The first car I can remember my parents having (a Vauxhall Cavalier manufactured in 1987) had a manual choke. I remember when they bought their next car, brand new in 1992, they were pleased to find it had no choke, being a fuel injected engine. The recommended procedure for starting the car was to turn the ignition on, and wait 2 seconds for a faint buzzing sound to stop before cranking the starter - this was the fuel pump priming the injectors, I believe. So no need to touch the accelerator pedal for starting.
So based on this, I believe manual chokes remained common in UK vehicles right up to the end of the 1980s, more or less coinciding with the widespread introduction of fuel injected engines.
Automatic chokes sucked. Ford fitted one to the ‘vv’ carb on the mk5 Cortina. They ended up implementing a workshop repair for all the problematic vv carbs which resulted in simply replacing the autochoke for a manual choke (i think it was a mod to the carb, not a complete replacement).
Having worked in the UK auto industry for 20 years, I have come to the conclusion that manufacturers will only change their engine design when dictated to by legislation (emissions, for example).
I suspect the autochoke was another of the vehicle manufacturers attempts at further removal of the driver from the inconvenience of actually driving the machine (not always a bad thing, IMO) but fuel injection was prob too expensive for the price point they were planning to pitch the particular vehicle…
For a fuel-air mixture to burn, you need enough fuel vapor to form a combustible mixture. In a fully warmed up engine, the intake tract and intake valve are nice and warm, so all of the liquid fuel that’s being put into the intake tract (whether by carburetor or fuel injector) evaporates before the spark tries to light the mixture. In a cold engine, only the lighter fractions of the fuel blend evaporate quickly enough to generate fuel vapor in time; to compensate, your fuel system has to supply extra fuel so that there are enough of these lighter fractions evaporating in time to form a combustible mixture.
On a fuel injection system (i.e. any car sold in the US since the mid-1980s), a computer is running the whole show. It has temperature sensors so it knows how warm/cold the engine is, how warm/cold the environment is, and it’s been pre-programmed to deliberately inject extra fuel if conditions warrant.
On a carburetted system, either the operator (via a manual knob on the dashboard) or some clever mechanism (controlled by a temperature-sensitive bimetallic spring) closes a choke plate upstream of the carburetor’s throat, generating a bit of extra vacuum in the throat of the carburetor that makes the engine suck a little extra fuel in. Carburetted cars typically also included an “accelerator pump” that squirted a bit of extra fuel into the intake tract whenever the driver quickly put his foot down on the accelerator pedal; this was to cope with rapid load transients during normal driving (e.g. stomping your foot to the floor when the light turns green), but also served to squirt some extra fuel in just prior to starting the engine (and it also often “set” the choke plate prior to a cold start).
On a fuel-injected engine, an actual physical choke plate wouldn’t do anything. The amount of fuel being injected is entirely up to the computer and whether it’s commanding the injectors to be open or not. If an engine has a fuel injection system with a manual “choke”, it’s probably just a lever that opens the throttle a bit for a fast-idle. BMW’s boxer motorcycle engine of the late 1990s and early 2000s was like this: it was fuel-injected, and there was a lever on the handlebar labeled “CHOKE”, but all it did was tug on the main throttle cable to open the throttles a bit. I’m still not sure why this worked at all. (BMW boxer motorcycle engines have since gone completely automatic, with electronic throttle control and computer-controlled cold-start functionality, same as cars).
Mixture control on an airplane is required so that the plane can operate properly over a wide range of altitudes. At high altitude, ambient pressure is less, so you tweak the mixture control so that less fuel goes in, restoring the proper air/fuel ratio - likewise, when descending to lower altitude, you have to increase fueling to compensate for the denser ambient air. I’m not a pilot, but AIUI this is typically done by monitoring exhaust gas temperature. A lean mixture burns slowly and so for a given engine operating condition (i.e. timing, RPM, and throttle position) results in higher exhaust gas temperature. This is why excessively lean operation, if left unchecked, can fry exhaust valves. Proper mixture control during different phases of flight assures good fuel economy and reliable operation (i.e. no spark plug fouling or burnt exhaust valves). People who tour on carburetted motorcycles have a similar experience: if you ride from, say, Iowa to Utah, you will need to adjust your carburetor along the way to cope with the altitude change.
Street-legal passenger cars do not include mixture control because this would make it impossible to meet EPA tailpipe emissions regulations. With the exception of cold-start enrichment, your car runs right around stoichiometric almost all the time so that the exhaust aftertreatment can best do its thing to convert engine-out pollutants to more harmless stuff.
The main problem was not the choke but the carburetor, especially during start up. After all the choke is only a method to modify the carburetor’s mixture, and carburetors were lousy imprecise devices that could act vastly different among the same model. So the choke make it easier, and possible, to get it started. But it was not as simple as on/off, but you had to learn how your car worked as each carburetor had it’s own ways about it, , what it liked and didn’t to get a good start.
This is where automatic chokes could not compete, it would always be a lousy compromise of what a manual choke could do as it was basically a pre-programed mechanism for something that is temperamental. Add to that auto-chokes did not last. As stated it was a common retrofit to put in a manual choke in place of the auto choke.
So the answer was because carburetors were lousy and inconsistent at startup that a one size fits all solution was not the best one, far better to have human intervention.
As a Millennial I don’t think I’ve ever driven a car that didn’t have fuel injection, but I did listen to Car Talk religiously every Saturday when it was on the air. From what I gathered from Click and Clack, didn’t pumping the gas pedal have something to do with setting the “automatic” choke? Which is to say they weren’t fully automatic back then; you had to pump the gas to engage the choke, then it would automatically release when the engine warmed up. At least that’s my understanding based on listening to the radio.
I can still remember the surge of pure acceleration I got when I pushed the choke in, going up the hill just outside the property:)
Would have been about 1985. That car took seconds to warm up, so I was round the corner before I pushed the choke in. Driving the truck, the choke went in and the pedal backed off as soon as the engine started.
As mentioned above, early automatic chokes were crap, but I think that changed with Electronic Ignition. I don’t remember a choke on my sister’s 1980~something Mazda 626, which was not a ‘base’ car, but was not fuel injection.
Automatic chokes were tricky devices. They were activated with a spring that contracted when cold and were attached to another device called a “fast idle cam” that held the throttle open somewhat after a cold start. when you stepped on the accelerator, it activated the choke spring that snapped a butterfly valve at the top of the carburetor closed to limit the air flow into the carburetor and richen the fuel mixture temporarily. Then, once the engine started a vacuum device would pull the choke valve open a limited amount and as the spring warmed up from engine heat either on the side of the carburetor or on the intake manifold, the spring expanded and opened the choke further. A tap of the accelerator pedal would drop the fast idle down to normal idle and you were ready to drive away. Until this process was complete, cars tended to stumble on acceleration hence it was important to “warm it up” in colder weather.
That was how automatic chokes worked in a perfect world and I assure you, as a mechanic in a former life chokes were a PITA!
My '66 MGB has a manual choke. (So did my first '66 MGB.) The '77 MGBs I had in the '80s had automatic choke. I think of manual choke as an anti-theft device.
My mother’s '79 Mazda RX-7 had a semi-automatic choke. You pulled out the knob befor estarting the car, and you were supposed to push it in when the engine was warm; but f you forgot to push it in, the car did it for you. An odd sort of half-measure.
The last car I remember with a manual choke was a little mid-to-late sixties Datsun one of my uncles had acquired as an inexpensive second car. It also had a manual transmission, which was something I’d never seen before, as all the adults in my life had cars with automatics.
I think that’s also the last car I ever saw with a manual choke.
They stuck around a lot longer on motorcycles. There are still motorcycles manufactured with carburetors, and they will have a choke (actually more likely an enrichener, but it’s still manual). I’ve owned a few.
one of the reasons they didn’t work well is they were locked into a useless setting from the factory to maintain pollution control. They also added vacuum pull-downs and electric heating elements that pulled them open too soon. Basically they got the car started and then you were on your own. Pulling out in front of someone was a dangerous thing in the 70’s. the engine would often stall.
Disconnecting all that crap usually made the engine much more predictable when cold.
