L20b w/ stock carb - cold start issues - electric choke problem?

[carterb]

We bought a 1978 620KC at the end of summer with a completely stock L20b set-up.  In the summer it started right up but took a while to warm up enough to actually drive.  Now that it is colder, it is a pain to even start, let alone warm up.  Once it is up and going it runs awesome.  I assume this is a choke issue because L-motors do not do well in cold weather with no choke. 

I have never had a carb w/ electric choke so I'm unsue of how to go about trouble shooting it.

Can I look down the carb and see if it is choked or not?

Is the choke on until actuated off or off except when actuated on?

What turns the choke on or off?

I assume a solenoid on the carb actuates a physical link?  Worse case, can the solenoid be removed and coverted to a manual choke lever?  (I'd prefer to get the electric choke working)

Thanks in advance for your comments.

--carter

 

[datzenmike]

Take air filter top off. The choke is partly on because it is cold and the throttle prevents it closing. Step on gas and release and the choke plate should snap full closed and the fast idle cam engaged. You are ready to crank start. Once it starts it should rev 1,800-2,200 to warm it up. Withing 7-8 min the choke should slowly and fully open.
 
Choke fully open

 
Choke fully closed

Electric choke heater

 
Fast idle cam

[carterb]

Choke fully open

 

Choke fully closed

 

Is this like one of those puzzles in the Highlights magazine where you have to try to tell the difference between two photos?  I thought I was pretty good at those but I don't see anything here...

--carter

[KlassicMotion]

 

Is the choke on until actuated off or off except when actuated on?

What turns the choke on or off?

I assume a solenoid on the carb actuates a physical link?  Worse case, can the solenoid be removed and coverted to a manual choke lever?  (I'd prefer to get the electric choke working)

The electric choke is activated by a keyed hot wire.  The current flows through a metallic spring element.  With the key off, the cold metallic spring element  turns the choke valve (butterfly) closed.  When the key is turned on, current flowing through the metallic element heats it up, causing the spring to expand, thus causing the choke valve to open.  As long a current is flowing through the metallic element, keeping it hot, it stays open.  To set the choke (make sure the engine is cold with key off), As Mike said, make sure you "blip" the throttle to release the linkage, and that should close the choke valve. If it doesn't, loosen the three screws holding the black plastic housing on (Mike's third pic), turn the black housing clockwise (typically) to close the valve. Tighten the screws back up and that should do it....

[datzenmike]

Is this like one of those puzzles in the Highlights magazine where you have to try to tell the difference between two photos? I thought I was pretty good at those but I don't see anything here...

--carter

 

Sorry for that I was in a hurry to post and get too bed at same time. Corrected

[carterb]

Thanks guys.  I had no idea there was a procedure to set the choke.  Can't wait to give it a shot.

[datzenmike]

So does it look closed when cold or not?

 

If hard to start the choke is either set way to lean or the linkage is off inside the heater

[carterb]

I tried this morning befor going to work.  I pulled off the air cleaner lid, look down the carb throat and see that the choke is open.  I push the gas pedal all the way down, look back down the carb, and the choke is still open.

I will pull the air cleaner off in the next few days and check the linkage to see what is(n't) happening.

--carter

[KlassicMotion]

I tried this morning befor going to work.  I pulled off the air cleaner lid, look down the carb throat and see that the choke is open.  I push the gas pedal all the way down, look back down the carb, and the choke is still open.

I will pull the air cleaner off in the next few days and check the linkage to see what is(n't) happening.

--carter

 

First off, do you have power to the choke?  Second, if the linkage looks like it's working and you turn the choke housing towards the "rich" side (typically clockwise) and nothin happens, then like Mike said, sometimes the spring element inside the housing will come detached.

[carterb]

So Victoria and I went out last night to see what's up...

 

Here is the choke at rest:

 

This position doesn't change at all as the throttle is swept through it's full motion.

You can grab the choke linkage directly and move the choke about 10 degrees maybe?

 

 

I am failing to see any physical link between the throttle linkage and the choke linkage so I'm unclear how flooring the throttle before start can "set" the choke.

 

Here is a side shot with the gas pedal at rest

 

 

And here it is with the gas pedal fully depressed

 

 

The choke doesn't wiggle a bit during this motion.  My set-up looks a little different than the one Mike posted above too. 

I did not mess with the "choke heater" at all, nor have i checked to see if it is getting +12v.  I will do that next, but wanted to at least get this out there.

What connects the throttle to the choke?  Why can I only rotate the choke manually about 10 degrees?  What/how do you adjust the choke heater?  The arrows imply that the whole thing rotates but where do you loosen it to do so?  Are the screws around the perimeter just a clamp?  So you would loosen that, rotate the plastic housing, and then tighten the clamp back up?

 

Here are some more linkage photos...

 

 

 

Hard to really see what's going on with my eyeballs, let-alone my camera.

[KlassicMotion]

The spring action of the choke valve closing is from the metallic element inside the black housing. I'm guessing your choke just needs to be set (turn the black housing... clockwise, I believe).

 

I'm not sure if this video shows you enough. I can do another clip if you need.

 

http://www.youtube.com/watch?v=VcCWTwESKD8&feature=youtu.be

[datzenmike]

In this picture your index finger is on a linkage that goes down to the fast idle cam. If the throttle is closed the choke plate can't close. Hold the throttle part open and you should be able to move that part with your finger and close the choke plate.

 

 

Spray everything below the black choke heater with carb cleaner or WD-40 and move all linkages through their full range of motion. Probably sticky is all.

 

 

 

Bottom picture...

One other thing to check if this fails is if the choke heater spring is actually connected to the choke shaft. See that J shaped curl on the outside of the coil? It has to be looped around the lever on the choke shaft. Very possible someone took this off and failed to check this as they put it back on. When cold, the spring contracts, or coils tighter, and this tries to turn the choke shaft and close the choke plate. When you step on the gas pedal the linkage is released and the coil will turn the choke shaft closing the choke plate.

 

See the white ceramic thing with the heating coil inside? This is the heater and is designed to take about 8 min or so to warm the choke coil spring. As it warms the coil lengthens and unwinds slowly opening the choke plate.

 

 

 

 

Thanks again Rory for letting me photograph your stash of parts at Canby. I knew this would come in handy

[carterb]

Thanks guys.

I'll look into it more this weekend.

--carter

[banzai510(hainz)]

WTF!!!!Carter you should know this already!!!!!!!!!!!!!

 

Be honest I just turn the choke back where its alwasy open and just pump the gas before start up.

 

My 521 had a electric and I adjusted it and could never get it right. was on too long or not on long enough.

[carterb]

I know.  Except for a couple webers, every datsun I've owned I've run SU carbs.  All with manual chokes.  So I'm actually covering new ground here!  : ) 

[carterb]

Update - everything works fine. 

 

Two problems:

1) I misunderstood the actuation.  I thought the throttle linkage pushed the choke butterfly closed, but the choke "spring" pulls it closed.  The throttle linkage just allows this to happen.  My spring was wound back all the way so there was no tesion to pull it closed.

2) The choke was not getting 12v.  The wrong wire was connected.  That's probably why somone adjusted the choke all the way open in the first place.

 

I connected the right wire, wound the choke up, and now everything is perfect.  Thanks again for the help/advice.

--carter