Question About Vacuum Starter Switch

[Guest shadetree77]

I will be putting the original generator back on my 52 sometime in the next month or so. Right now, it's running off of an alternator and is started by a push-button switch mounted under the dash(all done by the previous owner). I want to hook up the pedal actuated vacuum switch on the carb when I install my re-built generator. I've read over the service manual section on how the switch operates and I have a question about it. It says that when the car starts running, vacuum from the manifold pulls the metal ball inside the switch upwards into a passage which breaks the contact in the switch and doesn't allow the starter to engage the next time you depress the accelerator. So my question is, where does that manifold vacuum come from? That is to say, how does it enter the switch? What I'm worried about is that if this vacuum is the same vacuum that is supposed to cause the automatic choke to work I might be in trouble. Reason being, the choke doesn't work right and I've narrowed it down to a vacuum problem. I'm worried that if these two systems work off the same vacuum and I try to start the car, the ball inside the switch won't move and my starter will continue to activate every time I press the accelerator!! I can just hear the grinding now!!:eek:

Edited December 12, 2011 by shadetree77 (see edit history)

[Ben Bruce aka First Born]

Robert, I can't remember if you obtained a Shop Manual or not. You should find the answer in there. Having said that, which carb do you have? May make a difference. I will go to the garage a little later and get my manual and scan in the info.

Ben

[Guest shadetree77]

Ben, I do have a service manual and I read over the section on the switch but it just says "manifold vacuum". From what I can tell there's no definitive picture or description of just where exactly that "manifold vacuum" comes from on the carb. I have a Carter WCD 2 Barrel #882-SA. Perhaps it would be located in a different part of the manual? Not sure which section it would be in though. I appreciate the help. Let me know if you find anything.

[Ben Bruce aka First Born]

Hi Roberet

My manual is for a 1950, so may or may not be the same. Best I can tell, your switch is mounted low , on the throttle body of the carb. My Super has a Carter, and that is the way it is mounted. This would utilize vacuum directly ftom the intake manifold. The chock, on the other hand, is mounted higher, and gets its vacuum from the "horn".

More info in the carb section.

Ben

[old-tank]

1956 Century:

The Buick accelerator starting system used two safety features to prevent the starter from actuating once the engine was running. One is that vacuum from the running engine would lift a ball in the carburetor starting switch and this would prevent the switch contacts from closing thereby preventing the starter relay coil from closing the relay points and then actuating the starter. The second safety feature was to obtain ground potential for the starter relay coil by connecting the coil lead to the generator armature terminal (either at the generator or on the ARM or GEN terminal of the regulator). When the engine is not running, the armature terminal is at ground potential (-12 volts). However, once the engine starts, the armature terminal now has + 13-14 volts on it and so the coil of the starter really cannot function since it cannot get a return path to ground. Once you install an alternator, you lose the second safety feature. I would suggest that you ground the starter relay lead that formerly went to the generator armature . The car will start if the rest of the circuit is OK. I would also add a toggle switch, under the dash, in the circuit in series with the carburetor switch. Now, in case the carburetor switch malfunctions and the starter continues to operate after the engine has started, you can simply throw the toggle switch to the off position to stop the starter from running.

To understand this you should study the shop manual wiring diagram or get a copy of the Buick Bugle article I wrote on these systems.

Good Luck.

Joe, BCA 33493

Previous excellent explanation. Even if the vacuum system fails it should not continue starting

[carbking]

The choke normally would be non-functional if the internal carburetor vacuum passage is clogged. This passage has nothing to do with the starter switch.

Jon.

[Guest shadetree77]

The choke normally would be non-functional if the internal carburetor vacuum passage is clogged. This passage has nothing to do with the starter switch.

Jon.

Thanks Jon. That's pretty much what I needed to know. I was just worried that they might work off of the same vacuum source. I should be ok to try that switch out then. Thanks for all the responses guys!