sep 16, 2005 6:33 pm

Then chances are that the pump diaphrams are defective, they are on the underside of the carb held on with four screws, you would have to take off the carbs and it would be as well to get a kit, clean the carbs making sure all the passageways are open and replace gaskets and seals.
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PostPost by: phatmendus » Fri Sep 16, 2005 7:36 pm

great. thanks for the info Brian.

Simon
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PostPost by: chicagojeff » Sat Sep 17, 2005 2:55 am

Just a friendly note to say that I really appreciate Brian's posts! I am not having trouble with my Delorttos, but I went and looked at them and learned something new after this last post! thanks! Jeff
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PostPost by: phatmendus » Sat Sep 17, 2005 4:49 pm

I have just checked the pump jets as Brian suggested. I took out each jet, then openned and closed the throttle. No fuel was being pumped up, in either carb. However I could just see the fuel level down the aperture where the jet was. Does this mean that both my carbs have faulty pumps do you think, or would there be a more obvious solution?

I really dont want to have to take the carbs apart if there is actually nothing wrong or it is a simple problem to fix.

Any further advice as I would have thought is unlikely for both carbs to be faulty.

Thanks

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PostPost by: Petter Hval » Sat Sep 17, 2005 5:50 pm

According to MILES WILKINS:" Starting cold engine- Dellortos-use full
choke. Do not pump the throttle, for these carburettors do not operate
in the same way as the Webers. {Unforttunately, some modern twin-
cams heve been blown up becaus their owners kept pumping away,
thinking that their Dellortos looked in the same as Webers - this fills the
air box with neat fuel, and if a flash-back occurs there will be an explosion}.
As soon as the engine starts, progressively push in the choke and begin
to use the throtle".

Regards
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PostPost by: types26/36 » Sat Sep 17, 2005 6:12 pm

If you have taken the pump jets out and you have vigorously opened the throttle's a reasonable amount a rise in the petrol in the pump jet hole WILL be evedent! just by loosening the brass screw (pump jet holder) and opererating the throttle rapidly WILL result in a leak from the the brass screw.
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PostPost by: types26/36 » Sat Sep 17, 2005 6:55 pm

As a footnote to the above:
It has been a while since I stripped a Deloto but there IS some means (a ball or a valve--- one way) to prevent the the fuel returning to the pump chamber on the pump stroke otherwise the fuel would not be pumped, from memory I think its a ball in the diaphram cover plate. This ball/valve could be stuck resulting in no fuel being pumped, yet the diaphrams could still be serviceable.
The very name "pump jet" describes exactly what the function of the pump jet is AND it should pump fuel, if it is not pumping fuel it is NOT working for some reason.
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PostPost by: elansprint71 » Sat Sep 17, 2005 7:59 pm

If all is working well there should be a VERY appreciable squirt of fuel, as Brian suggested the diaphragm may not be intact and I would echo his suggestion to get a service kit and replace all the bits supplied in it.
Miles Wilkins is not the font of all knowledge when it comes to Dellortos; yes they do work slightly differently from Webers but they do not need the choke at all. My starting procedure developed over several cars and many years is: Cold- car not used for a couple of days (or more), four full strokes of the accelerator pedal, foot off, turn key, lightly touch pedal as engine is turning- it starts!
Cold, car used earlier that day- turn key, lightly touch pedal as engine is turning- it starts!
Hot/very hot- turn key, it usually starts at the slightest touch of the pedal; if not then foot to floor, turn key and churn, it usually starts after a few seconds, release pedal before engine grenades!

Incidentally, I have found that, despite being a friend of Brian Gush, Brian Goodison's advice on all matters Lotus is spot on!!!

Cheers,
Pete :lol:
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PostPost by: freddy22112211 » Sat Sep 17, 2005 8:09 pm

Just goes to show you that what somebody recently said is true - twin cams vary. My dellorto sprint always needs choke - won't start from cold without it. Gordon
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PostPost by: Petter Hval » Sat Sep 17, 2005 9:13 pm

I have newer heard of Brian Goadison? But I kow that M.W. have been
with T.C. for more than 40 years.
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PostPost by: phatmendus » Sun Sep 18, 2005 4:30 pm

Problem solved, the previous owner had put the springs the wrong side of the diaphram. bit of a pain having to take the carbs off, but anyway.

Thanks for the information

Simon
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PostPost by: elansprint71 » Sun Sep 18, 2005 9:53 pm

Petter,
I have never heard of Brian Goadison either!

Goodison, yes.

Wilkins' Twin-Cam book has more than a few mistakes in it, some of which were corrected in the second printing. Would I advise anyone to go out and buy it? Yes, but as with all things Lotus, sometimes you have to figure it out for yourself. ;-)

Pete.
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