webers cold start struggle

[checkrail]

Hi, Struggled to start the +2 after two weeks in the garage, I gave five pumps on the pedal and it fired 1st time but however you try to feather the throttle it dies, eventually it picked up fine.
This happens every time if it's not started for 2/3 days, I've tried 2 pumps up to 5 pumps but no difference, it always fires 1st time and once I get it running you cannot fault it.
It's on a mechanical pump and no choke cable

Any ideas will be very welcome Thanks John

[ericbushby]

Hi John,
Firstly it could be other things, but with Webers the fuel evaporates from the float chamber if left standing. You should be able to smell it in the garage.
If you remove the jet cover and one of the large jet stacks you can normally see the fuel surface with a small torch.
If you check this after standing for a few days and then after running you may see a large difference.
If this is the case, then you can prove it is the problem by topping up the fuel chamber to the normal running level from the top. Use a thin dipstick like a cocktail stick to measure the fuel level. The fuel shivers when the stick touches the surface and you will see this with the torch.
If it then starts easily, you will have found the cause.
The large jet stack can be left out for this test as it is not used for starting.
Looking ahead there are several ways that you can prime the carburettors before attempting a start.
Hope this helps.
Eric in Burnley
1967 S3SE DHC

[checkrail]

Thank you Eric I will try your suggestions, but I can't say offhand that I have noticed a petrol smell.

John

[Concrete-crusher]

I would suspect low fuel in the carbs. I have an electric fuel pump and it fires first time and if I then apply the cold start with it running it idles nicely for a couple of minutes until the mix is too rich then with the cold start pushed back all is OK.

The fuel pump was one of the cheap Facit types from Amazon but seems yo work well. I do have a pressure regulator in line and set to minimum.

Steve

[alanr]

You asked this question last November and the answer is the same!
Reconnecting the Choke cable and use until it runs smoothly will solve your problem.
viewtopic.php?f=40&t=48174

Alan.

[MrBonus]

Try 8 pumps. Or the choke. Or 8 pumps and the choke. Or try adding a priming pump or an electric fuel pump. Or any combination of the three because you aren't getting enough fuel at start-up most likely.

[LaikaTheDog]

2 pumps, feather with choke until warm

Or

Full choke, no pumps

Depends on the car !

[richardcox_lotus]

Try 8 pumps. Or the choke. Or 8 pumps and the choke. Or try adding a priming pump or an electric fuel pump. Or any combination of the three because you aren't getting enough fuel at start-up most likely.

As I understand it, multiple pumps or choke use are just to get the fuel from the carb bowls to the throats. Assuming you have a mechanical fuel pump it’s the cranking that will fill the bowls in the first place. So as per earlier comments, you need to identify if your fuel bowls are low/ empty before you try and pump the throttle.

My Weber Sprint does the same.

It’s no big deal really. One you realise how long to crank to fill the bowls, you can then work out how many throttle pumps work best for you.

If you want to reduce wear on the starter motor/ battery from excessive cranking, then install a manual bulb type pump for priming, or switch to an electric pump, or use the car a lot more often

Regards
Richard

[checkrail]

Thanks for all the replies, but as I have already stated I do not have a choke cable.
How come it always fires 1st turn of the key, there must be some fuel left there to do that?

The carbs have the standard airbox and trunking John.

[elans3]

Yes, you'd have to leave the car a long time before ALL the fuel evaporated. My experience is that my Elan is ok to start if left 2 or 3 days in the Summer.(a few days longer in the Winter when ambient temperature is lower).. Any longer than that, and you have to churn over, to get the mech fuel pump to fill the float chambers.
After a few days, the fuel level will drop significantly via evaporation, and the reason yours will fire first time and then die, is that the lower fuel level is enough to provide the accelerator pump mechanism with fuel to feed the pump jets, as the accelerator pump mechanism draws fuel from the bottom of the float chamber via the "back bleed" jet.
That squirt of fuel into the inlet manifold is enough to make the engine fire, but then the lack of fuel height in the float chambers means there's not enough fuel to keep it going.
Every time you pump the throttle on a DCOE, it compounds the starting problem by lowering the float chamber level even more, so you need to churn the starter more to fill the chambers.
It's an issue with all older cars with 40 DCOE's, fed by a mechanical fuel pump, and the answer is one of those remedies stated above, ie fit an electric fuel pump (pressure governed by a Malpassi regulator or the like, and remove the mech pump and blank off the mounting holes in the block), or fit an electric pump (keeping the mech pump), with a switch on or under the dash just to fill the float chambers before attempting to start it, or fit a hand bulb pump to fill them, alongside the mech pump. On my Alfa, and previous Elan's & Alfa's, I've always fitted an electric pump with a pressure regulator between that and the carbs to cure the issue.
My Elan has an almost new mech fuel pump, and what you're experiencing still happens if I leave mine more than 3/4 days. I haven't got round to fitting an electric pump yet, but I will do so before the warm weather comes.

[sprintsoft]

Hi checkrail,

that sounds like normal weber behaviour given that its winter and close to zero degrees at night in the UK.

Yes they do quickly fire into life after a few pumps on the throttle but cannot sustain running as the mixture is just too weak for a cold engine.

You have two options:
run the mixture pig rich so it can run when cold (not recommended, but many are setup like this!)
or
re-install the choke cable.

Regards
Iain

[nmauduit]

one thing you may try (if not tried already) is depressing statically the pedal when cranking, but without pumping (that is after the 2 initial pumpings), to avoid over rich mix yet ease the cranking with less vacuum to pump - then as soon as it fires you may release the accelerator pedal to light warming up level.

[checkrail]

Thanks chaps for all the info, I'm considering a hand bulb pump or buying a choke cable.
Interestingly in the Brian Buckland bible 'The choke is never used'

John

[elans3]

Correct. I've been messing with Weber DCOE's for 45+ years and never had a choke cable fitted, not required.
In this case, petrol has to be available for richness, and when the fuel has evaporated it's not available, so any form of "enrichening" the mixture, either by increasing the jet sizes, deploying the choke, or by tweaking the mixture screws, isn't going to work.
The only solution, (provided everything else is working correctly), is to fill the float chambers with fuel by one of the solutions above, then pump the throttle 2 or 3 times to inject neat fuel into the inlet manifold via the pump jets, and you should have enough fuel left in the float chambers for the engine to keep running with a little "tickling" of the throttle.

[RogerFrench]

I don't really have a dog in this fight, but over the years I've had all sorts of cars with carburetters, Zenith, Solex, SU, Stromberg, Keihin, Weber, Dell'Orto, etc.
One thing I've found for each one is that one size doesn't fit all!
Among our cars is a 67 S3 with modifications including 40 DHLA s and electric fuel pump.
Received wisdom is that I don't need a choke cable, I can start like Elans3 above. True, I can.
But, if I pull the choke it starts just as readily, and I don't need to tickle, I push it in as it warms up. Since this avoids my having to pump a puddle of petrol, I'll stick with it.