Sisson Choke

[woodie49]

Is it possible to rebuild a sisson choke? Mine quickly fries the lead from the starter on cranking, so I use a manual choke, but I would like to have this work properly. The ones I see on ebay are a small fortune. I used to see 'em for $35 all the time.

[desoto1939]

Woodie.

Where the wire screws into the top of the choke there should be a piece of plastic or some type of material so that the circuit does not ground or short out the unit.

when the unit is off the car there is a cotter pin that can rbe removed to clean the themostatic metal base plate but do not bend the plate.

I do have the sission choke manual that was used by the dealers and I have scanned this manual to cd.

Yes the prices on these have gone throught the roof and they are getting harder to find at the swap meets even at Hershey.

PM me if you would like a copy.

Rich Hartung

Desoto1939@aol.com

[Joe Flanagan]

I had this happen with two Sisson chokes in a row. The wire would just start burning up as soon as you started cranking the engine. I noticed that on my latest replacement, there is insulation between the screw terminal and the body of the choke itself. I know that insulation was missing on at least one of the chokes that burned up and I'm pretty sure the other didn't have it either, so I assume that was the problem.

I looked into rebuilding mine. They can only be disassembled so far. Then you have to deal with rivets (drill them out, etc.). Even if you could get to the electromagnet inside, I don't think there is much you could do, since it's likely burned up.

[desoto1939]

Woodie,

There are two different sisson chokes. They are ones that fit the 49 plymouth that mount in front on the carb when looking from the fron on the engine and then there are the ones that mount behind the carb so that when you are looking at the carb from the fron of the car the choke is behind the carb.

Which type of mout do you have.? I have a good used Sisson choke that mounts behind the carb and I have bench tested the unit.

It is missing the small arm to move the butterfly but you can take this off of your old unit.

Really there are three models that were used but the more widely found units are the two that I have described above. The other model was used onthe straight eights and some early Mopars.

Rich Hartung

Desoto1939@aol.com

[garbagestate 44]

I seem to recall reading somewhere about a guy who rewound the coil on his sisson but I can't remember where I read it. I guess that if you knew what gauge of laquer coated wire and how many turns etc. you could do it but without a coil winder it would take a while.

[James_Douglas]

Is it possible to rebuild a sisson choke? Mine quickly fries the lead from the starter on cranking, so I use a manual choke, but I would like to have this work properly. The ones I see on ebay are a small fortune. I used to see 'em for $35 all the time.

The unit has a VERY short screw to attach the wire. Over the years people put longer ones in and it causes a short. You MUST make sure that the screw does not go in too deep.

As an aside...I grew up with the grandson of Mr. Sisson.

James

[Don Coatney]

As an aside...I grew up with the grandson of Mr. Sisson.

James

James;

Before I could make such a statement I must grow up first:D Have you done so;)

[woodie49]

It did look like the terminal lacked insulation on one side, so I insulated it and tested it by hooking it direct and it seemed to work fine, the wire did not heat up after 15 or so seconds, so I installed it.

I found two problems. First the linkage I have is too short to fully close the choke. Can someone measure the length of the linkage between the choke lever on the carb and the sisson?

Second, no problems idling in my garage, but after running on the road for about 5 minutes, I did begin to smell the dreaded smell of insulation frying. The wire to the sisson was completely cool with no sign of damage. The starter felt cool, I could find no issue with any of the harness wires and couldn't trace where the smoke was originating, but there was a small amount of smoke which seemed to come from down low around the firewall, maybe the starter. Nothing under the dash was smoking. I did disconnect the sisson and drove home with no further issue, checked everything and later drove for about an hour with the sisson disconnected with no further problem.

It looks like the inside cap on the sisson is insulated, but I can't get access to it. I had thought the sisson only got current on cranking, but it looks like current must flow to it whenever the motor is running. Is this correct?

I am wondering if the inside insulation is faulty and shorts when the manifold heats up.

[Joe Flanagan]

The measurement of the rod is 5 3/8". I also have a 49. I just looked at the two Sisson chokes that burned up on me and neither had insulation at the terminal. I'm tempted to put some there and test them and see if they're really dead after all.

[Niel Hoback]

There should be 0 voltage at the choke at all times except when cranking. Start the engine, remove the wire at the choke and check for voltage. I cannot imagine how there could be, but, whaddaiknow? If by some chance you get a reading, I would suspect the starter motor of some sort of oddity.

[Joe Flanagan]

As an aside...I grew up with the grandson of Mr. Sisson.

The only thing that could top that would be if someone were to post that they were pals with Mr. Sisson himself.

Anyone?

[Tom Skinner]

Gents,

If one gently pulls the Tabs back and di-assembles the Choke,

Then it is relatively easy to re-insulate it using just about anything.

I used 30wt felt (a scrap) and re-assembled it. It works fine.

These things are about industructable.

Clean it up well with a wire wheel and presto a new Sisson Choke.

I snagged a couple on ebay last year cheap (they still can be had)

for a little as $35 or so - but you have to hunt for them pretty much continuosly.

Tom

PS. I didn't know Mr. Sisson or his Grandson:D

[DonaldSmith]

The starter solenoid that goes with the Stisson choke has 4 posts. (This is on my 47 DeSoto, probably similar for other Mopars.)

The battery cable goes to one big post. This also connects the wires to the ammeter and to the horn relay, to give them power. The other big post goes to the Stisson choke, so it is only powered when the solenoid is engaged.

The choke goes half-on per the cold temperature, and the other half on electrically. Presumably when the engine starts, you don't need the full choke.

The two small posts are for the wire from the starter button and the wire from the the generator "A" teminal. When the engine is not running, the generator provides the ground for the starter button circuit, to engage the solenoid and crank the starter. When the engine is running, the current in the generator counteracts any grounding ability, so you can't grind the starter when the engine is running.

(Hint: if your starter just won't engage at all, try removing the wire from the "A' teminal of the generator and grounding the wire. Just don't push the starter button when the engine is running. It'll make a horrible noise, and onlookers will say, "Grind me a pound," like they used to say when you shifted poorly.)

[DonaldSmith]

There is a hole in the brass shaft of the choke lever on the Stisson choke. Find a pin or nail that fits the hole snugly (Snugly is important) or buy Tool C-723 on-line. Good luck.

There's a slot in the bearing, so that the pin or nail (or special tool) can slide through the hole and into the slot when the shaft lines up where it should be when the choke is fully closed.

The nut on the choke lever can be loosened, so that the lever can rotate on the shaft when the shaft is pinned.

With the air cleaner removed, open the throttle about one third (why, I don't know) and move the choke lever until the hole in the brass shaft lines up with the slot in the bearing. Pin the shaft with the pin, nial or special tool.

Loosen the nut on the choke lever, move the lever until the chole plate is closed tight. and tighten the nut. Remove the pin, nail, or special overpriced e-Pay tool.

Replace the air cleaner befoe you go driving around.

[Joe Flanagan]

Gents,

If one gently pulls the Tabs back and di-assembles the Choke,

Then it is relatively easy to re-insulate it using just about anything.

Tom, did you put the felt just underneath the tab where the screw attaches? What did you have to disassemble to do this?

[Tom Skinner]

Joe,

Its been a couple of years now, but the top half comes off and the tab you speak of must be replaced. Then it works again. One must be careful to just pry back the tabs to remove the top - just enough to do so - or else its difficult to get it back together.

Tom

[desoto1939]

Last year i was able to get the full set of tools that were used to adjust both models of the sisson chokes.

Currently on Ebay the small rod tool is currently liste for around $25. I was an avid bicycle rider and also was a bicycle mechanic. Until I found the proper tool I used a Bicycle spoke to make the adjusting rod or tool. If I rememebr correctly in one of my auto repiar manuals I think they stated that a #4 drill bit is a very good subsitiute for the adjusting tool.

I was also to acquire the Sisson testying stand that were used by the dealership and it still has the original themostat and it works. i have used this to test new and used units.

I am at work but will try to post pictures of the tools. I had posted the pictures a couple of months back.

For anyone that is interested I have an original copy of the sisson choke manual and I have scanned the manual onto CD's

It show thes the various models and tools and the stand and the proper way to adjust the chokes.

If anyone is interested then contact me at Desoto1939@aol.com

Rich Hartung

[meadowbrook]

Can someone explain what is the purpose of the electrical wire on the SISSON choke? My Meadowbrook's wire also fried so I removed it. It still opens and closes the choke properly as the engine warms because it gets warmed by the manifold and the engine runs great cold or hot.

So why the electrical connection? It looks like it would cause the choke to momentarily open as you crank the engine. Is it there to reduce the chance of flooding?

[Niel Hoback]

It powers a solenoid that forces the choke plate fully closed. That way the choke is closed when you are cranking the engine. It releases when you stop cranking and the bi-metallic strip takes over by allowing the choke to open slowly as the engine warms.

If your choke is adjusted properly and the wire is not connected, you are not getting full choke effect.

[woodie49]

I beleive the purpose of the electric wire is to power a magnetic switch in the sisson which causes the lever on the sisson to push the choke to a full-closed position.

Gathering from the above comments, once the engine fires and you release the starter, the voltage to the sisson goes away and the choke returns to whereever it is at rest based on your engine temp, controled by the sisson. As the manifold warms, the spring in the sisson relaxes to further open the butterfly on the choke. I guess if you fire it hot, it would immediately return to full open.

I think that the manual says to start a hot motor at half throttle because then another linkage arm causes the choke to be open, overriding the sisson's mechanical action.

[Niel Hoback]

Woodie, great minds think alike. hahahahah

[woodie49]

Woodie, great minds think alike. hahahahah

Yes, we must have been typing at the same time!

[woodie49]

Gents,

If one gently pulls the Tabs back and di-assembles the Choke,

Then it is relatively easy to re-insulate it using just about anything.

I used 30wt felt (a scrap) and re-assembled it. It works fine.

These things are about industructable.

Clean it up well with a wire wheel and presto a new Sisson Choke.

I snagged a couple on ebay last year cheap (they still can be had)

for a little as $35 or so - but you have to hunt for them pretty much continuosly.

Tom

PS. I didn't know Mr. Sisson or his Grandson:D

Tom,

I assume the tabs your are referring to are under the cap (see picture). The insulation is a fairly heavy and stiff material - almost like a circuit board material. Did you replace this or add insulation below it?

Also, anyone familiar with the wiring of a P18 (I have a '49 Woodie) - Assuming that a short occurred after starting (so the sisson wire is no longer live) you would be coonecting positive ground to the terminal on the starter, and back to the solenoid. Would any of this have any effect? Is there a "live wire" in the group that could be completing a circuit? I seemed to have no problem while starting the car, but after several minutes, I could smell insulation burning and a small amount of smoke was coming from what I think was the starter area. After disconnecting the wire from the sisson and isolating it, I had no further problem. But, if the starter only gets power on cranking, I am not sure that there is a circuit to close by making a positive jump to the terminal when the car is on but not cranking.

Sorry if this is a stupid question - I just am no good at electrical and trying to reason my way around it. I may be reaching the wrong conclusion.

[Tom Skinner]

Yes these are the tabs there are 3.

The insulating material is stiff, I chose 30wt felt paper but anything will do.

I believe the choke gets juice at the beginning of the starting cycle - then the temperature relaxes the spring through the asbestos gasket from the manifold which slows down the idle from there. This is not rocket science here.

Relax take a deep breath and adjust your choke (cold) as the service manual directs you to. Prestodigitorium (as Merlin the Magician would say). It works!

Tom

[Tom Skinner]

Also one can test their repair with a 9 volt battery. Hook it up and it should snap shut. Remember to hook it up to a ground also on this test.

Then unhook it because your not supplying heat to it afterwards.

You don't need a fancy tester here its not rocket science.