I have trouble starting. Sometimes it will start with no problem then the next time I try to start no go. The unusual thing is that sometime I can start it for days with no problem then it won't. I have charged the battery and wonder if it could be the starter or the ignition. My questions are: Can a starter be intermittent and be causing the problem? Can the ignition system be the problem? After 238000 miles the key switch itself is worn to some extent. I want to know which part I should buy and not have to buy Iqnition system, starter system or something else. Thank you.
First you have to clarify the symptoms. "Doesn't start" can mean a dozen different things. If it was as simple as "buying a part" based on symptoms, we wouldn't need mechanics to diagnose them. Even the parts you mentioned indicate problems in two entirely different circuits so as a guess, I'm going to suggest the starter doesn't crank the engine. If that is right there is no need to be thinking about the ignition system. It's not even in the picture yet. One common problem on Fords is the heavy cable going to the starter has multiple strands of wire corroded away under the insulation. There is even a foot note to that effect in most replacement starter catalogs.