Starter Switch Doesn't Start

nehmo54

This is a Mercury Sable 2001, Vulcan engine 3.0L, Sedan body
The electric of the car functions normally except occasionally, the ignition switch doesn't work properly.
When the key is in the run position, all the accessories work normally.
When the key is in the start position, nothing happens.
I sometimes can turn the key back and forth, and then the switch works normally.
Once started, things are fine.

I replaced the neutral safety switch, and nothing changed. This was some months ago.
Later I changed the electrical part of the ignition switch, the part under the column on the left (driver's POV)

Still, the problem recured occasionally

Since the car usually starts with playing with the key, I just lived with the problem. Now, it seems to have gotten worse.
When the problem did occur once, I jumped the starter, and it turned over properly, but the engine didn't start.
To make the repair difficult, I can't cause the problem at will. Usually, everything will work fine.

So, what's my next troubleshooting step? Should I just change the ignition switch again? Ideas?

Mr_Shiftright

I would check the starter solenoid (which is a relay). As you turn the key you should hear an audible "click".

You may find this VIDEO helpful

nehmo54

Mr_Shiftright said:

I would check the starter solenoid (which is a relay). As you turn the key you should hear an audible "click".

When I use a jumper wire to the small wire of the starter (starter has small wire, big main wire, and ground), the starter turns fine, but the engine doesn't start. I think the big solenoid is on the starter. I'm not sure if there's a relay in the junction box under the hood.
I just tried it, and it's working normally. I'm going to buy another switch as a precaution. But I suspect maybe the key mechanism isn't moving the starter switch properly.
I really need to go to the store. We have lots of animals, and we're out of food. I'm headed out now.
If I had a good electrical schematic, it would help.

Mr_Shiftright

TRY THIS DIAGRAM. You have to scroll down the page to see it. Seems to have what you need.

nehmo54

So if I want to start the car, and the ignition lock cylinder doesn't work, I can make terminal 75 hot with a jumper? (Plus I need to jump the starter, which I know how to do.)

nehmo54

It seems the problem was with the key itself, which is a copy of a transponder key. (In this case, the copy is called an "electronic key". It's not a very descriptive name. It's an aftermarket key that requires a battery in the key head.) I replaced the coin battery in the key head, and the problem hasn't reoccurred.
I still haven't figured out how to bypass the "engine disable" system. IOW, I haven't figured out how to get power to the engine without using the transponder-like key.