I am posting this to help anyone else out with a similar problem starting their manual Subaru. Since the COVID-19 shutdowns, I have had intermittent starting issues. I naturally assumed it was the battery since the car sits for weeks and it is a relatively small battery. And it started fine after I drove it to the store or something. I believe on a couple of those occasions it was the battery. Here were my symptoms:
Cold Start: Key on, lights work, fuel pump primes — click no turnover.
Warm Start: Started every time.
Sometimes I could jump it with another car, but even that was intermittent. Sometimes I could hold the key in the start position and the starter would eventually kick. But, since I wasn’t driving the WRX all that often, it was hard to find a pattern. And disconnecting the battery did seem to help for a while. That is until it didn’t and I had to push start it. The warm start threw me off too.
I checked my connections and they were all good. I cleaned them anyway and it didn’t help. Battery voltage was good too. I bought a booster pack to help start the car and it didn’t help. I was about to replace the battery until I remembered that the starter has almost 200,000 miles on it. And I found this video.
To summarize, the contacts in the solenoid can wear down – a stronger battery can help to bridge the gap – but eventually that too will stop working.
So I bought an open box new Denso starter and it fired up before I even had the key completely in the start position.
Cheers!
B.黒曜石 
It’s funny how you forget that every single part of the car is as old as the things you obsess over, like the engine or suspension. I sourced a used starter from a junk yard, disassembled it and cleaned checked everything, including the solenoid and brushes. Of course I keep the old one on the shelf, it never gave up completely, I replaced it after just a few bad starts, so in a pinch I have an emergency spare. One thing you left out was the warning about how one of the screws securing the starter is 18 feet long.. lol
LikeLike
Those bolts take forever to remove. It doesn’t help that you are trying to keep from dropping the starter. I thought about rebuilding my old starter by replacing the solenoid but Subaru wants $95 for one (p/n 23343AA230) and I found my starter for a little bit more than that.
LikeLike