Fuel system - Carburettor Autochoke

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Fine Tuning The Autochoke

Tips on fine tuning the autochoke/s from Covkid:

What does the autochoke do and why would I need to adjust it?

Autochokes reduce the amount of air entering the carburettor, thereby richening or weakening the mixture according to engine temperature. Their function, essentially, is to stop the engine stalling when driving away from cold. They work using a bimetallic spring which uncoils depending on carb temperature and were designed to do away with a manual choke. As the choke unwinds, the choke flap will pen further, allowing in more air through the carburettor.

They are NOT entirely accurate however as they are a rather simplified affair but they can be adjusted in a similar way to VW Beetles and others in the v-dub clan to more closely match conditions, improving their effect and reducing fuel consumption. You don't want to be messing with it all year - just a general summer or winter setting will be a happy medium. Modern engines are computer managed and make continual adjustments according to both load and temperature whereas the spring choke is a very basic sensor but you can make it work better and allow for wear in the autochoke itself.

Refer to part 28 here: http://wiki.club8090.co.uk/index.php/Fuel_system_-_Pierburg

The choke is held with three screws which can be loosened and the choke turned a little to increase or decrease the choke effect and once right, the screws gently re-tightened.

In fact in much warmer weather you can back the choke right off until it has no effect - saves fuel. Never come across two bi-metallic springs that worked the same anyway and often found an older one worked better than a new one!

Bear in mind that as its a very rough (if not dumb) sensor, it isn't going to be right, all of the time. A summer/winter setting helps match it more closely to ambient and operating temperatures and if its a daily driver you will save considerable fuel doing that. The alternative is a manual one but then people forget to shut them off and theres no gain.

The auto is merely a compromise and one should not assume that it never requires adjustment. You slacken the three screws slightly and adjust accordingly. In use they're supposed to come off within a minute or two but you may find the choke isn't on enough or on too much. Find the sweet spot for summer (ie no choke on a day when it shouldn't need it) and mark it. Do the same when outside temperatures are brassic (on enough to just stop vehicle stalling during initial warm up) and you'll have your own summer/winter settings for your OWN vehicle that work much more efficiently.