A cartridge starting system is also fitted to the tractor. A shot-gun type cartridge is loaded into a breech on the engine's intake system. The smouldering paper is placed in the cylinder head, and the cartridge is fired by tapping the protrusion pin with a hammer. This puts a charge into the bore, sending the piston through its stroke, bursting into life. This method, however, deposits carbon which often causes jamming of the decompression valve if cartridges are regularly used. It also puts significantly more strain on the engine.
Later versions of the Field-Marshall had more sophisticated starting systems available - electric starters were optional on the Series 3As.