Home › Forum › Ask A Member › Anybody test a vacuum cut-out? ’57 Lark › Re: Anybody test a vacuum cut-out? ’57 Lark
The cut out is often overlooked. WHile it is rare that they fail, when they do, they are often not thought about, and the owner is left struggling to determine why they are only running on 1 cylinder. I personally can only think of a couple that I have ever had to replace. I do dismantle and inspect during my restoration process however.
To test, I install my vacuum pump (same one I use for testing gearcase). I connect my audible continuity meter between the center post, and the ground. Increase vacuum, and you should eventually get continuity. Of course, if there is continuity without any vacuum at all, it is bad or shorted somehow. If you cannot short it out even with full vacuum, the diaphragm is usually petrified as Frank stated.
I cannot remember what amount of vacuum activates the plunger fully to short out, but I can go down and run one quickly to find out.