choke breaker jet not working

[Gokhan]

I've had my '83 Tercel since 1984 and the only thing I have had to do with the choke is occasionally spray some WD-40 on the associated linkage if it was hanging up, as evidenced by the choke not closing when the engine was started cold.

A carburetor + choke cleaner like the Gumout spray will work much better because oil will attract dirt and gum and make it stick. I wouldn't recommend oil as a result on any of the carburetor parts. A quality spray like Gumout will keep things clean and frictionfree for years. I've never head any sticking problem. if you keep the oil off, things shouldn't stick. Critical linkage joints have plastic bushings and don't require lubrication.

[Gokhan]

I have now verified that the problem is a fully closed choked. A bad choke-breaker diaphragm A is the likely culprit. Here are the details:

After a fairly cold night, I removed the air-cleaner cover. The choke was at around 55 degrees from the horizontal.

Pressed the accelerator all the way once and it fully closed the choked.

Pressed the accelerator all the way three more times to fully set the fast-idle cam.

I started the engine and the choke remained fully closed for more than a minute. Engine was idling very rough after the first few seconds.

When the coolant temperature rose, probably to around 12 C (54 F), choke-breaker diaphragm B opened the choke to around 55 degrees and the engine started smooth fast idle. The rest of the warm-up was normal and smooth. When I kicked the accelerator, it fully opened the choke (90 degrees) and the idle returned to slow idle.

Since I checked the jet (which was only a couple of years old) and even replaced it with a very brand-new one, I know that the problem is not really the jet. Therefore, the problem seems to be with the choke-breaker diaphragm A. Since there is no easy remedy for the choke breaker, it's a bummer. In fact, I believe the choke breaker is welded to the air horn and cannot be removed. It wouldn't be available as a new part from the dealer and I am not going to replace the air horn with a salvaged one, as I rebuilt my carburetor three years ago.

I can perhaps try putting a straight hose instead of the jet. If there is a small vacuum leak at diaphragm A, this could do the trick. However, I doubt it, as I'm guessing the problem is a dried-up and hardened diaphragm A. Chances are that the filters inside the jet don't filter the gasoline vapors, which harm diaphragm A, and with that end of the choke breaker directly attached to the carburetor, it must be getting really hot and diaphragm A may have hardened over the years as a result.

Meanwhile, I will try starting the engine without fully depressing and releasing the accelerator with a cold engine. This won't set the choke closed and won't set the fast-idle cam but I have to see if the cold engine will start easily and run smoothly with the choke around 55 degrees and the throttle valve at slow idle. I will report on that.

[Rickety Rhino]

Folks,
The problem was the choke breaker A side not holding vacuum. I replaced the choke breaker, and the problem was fixed!
I was misled into thinking it was the jet, because I couldn't blow air through the jet per the FSM test. Later I used a
vacuum tester, and the jet(s) worked fine, delaying the vacuum exactly as expected.
Cheers,
Rickety

[Gokhan]

Folks,
The problem was the choke breaker A side not holding vacuum. I replaced the choke breaker, and the problem was fixed!
I was misled into thinking it was the jet, because I couldn't blow air through the jet per the FSM test. Later I used a
vacuum tester, and the jet(s) worked fine, delaying the vacuum exactly as expected.
Cheers,
Rickety

Where did you get the choke breaker from? Was it easy to replace?

PS: I tried cold-starting below 12 C without pressing and releasing the accelerator but that doesn't work -- the engine stops immediately after it starts. The only way is to cold-start it as usual (by pressing and releasing the pedal) and then when it starts rough idling, to press the accelerator about half way until it warms to about 12 C and the choke-breaker diaphragm B kicks in.

[Gokhan]

Folks,
The problem was the choke breaker A side not holding vacuum. I replaced the choke breaker, and the problem was fixed!
I was misled into thinking it was the jet, because I couldn't blow air through the jet per the FSM test. Later I used a
vacuum tester, and the jet(s) worked fine, delaying the vacuum exactly as expected.
Cheers,
Rickety

Where did you get the choke breaker from? Was it easy to replace?

PS: I tried cold-starting below 12 C without pressing and releasing the accelerator but that doesn't work -- the engine stops immediately after it starts. The only way is to cold-start it as usual (by pressing and releasing the pedal) and then when it starts rough idling, to press the accelerator about half way until it warms to about 12 C and the choke-breaker diaphragm B kicks in.

Well, the choke-breaker is riveted onto the air horn; therefore, it's apparently not meant to be removable and replaceable. Perhaps it's possible to remove the bracket the automatic choke and choke breaker are riveted onto and replace both. Otherwise, you would have to break the rivets and then attach a new one with screws. On top of that, removal of the air horn is rebuilding the upper 1/3 of the carburetor. In addition, you can't get a new air horn or choke breaker from the dealer. I rebuilt my carburetor three years ago and I have no intention of doing this. I will have to live with a choke breaker with a bad diaphragm A.

This link contains a complete set of an assembly and teardown pictures of the carburetor I took when I rebuilt it.

[Petros]

not having the choke breaker working is only a minor inconvenience anyway, it is activated when the choke is fully closed which is only a few min. from a cold start. Earlier auto choke carbs used a mechanical linkage to open the choke when you hit the throttle, I wonder if there is a way to rig up some kind of home made linkage to do this, of course it has to be designed to not interfere with anything else, especially after the choke if fully open.

[Gokhan]

Canadian models have an adjustable and removable automatic-choke coil housing. By removing the automatic-choke coil housing, you can access the mounting screws of the choke-breaker bracket and remove the choke breaker with its bracket. US models have the automatic-choke coil housing riveted and you would have to cut the rivets to open it and remove the choke-breaker with its bracket. This is probably because of US emissions regulations:

[dlb]

Well, the choke-breaker is riveted onto the air horn; therefore, it's apparently not meant to be removable and replaceable. Perhaps it's possible to remove the bracket the automatic choke and choke breaker are riveted onto and replace both. Otherwise, you would have to break the rivets and then attach a new one with screws. On top of that, removal of the air horn is rebuilding the upper 1/3 of the carburetor. In addition, you can't get a new air horn or choke breaker from the dealer. I rebuilt my carburetor three years ago and I have no intention of doing this. I will have to live with a choke breaker with a bad diaphragm A.

why not drill out the rivets for the CB and auto choke and replace them with screws like you mentioned? wouldn't be too hard.

[Gokhan]

Well, the choke-breaker is riveted onto the air horn; therefore, it's apparently not meant to be removable and replaceable. Perhaps it's possible to remove the bracket the automatic choke and choke breaker are riveted onto and replace both. Otherwise, you would have to break the rivets and then attach a new one with screws. On top of that, removal of the air horn is rebuilding the upper 1/3 of the carburetor. In addition, you can't get a new air horn or choke breaker from the dealer. I rebuilt my carburetor three years ago and I have no intention of doing this. I will have to live with a choke breaker with a bad diaphragm A.

why not drill out the rivets for the CB and auto choke and replace them with screws like you mentioned? wouldn't be too hard.

Yes, drilling out the three rivets on the choke housing would be the way to do it. Then, you can use some screws and nuts to put it back. I still would have to find a working choke breaker and it's quite a bit work. I could probably deal with the inconvenience right now. In Southern California, the engine cold-starting temperatures don't go below 12 C (54 F) too often anyway.

I will also experiment with different ways of cold-starting, such as kicking the gas pedal halfway or less instead of all the way. In any case, pushing the gas halfway after the engine starts activates the choke unloader, which allows the engine to warm up to 12 C without rough idling. I can then drive off normally.

[Rickety Rhino]

Gokhan, I bought the new choke breaker from Rock Auto in Oct 2010 for $97. I drilled the rivets out of the choke housing and replaced them with little bolts and nuts. The lower bolt/nut on the choke housing was a little difficult to get on. I ended up replacing the CB twice, the first time with one from my parts car, but it failed after a few days. The new one was well worth it to me, because in the winter every time I started the engine, I had to give it gas for a minute or so to keep it from dying due to the rough idle, and it belched lots of smoke during that time. Now it starts flawlessly in cold weather.

[Gokhan]

Gokhan, I bought the new choke breaker from Rock Auto in Oct 2010 for $97. I drilled the rivets out of the choke housing and replaced them with little screws and bolts. The lower bolt on the choke housing was a little difficult to get on. I ended up replacing the CB twice, the first time with one from my parts car, but it failed after a few days. The new one was well worth it to me, because in the winter every time I started the engine, I had to give it gas for a minute or so to keep it from dying due to the rough idle, and it belched lots of smoke during that time. Now it starts flawlessly in cold weather.

Thanks for the tips, Rickety Rhino.

My engine is otherwise virtually 100% healthy with other emission components working fine and no oil consumption at all with 0W-20 synthetic (having replaced the valve-stem oil seals). Since I live in Southern California, morning engine temperatures rarely fall below 54 F, under which choke-breaker diaphragm A is really needed, as above this temperature choke-breaker diaphragm B kicks in. While I would love to have a working choke breaker diaphragm A, I will probably not do this repair immediately, as there is a chance of damaging the automatic-choke housing while drilling and it's also quite a bit work. In my case, the engine idles fine if I press the pedal about halfway (with the choke unloader kicking in and opening the choke) and it takes less than a minute for it to warm up above 54 F if it was below that temperature to begin with.

[dlb]

the project terc i have been working on has had cold idle issues that i hadn't figured it out when this thread was revived. the car would fire up nicely, but after a few seconds the high idle rpm would start dropping and end up kind of bouncing around 1300 for a few minutes until it warmed up more and was suddenly fine. i had done the CB tests before and i saw the linkage move a tiny amount so i thought it was ok, even though it seemed like an awfully small movement. i checked the AAP and found it was ruptured so i replaced it, figured all would be fine then, but found the cold idle issue was still the same. after reading this thread, i thought i'd look closer the the CB diaphragms so today i tried sucking on them with a hose, and guess what—both diaphragms are ruptured. too big vacuum leaks! i will experiment with simply blocking the lines that run to the CB and see how it runs like that, and if it's not satisfactory i will replace the CB or the whole carb with my spare. whatever's easier. just really glad that this thread was revived and got me looking closer at the CB.

[Gokhan]

the project terc i have been working on has had cold idle issues that i hadn't figured it out when this thread was revived. the car would fire up nicely, but after a few seconds the high idle rpm would start dropping and end up kind of bouncing around 1300 for a few minutes until it warmed up more and was suddenly fine. i had done the CB tests before and i saw the linkage move a tiny amount so i thought it was ok, even though it seemed like an awfully small movement. i checked the AAP and found it was ruptured so i replaced it, figured all would be fine then, but found the cold idle issue was still the same. after reading this thread, i thought i'd look closer the the CB diaphragms so today i tried sucking on them with a hose, and guess what—both diaphragms are ruptured. too big vacuum leaks! i will experiment with simply blocking the lines that run to the CB and see how it runs like that, and if it's not satisfactory i will replace the CB or the whole carb with my spare. whatever's easier. just really glad that this thread was revived and got me looking closer at the CB.

Also make sure that the diaphragm B adjustment screw is in place; otherwise, there will be a huge vacuum leak. This screw has a tendency to fall off and get lost unless you apply some adhesive silicone sealant on its threads and over its head. Therefore, make sure to apply some adhesive silicone sealant to it if you adjust the screw.

[dlb]

where is the adjustment screw? i haven't noticed it or seen anything in the FSM about it. what does it adjust?

i'm at work right now, otherwise i would just go outside and take a look, and this is really curious.

[Gokhan]

where is the adjustment screw? i haven't noticed it or seen anything in the FSM about it. what does it adjust?

i'm at work right now, otherwise i would just go outside and take a look, and this is really curious.

The adjustment screw is on the front. You can see the original factory yellow thread sealant around it. Unfortunately this thread sealant tends to wear out and if you adjust the screw, the screw will fall off because of vibrations after a few hundred miles and get lost. It will result in a huge vacuum leak and poorly running engine.



The screw has an O-ring attached to it. Use an adhesive silicone sealant around this O-ring and around the threads before you reinstall it. After you reinstall it, apply the adhesive silicone sealant over the screw's head as well. Even if you have never removed the screw, it's a good idea to apply the adhesive silicone sealant over its head just in case it may fall off one day. Something like this should work:



The screw adjusts the diaphragm B and it doesn't seem to be an important adjustment. You can leave it the way it is and not bother with the adjustment and the engine should still run fine when it's cold. However, apply the adhesive silicone sealant over its head just in case.

If the screw is lost, you can cover the hole with the adhesive silicone sealant, the diaphragm B will open the choke to an angle higher than the specified but the engine should still run fine.