9N feeling tired

Hi ya folks,could do with some advice about my Pet/Ker. 9 N. I had her out yesterday at the local Folk Museum where there was a Ferguson Club working day. ( sorry to mention Ferguson on the Ford site,) . :lol: This was the old girls first run out this year, and when I put the battery in, the starter did not engage with the flywheel, so I took it off and freed the bendix and oiled the threads. When I put it back ,it only started her once and then free wheeled again, so had to swing her by hand. At home, first lift and away she went, but as usual when I had spectators, not a Kick
so reverted to a tow. Once going she ploughed all afternoon, no problem. Can anyone tell me what might be wrong with the starter, couldn't see anything obvious when it was off.
Although the old girl goes reasonably well , oil pressure when warm is in single figures, would it help to fit in a set of shells and possibly a new oil pump? I don't really want to spend a fortune as she is only out a couple of times a year ,any idea how much this would cost? Any advice appreciated Paddy. PS originally 6 volt, but now runs on a 12 volt coil and battery.