Don.
The airstarting of the GW engines and almost the same on the MAN was a bit different. Referring to plate 29 below : Each engine had a starting air flask topped up from the HP system. Each cylindercover had a starting air valve which in the starting sequence was engaged with starting cams on the camshaft by a pushrod. The valve had two airconnections, one at the top for pneumatically pushing the starting valve pushrod in contact with the camshafts starting cams. The other air connection is the startingair supply to the cylinder. The starting procedure is done by the starting handle on the maneuveringstand and the mainstarting supply valve having a handwheel ( painted red on U 995). The main starting supplyvalve is opened, starting handle is put in start position , air is admitted to the top of the cylinder startingvalve, pushing the valve rod against a springpressure down to the startingcam on the camshaft. One of the cams is always in a startingair lift(open) position thus admitting startingair to the cylinder and the engine starts to run on air, by the starting valves. As soon as the engine achieve satisfactorily revs you move the fuel handle and fuelrack of the fuelpumps, admitting fuel to the cylinders and the engine starts to run on fuel. Then you put the starting handle to "neutral" the air on the top of the startingvalve is vented and the spring pushes the valverod up and disengage the connection to the camshaft. As plate 29 shows the system of the direct reversible engine, the real execution of the modified nonreversible execution is slightly different, but the idea is the same.