Stock F2 Choke system confusion

[newindustar]

I don't fully understand the choke system on my stock F2.

1. My choke is always wide open even cold and I don't see what is supposed to close it except the choke cable, why then have a temp controlled choke opener? Someone told me his choke is closed cold but mine is open. My Haynes manual shows choke closed cold and the vacuum bsvd opens it when hot, makes sense but where does the choke cable fit in? Does the vacuum choke opener overide the choke cable if you don't push it in as soon as you should? Or is the choke cable to override the temp controlled opener?

My choke is wide open cold. Is this normal? The Haynes manual says closed cold. What closes it? The only thing I can figure is the choke cable. I can't tell cause my knee broke it when it was pulled out and I was getting out. Is it possible the choke cable can hold it closed cold as well as hot and the choke opener than opens it hot? Really I don't know what is supposed to close the choke besides the cable unless I am missing an external spring but the exploded carb diagram does not show one.

2. HAYNES manual shows the vacuum line going to the choke opener has a tee in the metal part with one end going up to those three ports on the air filter, this makes a constant vacuum leak and there is not enough vacuum on that line to pull the choke opener diaphram. This can't be right, there would never be enough vacuum coming from the air filter can to open the choke. As soon as I plug the vacuum line going to the air filter the choke opener linkage snaps back. Of course in my case my choke is already open. I plugged the line going to the air filter and it runs better without that vacuum leak

Is my Haynes manual correct? It has the choke opener line going to the bsvd which is getting it's vacuum from the little three hose vacuum port in the intake manifold. This would make sense if the steel part of the line did not tee up to the air filter port before going to the temp valve thus losing all it's vacuum pull.



Thanks
Hudson

here's the relevant diagrams:
choke opener circuit.jpg - Windows Live

choke hot and cold.jpg - Windows Live

 

[2mbb]

The choke is manually closed by pulling the cable. If, when the engine is off the choke will not close when the cable is closed, then there is something wrong with the choke cable. But you will have to pull the cable to get the choke to close at all.

The carburetor has at least two systems that will open the choke. The choke breaker system opens the choke a little bit after starting. The choke opener system opens the choke when the engine warms up. The 2F engine manual has procedures for adjusting the choke breaker and opener, but an SST is required, which is a special protractor used to measure the angle of the thorttle and/or choke plates.

The diagram for the choke opener from your haynes manual is correct. The piece that is important is not labled in the diagram, though. There is a restriction orifice in the vacuum lines that connects to the nipple on the air cleaner. It physically looks like a small straight tubing connector, off-white in color. It has a small hole drilled it in. It allows the diaphram to be pulled in when manifold vacuum is applied, but allow allows the vacuum to be released if the BSBV closes. The restriction orifice is shown in the schematic as two opposing triangles, "pinching" the tubing. The restriction orifice is part number 90412-05001 in the attached pdf schematic.

 

[newindustar]

Thanks very much 2mbb. This is the sort of specific response I was hoping for, very helpful.

1. First the choke breaker. I had found someone had the green check valve in backward, I reversed it to restore the 15 second delay. It works the other way but there is no delay, not sure why the want the delay.

2. The issue with the vacuum dumping into air filter housing and not operating the choke opener is what I had suspected. My restrictor is AWOL. I had been wondering if the restriction may have been in the little black steel tube stub on the air filter housing. The Haynes manual showed a restriction it to a degree but never referenced it properly. I am happy you could point out the missing part and supply the part number.

So I have been running a significant vacuum leak for a long time. What a great way to hide a vacuum leak! Silent as well. No wonder it runs better with that hose plugged.

3. I can close the choke manually with the cable and this would imply the choke is normally open cold like mine is.

Two issues here;
a. others have told me theirs is normally closed and
b. Your discussion and these diagrams seem to imply the choke would be closed cold.

So I still have the question "is the choke normally closed cold and if so what closes it"? If it is normally open hot or cold without the cable pulled what is the point of the two vacuum choke openers? Also what is the logic having both manual and automatic openers? Is one an overide for the other?

If we can address point three I will be home free!

 

[2mbb]

As far as I know the choke plate will not close unless the cable is pulled. I think the emissions manually assumes you have pulled the choke cable. As you implied earlier, if the choke closed automatically you wouldn't need the choke cable at all. There are actually two parts to choke. One is the choke plate that is observed at the top of the primary throttle bore. The other is the fast idle setting, which essentially opens the primary throttle bore to increase idle speed when cold. Both the choke opener and choke breaker systems only open the choke plate. The only way to reduce the idle from fast idle to normal idle is to push the choke cable in.

 

[newindustar]

I see you've got a fine year for you FJ60. I appreciate the piping schematic, I did not have it.

I think you reply was spot on.

I closed the choke with the cable watched as it warmed up. First the choke breaker cracked the choke open within the 15 second delay, then I watched after it warmed a bit as the bsvs opened and the choke opener pulled open the choke the rest of the way or very close to it.

So both the choke breaker and the choke opener have the ability to override the pulled choke cable.

I see three possibilities why they designed it like this.

1.The first is emissions so the choke breaker will prevent an over rich mixture spewing out the exhaust on cold start.

2.The second is like the first in case you don't happen to push the cable in as soon as necessary it'll open the choke at just the right time for you say if you ran back in the house for you coffee after a cold start and you did not get back promptly to push in the choke

3.The third is that you are able to have a fast idle via the pulled choke cable as a throttle cable does even when hot. Besides cold starting this is nice for running a winch or pto or any other reason you might want your rpms up without choking out the engine. This is in effect a clever combo throttle and choke cable, old trucks also had them seperately which is a nice setup as less to go wrong.

So we have all the theory matching, the odd thing is before I did the above for the first time I saw the choke closed cold by the coil spring on the end of it's shaft cold with the choke pushed in. I am just going to pretend I did not see that. it is not doing that now, yikes, don't need my theory blown!

 

[2mbb]

I don't think Toyota planned on #3, since they offer a separate "throttle cable" to increase RPM's for winching, etc. As stated in the diagrams above, both the choke opener and choke breaker are used to prevent an overly rich mixture and therefore improve driveability. I don't think it's strictly an emissions thing since emissions testing is always done with the engine warmed to operating temperaure. Your #2 is just an added benefit.