Starting fluid is a volatile fluid that helps get stubborn engines started. It's commonly used on carbureted engines in cold climates. You should be able to find starting fluid at any auto parts store. It comes in a spray can like carburetor cleaner or brake parts cleaner... either of which should also work in tracking down vacuum leaks. KEEP THE SPRAY AWAY FROM SPARK PLUG WIRES AND THE COIL!

Sixto
91 300SE
81 300SD