80 project

First off. I have an 85 GSL carbed. When I pull the choke and start the car, it stumbles and bucks and blows lots of smoke out the exhaust, but it runs. The choke is fully closed. I found a solution to this but I am not sure what I am messing with. There is a diaphragm with two vaccume lines and a linkage to the choke assy on the back of the carb just under the air cleaner. When I push the plunger into the diaphragm and start the car cold with the choke pulled, it runs much smoother and revs about 2500. I made up a bracket to keep the plunger permanently into the diaphragm.

Now I have to pedal the car to get it to idle until it is warmed up.

What is happening, is the choke plate is opened slightly when the choke is pulled, by means of holding the plunger into the diaphragm.

I hope this is not too confusing.

The car runs great when warmed up. It has new plugs, wires, cap, fuel filter, and the timing is dead on.

Sterling

It sounds like the solenoid that is supposed to open that pot is either not hooked up, not making good electrical contact, or there is a vacuum leak present in a cracked hose.
As I understand it, when the bimetal spring gets warmed up enough, it's supposed to cut electric to the electromagnet that holds the cable out. But vacuum is supposed to actually pull the choke all the way open via that pot diaphragm.

I'm not as familiar with it all as Carl, I think. I tend to rip all that **** off, and just foot it till she's warm. I never put her in gear till she's fully warmed up.

80 project

I checked for vacuum leaks and made sure the electrical connector was hooked up. The pot plunger has more resistance when the choke is pulled out all the way. assuming that this device is not the problem, why would my car sputter and not idle high when the choke is fully closed at cold start?

Montic

Mines doing this same thing. It will die when if I dont give it gas with the choke fully pulled. I just pull it half to 3/4 and let it warm up from there.

Sterling

There is a "high idle" linkage set-up on the main linkage, but I don't know much about it. I do know it is adjustable.

Rx7carl

The choke heater comes into play as the car warms up. Its independent of anything else. The valve your messing with IS where your trouble is. That is supposed to allow the choke to pull open and allow some air in based on vacuum (basically when the choke is pulled closed and you rev the engine, that plunger is supposed to pull the choke open based on manifold vacuum so some air can get in, and then allow the choke to close when you let off the gas). The fast idle rod doesnt come into play until after the choke plate is closed. It is the rod that goes down from the choke to the main throttle linkage. Its actually adjusted by bending the rod. Sounds to me like either the choke valve is bad (unlikely), or the choke heater spring is not hooked to the choke tab correctly, making it hard to impossible for the valve to pull the choke open. The spring inside the heater (in the slot you can see) has a hook on one end, which the choke rod tab fits into. When installing the heater, you have to pull the spring a bit (in the tighteneing direction) to hook the choke into it, then install it. If you just stick it on, the spring will be on the wrong side and cause the choke to not want to open from the valve. Man its really easy to show someone this, but hard as hell to describe.

80 project

Thanks for the info guys. I will check to see if the plunger retracts with some throttle. If the fast idle rod was not adjusted correctly, would this cause the pig rich starting condition?

It seems that by opening the choke just slightly from the fully closed position by means of pushing in on that plunger,(but still having the choke fully pulled out) I get the best cold start. I just tried it. It reved about 1700rpm with very little drama.

Could it be that the amount of vacuum on start up is not pulling the choke plate open enough to allow the proper amount of air into the carb? This is what it seems like to me.

80 project

I dont know if this is important, but my choke does not return on its own after the car gets warm. I have to return it manually.

Rx7carl

The fast idle doesnt come into play till after the choke plate closes. Yes, the choke isint being controlled by that plunger like it should, thats why holding it open a bit is helping (its keeping the choke from choking off ALL the air to the engine).

As for it not returning, theres a temp switch on the back of the water pump housing. When the water reaches a preset temp, it drops a ground for the electromagnet on the choke control. You either have a bad switch, or someone hot wired it. Thats what I did on my racecar so I can control it manually. Actually thats where my water temp sender for my new gauge went so I had to do this.

80 project

So whats the fix? I checked for vacuum leaks, found none. I lubricated the plunger shaft. I checked the wire that goes to this unit and the connection. Do I need to replace this diaphragm? Is there a sure fire way to test it out?

Rx7carl

Yes, if you look in the Haynes or whatever manual you have theres a test for this stuff. See if you can remove just the choke heater and see if thats whats causing the problem.