Perkins 900 Series Diesel Engines Workshop Service Manual
General description
The timing gears are stamped with timing marks (A) to ensure that they are assembled correctly. The stamped teeth of the crankshaft, camshaft and fuel pump gears will be aligned with the idler gear when number 1 piston is at top dead centre (TDC) on the compression stroke. The marked teeth of the idler gear may not necessarily be aligned in this position, because of to the different speeds at which the gears rotate. Perkins 900 Series Diesel Engines.

TDC on number 1 cylinder can be found by the alignment of holes in the backplate and the flywheel.
The two types of fuel injection pump available are both timed at TDC on the compression stroke of number 1 cylinder. There is no timing mark on the rear face of the timing case, but there is a mark on the flange of the fuel injection pump.
Both fuel injection pumps have a lock screw (B1) that locks the shaft. When the lock is applied before the pump is removed, it is not necessary to time the pump to the engine if the crankshaft has not been rotated.

Perkins 900 Series Diesel Engines Workshop Service Manual

TDC on number 1 cylinder on the compression stroke can be found by the alignment of a hole in the flywheel with a hole in the backplate.
1 Remove the rocker cover, see Operation 3-1.
2 Loosen by two or three turns the setscrews that retain the atomiser clamps or release the gland nuts if threaded atomisers are fitted.
3 Rotate the crankshaft clockwise, when seen from the front, until the inlet valve, the first valve, has just closed. There is a slot (A1) in the left side of the backplate, seen from the rear, to give access to the starter ring. A suitable lever (A2) can be used through the slot to rotate the flywheel.
4 Insert the locking pin (A4) into the hole (A3) below the slot in the backplate. Continue to rotate the crankshaft clockwise slowly until the pin enters a hole in the flywheel. The engine is now set at TDC number 1 cylinder, compression stroke.
5 Remove the pin from the flywheel and the backplate.
6 Fit the rocker cover, see Operation 3-1.

Perkins 900 Series Diesel Engines Workshop Service Manual