None of my vacuum accessories are working after sitting for a number of years, any idea where to start troubleshooting? There is zero movement with any of the doors and I have 15" of vacuum coming off the engine.
Thanks

 

 

1970

 

If you don't have a Mity Vac go buy one as your going to need it.

Next plug the wiper door lines where they tee into the headlight system. This allows you to isolate the headlights and get them working before moving on to the wiper doors. This allows you to turn a big problem into two smaller issues.

After that just start testing each of the components in the system, there is nothing difficult about getting the vacuum system working, it just takes a little time checking all the components.

Also a word of warning... check new components before installing them, as about half the Chinese crap arrives not being able to hold a vscuum.

 

Start at the vacuum fitting on the intake manifold and follow the hoses testing as you go.

 

As said, start with the headlights with the wiper "T" disconnected.

http://www.corvette-101.com/vacuum.htm

 

Your first course of action should be to inspect all of the vacuum lines in the engine compartment to see if any 'critters' chewed them up. Also check to see if any have come off their fittings.

If no vacuum-operated system is functioning, I would start by testing the one-way check valve in the main supply line coming from the fitting on your intake manifold. After sitting for that long, the rubber diaphragm gets hard and might be sealed permanently. Remove it and blow gently through it...from BOTH directions. You should be able to blow thru it in one direction ONLY. If it will not pass air in either direction, replace it and many (if not all) of your vacuum problems may disappear.

 

Thanks for the pointers.

 

Finally got the lights to do down! Next trouble shooting the wiper door.

 

The wiper door can be "testy". There are several items that could fail in that system; some are 'safety' items that prevent the system from causing damage to itself.

Willcox has a very nice diagram of that system for various model years; I suspect that you have a 1970-72 model based on your BB moniker. The troublesome items in that circuit are the vacuum/solenoid switch (mounted to backside of the tach housing) and the wiper park safety switch (mounted in wiper well below the right side wiper when parked). The park switch is a common failure item, and new pieces are notorious for being difficult to position properly. But, you NEED this switch to prevent damage from uncoordinated door closings. The switch on the tach is normally reliable; but anything 40+ years old can wear out or fail. There is a vacuum relay in the system that can be a problem. The seals on the [internal] shuttle valve can get hard and shrink allowing vacuum leakage.

In general: The vacuum systems on these cars are SIMPLE, as are the individual devices in the circuits. It is much easier to diagnose and repair than any electrical system designed to do the same work. You just need to find/buy a little vacuum problem diagnostic manual and read it. The vacuum from your running engine is the only 'power' source you need. If your engine won't run, you will need a MightyVac or other manually operated vacuum pump to test lines and components. You cannot test the entire system, nor any individual circuit with a MightyVac. It doesn't have anywhere near the capacity required to do that. But you can test individual vacuum lines or individual components for integrity using it as the vacuum source.

 

Very informative thread!!