After a year long search for an electrical gremlin in my XJS, I finally found it. My starter switch seems to be causing the problem. The car sometimes won't crank, and when it does it is often slow. Other days it is just fine. I just figured out that when I apply downward force on the ignition key, the engine always cranks. It is time to replace the ignition switch. There appear to be two parts. One is just the electrical switch, and the other appears to be the electrical switch plus the mechanical switch. Am I safe replacing only the electrical switch, or does the XJS typically have problems where I'm better off replacing both the electrical and mechanical components? I'm asking in case the mechanical switch has insulation or something else which could be damaged and causing problems.

 

Just do the electrical portion. You will be fine.

 

Will do. Thanks.