I pulled the air filter out and replaced it with the same OEM (Donaldson PN 181050). It was not clogged up but it was dirty.When you turn the key to start the pull in circuit pulls the solenoid and opens the valve. When you turn the key back to the run position the hold in circuit kicks in and holds in open while it is running.
I also found the temperature sensor on the thermostat housing “terminal” had some play - looks like it was over tightened and terminal may have broken inside. It has one wire terminal connected to the stud, which is tightened, but the terminal lug on the housing has some play. I don’t know the part number. The gauge indicator on the mower panel reads from 0-280 degrees (f).