DOOR AS 2244998 - Caterpillar

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Front View of Timing Advance Unit (1) Timing solenoid (2) Timing position sensor (3) Bellcrank
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Timing Advance Unit Before Any The Timing Advance (A) Pressure oil (B) Blocked oil (C) Drain oil (1) Timing solenoid (4) Sleeve (5) Valve spool (6) Ring (7) Gear (8) Carrier (9) Fuel injection pump camshaft (10) Body assembly (11) Bolt (12) RingThe timing advance unit connects the drive end of the fuel injection pump camshaft with the timing gears in the front of the engine. The unit uses engine oil pressure to change the fuel injection timing. An electronically actuated timing solenoid (BTM) controls a double acting hydraulic servo. The double acting hydraulic servo directs engine oil that is under pressure to either side of the drive carrier. The side determines if the timing will be advanced or if the timing will be retarded. The total timing advance range is 25 crankshaft degrees.Timing is controlled by the PEEC III system as a function of the following conditions: engine rpm, load demand (rack position), boost pressure, engine acceleration and throttle position. A timing position sensor is used for accurate feedback control of the timing advance through the ECM and the timing solenoid (BTM). Timing position sensor (2) is located on top of the timing advance actuator housing. Bellcrank (3) is used to transfer linear motion of the timing advance unit to the end of Timing Position Sensor (2). Bellcrank (3) is in contact with a thrust bearing. The thrust bearing is fastened to the timing advance body assembly (10) and the thrust bearing follows the movement of the timing advance body assembly (10) .The timing solenoid (BTM) (1) is installed toward the inside of the engine into the timing advance actuator housing. The timing solenoid (BTM) is spring loaded toward the retarded position. The timing solenoid (BTM) must receive a positive voltage from the ECM in order to move the servo valve spool that changes the fuel injection timing. The lever of Timing Solenoid (BTM) (1) is connected to servo valve spool (5) through sleeve (4). The timing advance unit is connected to the fuel injection pump camshaft. Bolts (11) pull rings (6) and (12) together in order to hold gear (7). Carrier (8) has two helical splines. The outer splines are in contact with the helical splines of ring (6) and the inner splines are in contact with the helical splines on fuel injection pump camshaft (9). When the engine is started, gear (7) drives fuel injection pump camshaft (9) through ring (6) and carrier (8). Advance Timing
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Oil Pressure Locations Toward Maximum Timing Advance (A) Pressure oil (B) Drain oil (1) Timing solenoid (4) Sleeve (5) Valve spool (6) Ring (7) Gear (8) Carrier (9) Fuel injection pump camshaft (10) Body assembly (11) Bolt (12) RingAs the engine begins to run, the ECM sends current to the timing solenoid (BTM) which moves valve spool (4) to the left in the above illustration. At this point, the valve spool (4) closes