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Discussion Starter #1
Our 1985 2.0 liter spider starts ok during the warm months, over 70 degrees, but will not start on it's own in colder weather. SA spray of starting fluid gets her going instantly but no matter how many pumps it will not start. Engine has 40 DCOE Webers with cable operated chokes (that appear to be working). Engine is freshly rebuilt with good compression.

Thanks
 

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Sounds like your accelerator pumps aren’t doing their thing.
Get a mirror and peer down the carb throats as you pump the throttle linkage: see and hear petrol squirting into the throats? Air cleaner top will have to come off to view...but I suspect you know that if you’re spraying starting fluid around.
No good steady fuel stream with each push, nice and even on each throat? To further diagnose, you can remove the screw cover to each jet to see if the fuel is getting to the chamber above the jets, and also lift out the jets themselves (they just pull up and out) to see if the jets are blocked (the outlet hole in each is pretty tiny). If you’re not sure which are the jet covers, they are the biggest brass screws, on the tallest towers, closer to the air cleaner side. Four of them, one for each carb throat. Check their o-rings too. And don’t overtighten.
 

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After using the starting fluid, does the engine continue to run/idle? Does the choke cable have any noticeable effect on the engine running when it's pulled - so check if the cable is connected and the enrichment mechanisms are working. Do you have the hand throttle cable connected - to boost the idle speed when cold. Could the no start be due to lack of use in the winter months - mine is difficult to start when not used for a long period unless the carbs are primed with fuel first - no matter what the ambient temperature is. Are you using an electric or mechanical fuel pump?
 

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Discussion Starter #4
Once she starts, she runs great at a high idle from having the choke cable pulled all the way out. No hand throttle. Electric fuel pump, 2 psi. I am thinking the "fuel enrichment" function of the choke system is not working properly. From what I can tell the choke circuit is a carb within a carb. Even in the summer months she requires several pumps of the gas pedal to get started with the choke level pulled all the way out. When warm, she starts/runs good
 

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Discussion Starter #6
Rubber couplings are new, she runs fine once warmed. Just very difficult starting when cold
 

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So also no off idle stumble? This would rule out the accel pumps imho
What happens if you turn idel screw out to close the butterflies a little bit?
 

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Strange, as my understanding is the "choke" only does fuel enrichment. It doesn't really raise the idle as such, although enriching and a small amount of extra "air charge" from the enrichment system will give a small lift in speed. Mine needs the hand throttle to give a good idle speed after start. I also give it 5 pumps on the throttle and use the choke to start on any ambient start - more so if it's really cold.

Before you do a start, do you leave the ignition on for a period to ensure that the carbs are fully primed (fuel bowls are full) ?
 

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Discussion Starter #11
I understand the choke system within our 40DCOE carbs are for enrichment only and the hand throttle will increase idle speed if required. Actuating the chokes does increase idle speed about 500 or 700 rpms when cold, but not sure why?
Fuel pressure is 2 psi, runs full throttle no problem, does not appear to starve for fuel. I have changed the idle jets several times in search for the correct one. I can pump the gas pedal 20 times, still no start.
 

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If you can run fine at WOT with 2 psi fuel pressure then you most likely have oversized or leaking float valves.
 

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The enrichment starting system bleeds both fuel AND air when activated, so should increase idle speed somewhat. On my car, it’ll lift the idle by 1000 RPMs at times.
 
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