Vacuum Starter Switch on Restart

[Shootey]

I know much has been written on the throttle vacuum starter switch. I have a basic question. The switch on my 1941 Stromberg works fine on the initial startup. But when I shut the engine off (or kill the engine because I mess up my clutch work) I can’t immediately restart the engine. If I leave the engine off for several minutes it will restart. With a warm engine I was able to restart it within 30 seconds. What’s going on?

 

I have an NOS replacement switch I could install. But I want to understand the operation or inoperation before I do that. Thanks. 

[Buick35]

Maybe a faulty diaphragm causing a leak? I have a nos one on my 35 and so far it works well. Engine vacuum after it starts is supposed to open the contact points to prevent it from engaging the starter when running.At least I think that's how it works.

[1937 Buick 66C]

Greetings all,

 

The vacuum start system that Buick35 describes differs from the later systems that Shootey is working with, which have the starter interrupt switch built into the carburetor.  The 1935 start circuit is more similar to what is on the '37 and '38 cars that use a vacuum switch, mounted to the intake manifold, not on the carburetor.

 

I suggest that Shootey make sure that all of the passages in the carburetor that provide vacuum to the starter switch are very clean and free of varnish.  If I recall properly, there is a ball-type valve that opens the starter contacts (starter cannot run) when engine vacuum is present.  From the Shooty's description of the problem, I suspect that the ball is not moving freely (varnish?) and does not quickly return to its proper position, closing the start circuit.  It may require removal of the carburetor in order to fully and completely clean out the vacuum passages in the carburetor that enable the starter to operate properly.  It may be helpful to locate an exploded diagram of this carburetor to understand how the vacuum flowing through the carburetor operates the starter switch.

[Shootey]

There are two 1941 switch versions. The built-in one @1937 Buick 66C refers to is for the Carter carb. The Stromberg switch is a separate unit bolted onto the carb. Mine is a Stromberg. 

[Shootey]

I replaced the switch with the NOS  one. It works fine now. I did run a pipe cleaner into the vacuum orifice of the carb.