I once was called to an old lister genset that had been stood for about 25 years since the farm it served had gone "on the mains". Trouble was they got power cuts every winter, and the farmer asked if I thought it could be got going again.It was in a building, covered in dust but basically sound. Took out the injector, drained and refilled the diesel tank, bled it out, and cranked it..........the injector worked, put it back together again and off it went, lumpy at first, but soon settled down. When it started there was a huge crash on the tin roof as all the water in the exhaust shot out of the "flue and came down again! the change over relays were already installed so we simulated a power cut, put a tractor battery on the start circuit, and as soon as a light was switched on in the house, the genset started, and when the last light was turned off, it stopped. Spent more time cleaning and oiling than I did fixing.