I also buy these units from auction, sight unseen. It’s a gamble, a crap shoot…however you want to say it. Most of the units that I bid on are a few hundred miles away. When and if I win them I’ll go and haul them home with my flatbed trailer, or if they’re trailer mounted I just tow them home. I’ve only really been burned once when I picked up a 803A that was missing the rain cap. It’s always fun to bring these units home, get some coffee and go up to the shop and spend some time on them. I rarely have to spend much time to bring them back on-line. I also had another 803A unit earlier this year that needed some internal engine work. The design on the Lister/Petter engines with the trap door on the side of the block allows you to remove pistons/rods etc without pulling the engine. As Kurt mentioned, inside of the control panel is a series of relays and one “frequency trip switch” that looks similar to the other relays, but is different. Check to see if there’s anything missing and/or in the wrong place. I’ve had a couple of units that were missing one or more of them. Also, one other unit that had the frequency trip switch in the wrong place. I let the smoke out of it when I brought 24vdc up to the panel
The help and guidance from this forum is excellent. Good luck with you!