Old Subaru Outback Won't Start Reliably

Bought a used '96 Subaru Outback Wagon w/ 175k miles a few months ago and I’m having trouble. The car always starts when it’s cold. However, sometimes when it’s hot, it won’t start. Then wait 10 minutes or so and it starts right up.

I’ll make a short stop somewhere (like to pick up milk) and when I get back to the car everything seems to work fine: fuel pump, radio, AC, lights, instrument cluster, etc all turn on. Then, when I turn the ignition switch to start, I hear the click behind the dash (starter relay?) and the solenoid clicks but the starter does not turn on at all. Then I wait a little while and it will (almost always) start with no problem. This happens ~25% of the time when the car is hot.

I replaced the starter with a new one (not rebuilt) but that doesn’t fix the problem. I tried hitting the new starter with a mallet but no luck. Battery, alternator and starter checked out OK at the Autozone.

Haven’t been to the mechanic because that would probably end up costing more than the car is worth. I’m grateful for nay help you might have. Thanks!

Get a multimeter, set it to read volts and measure on the starter connections and ground while starting. There’s a fat one that should always have 12V on it.
The thinner connection should only have 12V on it when you’re trying to start.

If you’re not seeing the latter voltage, it could be an interlock somewhere. There’s one on top of the transmission that will not let you start it out of park.

My 88 VW GLI did a similar thing.

It turned out to be a simple $25 repair replacing the ground strap for the engine. Basically a the connection from the (-) negative post on battery to engine block and car chassis. I think DIY is possible but cheap by local garage.