Cruise control not working

The way this system works is there is a vacuum reservoir that will maintain vacuum to the system in the even there is no engine vacuum like in wide open throttle situations.

However, if you have no vacuum at all at the port and the cruise doesn't work then I suspect we have a restriction or a leak in the vacuum passage.

What I would do is use a vacuum pump and connect it to this port and see if the passage will hold a vacuum. If it does, then there could still be a restriction. However, if it doesn't then that points to a leak in the system so at least we can rule that out.

https://www.2carpros.com/articles/how-to-use-an-engine-vacuum-gauge

I am attaching the info below on this system so take a look at this and let me know what you find.

Thanks