Weber DCOE won't start from cold.

[MightyJoe]

I've got a  single weber DCOE 40 on a 1500cc pre crosslfow. it won't start from cold. like, not at all. to get it running i have to stick on the jump leads and crank it for 45 seconds to a minute, choke on full, pumping the throttle and it'll splutter to life about 50% of the time. the other 50% it'll flood the plugs and when i swap them out for a dry set it'll start with a few cranks but there is fuel leaking from the top of the carb, from the jet cover.  

I've checked everything i can think of, and tried various adjustments of the air mixture screws. starting from 1/2 a turn out all the way to 4 turns out ( i realise this is far too much but just kept on trying)

 

it has a new dizzy cap and rotor, leads, plugs, i've double checked and treble checked the timing and firing order (1,2,4,3 on these weird engines) it's running the stock lift pump, with a malpassi filter king regulator (with a setup gauge) The carb is a dcoe 40 on a spear (lynx style) manifold. 34mm chokes, 165 main jets, 55 F8 idle jets (but have tried with 45 F8, still nothing) 45 pump jets. 

 

When it runs, it's alright. a bit rich but that's down to fine tuning. but i can't even get it to the rough running stage. and once it's started it'll restart without any gas or choke, just straight into life.  its got me beat and i'm well pissed off with it. Any help hugely appreciated. 

 

Joe. 

[downtrail]

Not played with carbs much but float shut off thing not shutting off. fulling the carb with petroleum distillate? 

[tim13]

is it getting a decent squirt of fuel (looking through carb) when you pump the accellerator ? have had a few issues with that on carbs that have been unused for a while . maybe worth checking for vacuum leaks too , they can give odd symptoms . any history on what has been worked on recently ? or how long it has been sitting ? webbers/dellortos usually start ok with 2-3 pumps and no choke

[kicker]

I assume the carb has just been put on the engine, did it come off something similar?

This page has some useful info   http://www.dvandrews.co.uk/

 

From my limited knowledge and experience the main jet seems pretty big

What psi is your fuel running at? Should be somewhere around 3psi.

Where's your float level at? There's a few different ways of setting it, I set mine by measuring the fuel level in the main jet hole (with the jet out) whilst the engine is running, apparently it should be 25mm below the top of the main jet well. It's a bit of a pain as you have keep tweaking the float then screwing the lid back on (with gasket in place) to measure until it reads right.

People seem to recommend starting at 1 turn out for the air mixture.

 

Aaaah DCOE carbs, fun

 

 

 

[kicker]

webbers/dellortos usually start ok with 2-3 pumps and no choke

 

Definitely, haven't even hooked up the choke on mine, prime for 10 secs, 2 pumps on the gas and it purrs into life even on a winter morning in Hanmer Springs

[azzurro]

yep, my dellortos are (now) ace

 

gas definitly shoudnt come out the top - float level is way out (not shutting needle valve), needle valve is worn not shutting off the gas, or fuel pressure too high (no more than 2-3psi like kicker said - for carbs you need flow not pressure).

 

You can set the float with a drill bit of the right diameter betwen the float and the cover with gasket on just closing the needle - there are pletly of diagams online - its about 7mm for dellortos, but find a reliable site and look up your float (they are differnt weights = different cleances)

[MightyJoe]

the carbs came off another 1500 pre crossflow track car with a ported head and pretty fresh bottom end but he was running 2 together. I have the other carb too but  was going to run 1 as i thought it'd be easier to tune! ha. Thats also why i increased the idle jet size as per what i'd read. fuel pressure is set at 1.5psi.  i haven't touched the floats, thats where i'll start tomorrow. Cheers. i'll report back. 

[Rookie]

Start with the basics dude,

 

Does the inlet manifold have any vacuum leaks?
Set the float hight as per the book.

Check that the needle valve is sealing.

Set the pressure on you reg.

Put 1.5 turns out on the idle screws (good place to start but might be off)

Make sure that the cold start curcuit isn't permenently engaged.

Make sure the pump jets are working as they should.

 

Do that and report back. I think if all that is in order your car should work...hopefully haha

[Unclejake]

A single 40 is a great choice for a street 120E motor IMO. Well played.

 

If your spark is good I think your very first checks should be float setting and needle valve.

 

I've run  a single 40, single 45, twin 40s, twin 42s and finally twin 45s on the 1500 pre-crossflow motor - and they always started quickly and well when the float levels and balance were set-up right

 

 

 

P.S. 1-2-4-3 is correct, but don't forget that the distributor runs counter clockwise (like a Honda)

[MightyJoe]

It runs! I got a Haynes "Weber carburetors"  book from the library and it says 8.5mm closed 15mm open for the  floats. They were way off that. i've guestimated the gap cos i don't have a set of drill bits at home. but it starts first time now, no throttle. Cheers for the suggestions. i'll get it to the workshop at the weekend and play with it there where the boss has more tools. 

 

Now i have some tuning to do with it. Cylinders 1 and 2 are dry fouled, and 3 and 4 wet. which is really odd as the way the manifold splits the carb is 1 and 4 off the rear barrel, 2 and 3 off the front one. All good though at least i can get to tuning it now. needs a good run to warm up and then i can see what its doing. They could just be fouled from when it wouldn't start before. 

 

Cheers for all the help and suggestions. Joe.