My 1990 240 wagon has had intermittent starting problems for about 6 months. Most often it starts right up. On occasion (most often but not always after sitting for a while, or driving for 2+ hours straight), nothing happens when key is turned (I can just here a very slight/soft whir). In such cases (nearly but not always), I can leave the car sit for about 15 minutes and then try again and it will commonly fire right up, or it will start after a few second delay when the key is held in the far right position. Here's what I have looked into so far:

-Starting car in neutral and/or wiggling shifter doesn't seem to have any affect (ruling out neutral safety switch)

-Connecting starter test terminal to negative battery terminal produces the same faint whir as when the key is turned and it doesn't fire up. Something is happening when this is done, but I don't know what it is, what it indicates. Again, I just hear this faint whir when I touch the positive terminal with the wire, and then nothing when it's lifted off.

Next move would be to connect starter solenoid to battery but (i) I'm not confident I will be able to locate the correct terminal in the engine compartment and then get a wire on it and (ii) I'm not sure what should happen and what it would even mean? (if the car starts, does that indicate the ignition switch is faulty, and it not, the starter is on it's way out?).

Any guidance would be appreciated. I think I'm on track, just hitting some road bumps due to lack of expertise.

-John