Auto choke woes

This section is for 1976 to 1987 Chrysler/Mitsubishi/Colt Galant/Sigma/Lonsdale.
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Speedy88
Posts: 107
Joined: Fri Dec 28, 2012 1:35 am
Location: Bristol

Auto choke woes

Post by Speedy88 »

It's winter at the moment so the Sigma doesn't come out much. In these low temperatures the autochoke still doesn't engage (doesn't matter so much in summer). The weird thing is, it will start and idle around 1000rpm absolutely fine. So does this mean that the autochoke is actually working? Just not enough?

Until it is warm, it will just bog down on any more than 1/8th throttle. It also misfires which suggests under-fueling. The choke itself visually never seems to sit anywhere other than vertically, so I don't think it's working. I think it'll be the spring type choke as it's a 77. I'm not entirely sure where to start other than replacing the whole carb? Any help would be appreciated.
zabatron
Posts: 108
Joined: Wed Apr 01, 2009 1:25 am

Re: Auto choke woes

Post by zabatron »

First,try resetting automatic choke by depressing accelerator pedal to floor and releasing before starting engine.If this does not fix your problem,then you need to determine whether you have the early bi-metallic spring type choke or the later wax pellet type choke as both have different problems and fixes.If you can post a picture of the carby here i will be able to tell you which choke you have.
Speedy88
Posts: 107
Joined: Fri Dec 28, 2012 1:35 am
Location: Bristol

Re: Auto choke woes

Post by Speedy88 »

Hi,
Sorry for the delay, here is my carb:

Image
zabatron
Posts: 108
Joined: Wed Apr 01, 2009 1:25 am

Re: Auto choke woes

Post by zabatron »

Definitely the early bi-metallic spring type auto choke.The auto choke assembly is the round bit at rear of the carburettor with the 2 water connections on it. Auto choke operation is controlled by the temperature of the engine coolant..If the choke flap is fully open(vertical) when engine is cold,auto choke is clearly not working and engine will run too lean when cold.First check that the 2 external springs are not broken/binding.Next remove the 2 water hoses and make sure that the water passages on the bi-metal spring assembly are not blocked/rusted out.If auto choke assembly is rusted/blocked internally,you may need pull it apart and clean it out .To adjust ,you must line up the punch mark on the choke housing with the centre graduation/line(you will see 5 lines on the external housing,punch mark must be lined up to centre line.To adjust,loosen the case plate retaining screws,and rotate the choke case as required.).
Most common problem I have seen with this type of choke is where the internals of the choke system corrode and sieze it up.
Speedy88
Posts: 107
Joined: Fri Dec 28, 2012 1:35 am
Location: Bristol

Re: Auto choke woes

Post by Speedy88 »

Ahh! Excellent, I'll investigate this. It makes sense that it would be seized as it does work sometimes. However, even when it does it's quick to disengage the moment you get on the road.
Dan
Posts: 1
Joined: Wed Jun 17, 2015 7:39 am

Re: Auto choke woes

Post by Dan »

Hi Speedy,

How's your car running now, choke sorted? I'm from the UK and I've just got myself the same model and have been reading through your posts. I can't pm yet, do you mind me asking what wheel offset/tyre size your running with the mags. Did you use king lowering springs or cut the standards.

Thanks
Dan
Speedy88
Posts: 107
Joined: Fri Dec 28, 2012 1:35 am
Location: Bristol

Re: Auto choke woes

Post by Speedy88 »

Hi Dan,
Sorry, I've only just seen this. What colour is yours?

Not sorted a choke yet and come back here to investigate carb options as mine has started leaking. Probably try and pick up a cheap Weber or Solex.

I don't know what my offset it to be honest, I'll need to measure. I'm running 20mm spacers on the back because it looks more flush. Just cut springs, about 1.5 coils on the front and the rears are standard. It rides fine but I would like to go coilovers at some point, when I've got the money.
zabatron
Posts: 108
Joined: Wed Apr 01, 2009 1:25 am

Re: Auto choke woes

Post by zabatron »

Carburetor on your car is actually a Solex design which was made under license by Mikuni Corporation in Japan.Very early models actually have Solex written on the top cover,while later versions have "Mikuni Corp,Japan" on them.Rebuild kits and parts are still readily available here in Australia(with the exception of the BI-metal spring auto choke assembly which is no longer available),and are interchangeable between the European(usually French made) Solex versions and the Japanese made Mikuni versions.
As for Weber carburettors,these will give an improvement in both power and fuel economy over the original Solex/Mikuni,and are really easy to fit with an adaptor plate,modified accelerator cable and deletion/looping of choke water hoses.Weber conversions on Sigmas are common here in Australia,and one Sigma model(Peter Wherret Special)actually had a Webber carburettor fitted from the factory.
Post a picture of your carburettor leak,and I might be able to tell you what it is leaking from and how to fix it.
Also,I just remembered that I actually still have a complete Mikuni carburettor(wax pellet choke type) here in my garage even though my Sigma is long gone.I will have to dig it out one day!
zabatron
Posts: 108
Joined: Wed Apr 01, 2009 1:25 am

Re: Auto choke woes

Post by zabatron »

Just a correction to the above post.Peter Wherett Sigma did not not come from factory with Weber carburettor.They used the same mikuni /solex carburettor as other Sigmas,but had factory fitted extractors.This was just pointed out to me by my friend who owned one of these cars back in the 1980s.
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