BLOCK 4I3811 - Caterpillar

LEFT SIDE OF ENGINE (953 ENGINE)
1. Injection pump. 2. Injection pump housing.When plunger (6) is down, fuel in manifold (3) goes through inlet passage (9) and fills the chamber above plunger (6). As camshaft (11) turns, lifter (7) and plunger (6) move up. The plunger closes off inlet passage (9). The pressure of the fuel in the chamber above the plunger increases. At 1170 kPa (170 psi) check assembly (4) opens. Fuel flows to the injection nozzle until plunger (6) moves up enough to open inlet passage (9) to the pressure relief pasage cut in the plunger. The pressure in the chamber above the plunger decreases and check assembly (4) closes.If the pressure in the injection line is above 6900 kPa (1000 psi) a small check valve at the center of check assembly (4) opens. This lets fuel pressure in the injection line go down to 6900 kPa (1000 psi). In between injections the injection line pressure goes down to manifold pressure through a scratch on the face of check assembly (4).
CROSS SECTION OF FUEL INJECTION PUMP AND HOUSING
3. Inlet manifold. 4. Check assembly. 5. Pressure relief passage. 6. Plunger. 7. Lifter. 8. Gear. 9. Inlet passage. 10. Fuel rack. 11. Camshaft.Governor movement of fuel rack (10) causes rotation of gear (8) that is fastened to plunger (6). Pressure relief passage (5), on the plunger, is designed so that when fuel rack (10) is moved in the fuel on direction the period during which inlet passage (9) is closed increases. The longer the inlet passage is closed, the larger the amount of fuel which will be forced through check assembly (4).Automatic Timing Advance Unit (953 Engine Only)
On the 953 engine, the automatic timing advance unit (5) is installed on the front of the fuel pump drive shaft.The weights (1) in the timing advance are driven by two slides (3) that fit into notches made on an angle in the weights (1). The slides (3) are driven by two dowels (4) in the hub assembly of the gear assembly in the automatic timing advance unit (5). As centrifugal force (rotation) moves weights (1) outward against the force of springs (2), the movement of the notches in the weights (1) will cause the slides (3) to make a change in the angle between the timing advance gear and the two drive dowels (4) in the hub assembly. Since the automatic timing advance unit (5) drives the fuel pump drive shaft, which is connected to the fuel injection pump camshaft, the fuel injection timing is also changed.
AUTOMATIC TIMING ADVANCE UNIT
1. Weights. 2. Springs. 3. Slides. 4. Dowels. 5. Automatic timing advance unit.Injection Nozzles
TOP OF ENGINE (VALVE COVER REMOVED)
A. Fuel injection nozzles.The fuel injection nozzles are located in the cylinder head. There is one injection nozzle (A) above each cylinder. The operation of each is similar.
FUEL INJECTION NOZZLE
1. Cap. 2. Lift adjustment screw. 3. Pressure adjustment screw. 4. Locknut for pressure adjustment screw. 5. O-ring seal. 6. Fuel inlet. 7. Compression seal.