2003 Forester won't start (a second time) in the cold

With the very cold weather I’m having problems getting my car to start again after it’s been running a while–starts okay initially no matter the temp, run it for ~15 minutes then go to my first work stop. One hour later sitting outside in 0F and I can’t get it to start, won’t turn over. Just got a new battery, had the spark plugs/starter/fuel line checked “looks okay”. Starts after it gets really cold again, needs to sit out for a few hours in the single or negative digits. Any suggestions? Dealer is 100 miles away and I have not been happy with the service there.

Do you mean by “won’t turn over” that it cranks ok with the key in “start”, but it doesn’t catch and run? It’s likely one of these: Fuel pressure, leaky injector, ignition component (e.g. crank or cam sensor). My first guess would be a cam or crank sensor on the fritz, as these are often heat sensitive. Has your mechanic tested to see if a spark is getting to the spark plugs when this happens? If so, it wouldn’t likely be either of those two sensors then. If the fuel pressure is ok, my next guess, I’d suspect the leaky injector. It would be consistent with the symptom, starts ok when cold, but not when hot. What happens is the injector(s) leak gas into the combustion chamber after the engine is turned off. This creates too rich of a mixture for a warm engine to start, but for a cold engine – which needs more gas to start – it works ok.