Pull a plug wire & stick a piece of metal in it or pull the boot back. Set it a short distance from the engine with insulated pliers. If this system is working right it should throw a spark like a bolt of lightning. Be careful it will bite. If the timing changes when you hook the vacuum line to it the vacuum advance is OK. If the timing advances as you run the engine faster then the mechanical advance is working. Set the initial timing with the vacuum hose off.
