hakanson@orstcs.UUCP (01/05/84)
#N:orstcs:3000026:000:1356
orstcs!hakanson Jan 4 21:51:00 1984
I just finished getting the automatic choke mechanism figured out on my
1980 Dodge Colt (I hope people aren't too tired of my talking about my
car, but here goes...). I'll briefly describe the problem I was having,
then if anyone is interested, I'll post the solution later.
I tuned up the thing just before Christmas, but I couldn't get the idle
speed as slow as the specs require. It had been gradually getting faster
and faster, but only recently got obnoxious, when it got to idling at
around 1200 rpm. Turning the Idle Speed Adjusting Screw had no effect,
so I knew something was wrong with the linkage (the screw is not damaged).
Upon close scrutiny, I discovered that the fast-idle cam was in operation,
even though the automatic choke was not (the choke is a very elegant
mechanism, and has always worked well). I couldn't find any adjustment
for the fast-idle, either in my book or on the linkage itself, so I just
let it go until I had more time. Cleaning and lubricating the linkage(s)
didn't help at all, either. If any of you Dodge Colt/Plymouth Champ or
other Mitsubishi owners (the chokes should be the same or similar) are
interested, or are having the same problem, let me know by E-mail to the
address below, and I'll post the solution.
Marion Hakanson CSnet: hakanson@oregon-state
UUCP : {hp-pcd,teklabs}!orstcs!hakansonhakanson@orstcs.UUCP (01/09/84)
#R:orstcs:3000026:orstcs:3000027:000:4618
orstcs!hakanson Jan 7 13:32:00 1984
I'm sorry I didn't post the choke solution earlier, but I didn't have time.
The problem became fairly obvious when I tried pushing (by hand) the throttle
mechanism toward idle. The idle did indeed slow down, and it stayed there
(did not spring back). But normal operation of the throttle return spring
would not force the throttle back to normal idle. Then, by working the
fast idle lever (it is a bell-crank-like thing that operates the choke via
a gear on one end and the fast-idle via a cam on the other end), I could
also get a normal idle speed. That showed me that the throttle return
mechanism was not at fault -- it was somewhere in the choke/fast-idle system.
I first cleaned and lubricated every moving part outside the carburetor
(and practically everything I could see inside, too!), to no effect other
than to have a nice clean carburetor.
Every automatic choke mechanism I've ever seen or heard of has some method
of sensing the engine-temperature, and the Colt/Champ is no exception. In
fact, this installation is more elegant than most I've worked on, in my
opinion. There is a thing called a "thermo-wax element" which is in a little
coolant chamber below the carb. It has a push-rod attached to it which
apparently pushes on the choke/fast-idle lever as it heats up. Thus, when
cold, spring tension holds the choke and fast-idle at maximum. As the engine
starts, a vacuum-diaphragm pulls off the choke slightly (the amount is adjust-
able by bending a little tab), but the fast-idle amount is unaffected by
anything until that thermo-wax element heats up, expands, and pushes against
the spring tension on the choke/fast-idle lever, which also allows more choke
to be pulled off, and slows the fast-idle. Now, this is all sounding fairly
complex, but if you've ever tried to set/adjust an automatic choke, you must
recognize that this is a fairly simple mechanism (if I can understand it,
then it must not be TOO bad -- I just hope I am describing it well enough
for everyone else!).
Anyway, I finally decided that this thermo-wax element wasn't expanding
as much as it used to -- perhaps due to tiredness or age. So I also
figured that Mitsubishi would be smart enough to realize that this would
happen, and provide an adjustment for it, even though no mention or picture
of one could be found in my service manual (a '79 version, and my '80 car
has one or two slight additions that I've found so far...). Therefore,
I stood on my head over the carb, after removing the air cleaner, and lo and
behold, there was a little white-painted (read "factory set") screw that the
thermo-wax element's push-rod pushes against. In order to set the fast-idle
(and hence the choke pull-off rate) correctly, you first have to free that
screw by turning it in & out most of the way, to get rid of the white paint.
Then, start the engine and let it get to operating temperature. Then, either
with the engine running or stopped (stopped is easier), turn that screw in
until you can see the fast-idle lever just barely stop touching the fast-idle
cam on the throttle shaft. Just to be safe, I left a fairly small gap between
the two with the fast-idle at "full-off," approximately 1-2mm.
Now, you should recheck and set the idle-speed and timing, etc., according
to normal tune-up procedures, and then check once more to make sure that
the fast-idle lever is not touching the fast-idle cam when the engine is
at operating temperature. When all is set, you should put a drop of white-out
or white paint (or any color will do, I s'pose) on the threads of that
push-rod screw in order to keep it from moving. After all this is done,
you may have to go back and reset the choke pull-off by bending that little
tab (this procedure is described in the service manual). I try to set my choke
as lean as possible, or the plugs get fouled easily, & the mileage will be
worse than necessary. The Colt runs quite well when cold, which is more than
you can say for a lot of cars, I guess.
Now that the idle speed is normal, I notice that it seems so slow that
I sometimes think the engine has stalled instead of just idling. And
of course, gas mileage is better, and it doesn't "run on" when you shut
it off, anymore. But the biggest annoyance that has disappeared is that
the "deceleration fuel shutoff" doesn't cause a jerk when it disengages.
Things are back to their former smoothness. Needless to say, I'm somewhat
proud of myself. Of course, I can't get into my car until my head shrinks
a little....
Marion Hakanson CSnet: hakanson@oregon-state
UUCP : {hp-pcd,teklabs}!orstcs!hakanson