Hi everyone. I trying to adjust the automatic choke on my 403 and i found out this : vaccum connector without any hosing. See picture. Any idea ?I feel vaccum suction when i put my finger on.

Pat

 

If you feel suction, that is probably a vacuum leak. You will want to put a cap (rubber vacuum cap) over it short run. If your engine runs rough or badly, this could be one of the problems.

It looks like your car is a blend of multiple generations of Olds technology. That is not a problem, but it means that you should understand how the parts fit together.

The blocked off 3 ports in your intake manifold were intended to provide heat to the choke coil on your carburetor. As the engine runs, the intake heats up. A tube connecting the middle port (the one with the big screw in it) is supposed to be a tube that transfers heat to the choke coil and allows it to unwind or relax allowing the gas mixture from startup rich to somewhat leaner ordinary operating temperature.

You have at least 2 choices to build a functional choke mechanism: 1) stay mechanical and repair the heat transfer tube from the intake to the carburetor or; 2) switch to electric choke as Olds used in the late ‘70’s. If you go with solution 1, you will need to form and vacuum seal a small diameter (perhaps 1/4” or maybe 3/8” inch _metal_ line between the intake and carburetor. Be certain you use metal to connect the carb to the intake, rubber will not transfer heat, so it will not allow the choke coil to relax as the car warms up.

If you choose to switch to an electric choke, you will need to vacuum seal the hole on the passenger front of the carb where the choke housing connects to the body of the carb. But you will also need to be sure that the choke is grounded (i.e. has a - electrical connection)

J’espere que mon anglaise est clair et plein. Bienvenue!

Chris

 

Thanks Chris for your reply.that means i'll have to connect one of the holes (ref 1) to the thread (ref 2) on the picture. I've got copper pipe and connectors for break circuit. I could try to build somethings with.

 

By the way, it's at the point 2 where i feel vaccum suction.

 

For a mechanical choke, vacuum at the point 2 is normal. There should be a vacuum tube which connects the front lower choke assembly to the body of the carb which eventually connects to manifold vacuum. This is the force which pulls manifold head from the intake (as it warms up) into the choke coil and allows it to relax (and work). So suction at point 2 is normal. But this part is missing on your car, so it’s a good idea to recreate it in metal.

It is important that the point 2 is connected with no vacuum leak to the manifold center port so that it conducts heat to the choke coil and does not permit atmospheric air into the carb. By this I mean that the manifold connection and also the carburetor connection must be sealed against vacuum leaks to work properly.

I hope that is clear. For a quick fun test, try putting a vacuum cap on your point 2. If the car runs better, you have solved one vacuum leak. The second challenge is to make the choke operate properly. For that you will need to form/bend a metal pipe between the intake manifold and your point 2.

My best wishes for success with this project. It should be an enjoyable project.
Chris

 

I have both a '77 and '78 Toronados with 403 engines. You are missing part of the choke tubing. See the photo below. The tubes you need are available from Fusick. You can buy the entire piece that fits inside the intake manifold as well. I found that I had to bend slightly the part that sticks down in to the engine because Fusick doesn't show it as actually fitting a 403, and it doesn't. But it's very close and can be made to work.

The other tube coming up out of the manifold goes to the rear and connects by rubber hose to the carburetor.






Here's what Fusick offers.

The upper, p-trap-shaped tube should fit onto your choke exactly.

https://www.fusickautomotiveproducts...umber=CTB40/43







This is the part that sticks down into the manifold.

https://www.fusickautomotiveproducts...p?number=CS642

 

No wonder it isn't working right. I would buy all the parts shown. At minimum pull the piece in the manifold. I have seen those rotted through and the choke not working properly because of it. A simple fix snd adjustment when cold. If it is still won't set right, the hot air choke coils still fail occasionally. Good luck.

 

By the way, here's what the manifold choke tube looked like when I pulled it out of the engine. The tube itself was still intact, but the point where the exterior tubes are press-fit into the bracket was rusty, and the tubes that had been in there had broken off, so it couldn't be reused.

You can see, though, that the U-shaped tube is not exactly the same shape as the Fusick replacement. But I was able to bend it carefully, and, with a bit of trial-and-error, was able to get it to fit.

 

In looking at the choke tube mount on your car, it looks just as rusty as mine was. Be careful loosening the two bolts. I broke mine off and ended up drilling and tapping new holes right on top of the old ones.

It also looks like someone jammed some screws into the two tube openings. There was no reason to do that because that's just a u-shaped tube that is not connected to anything. No vacuum leak here. Unless there was reason to believe that the other side, u-shaped tube was damaged, rusted, or missing. Then you might have a manifold vacuum leak.

 

Actually that would be an exhaust leak since the tube is in the exhaust crossover passage.

 

Thanks! I figured it would probably be some kind of leak.

 

And this won't be an issue or very useable for those that block off the crossover.

The crossover heater tube simply takes filtered air from the back of the carb where yours has a little rubber plug on it (you can see the tube opening through the top of the carb), and it is drawn through the tube system through the choke heater tube, through the choke housing (now heated) and into the front drilled leg (may have a plastic orifice tube) of the choke mounting point into the carb which is under full manifold vacuum. It is designed to leak a measured amount to draw heated air in to relax the choke spring and keep it relaxed so it's constantly drawing in air. Yes, you can plug it, but then if you want your choke to work correctly, then consider investing in an electric choke conversion kit. Or if you fix it to be a hot air choke, use the kit aforementioned.

 

Another option is to Go Electric. Replace housing cover with electric. Disgard housing cover paper gasket. Rubber cap on #2 hot air inlet fitting. 12v source with "KEY ON" power only.