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.