3208 TRUCK ENGINE Caterpillar


Systems Operation

Usage:



General Information


LOW EMISSION SYSTEM COMPONENTS
1. Electronic control. 2. Breather. 3. Inlet manifold. 4. Exhaust tube. 5. Switch cover.


LOW EMISSION SYSTEM COMPONENTS
4. Exhaust tube. 6. Pressure oil line. 7. Solenoid (two). 8. Lever. 9. Actuator rod. 10. Actuator. 11. Oil drain line. 12. Exhaust recirculation valve.

The Low Emission 3208 Engine is a 3208 Engine with modifications to meet California diesel exhaust emissions standards.

The fuel injection pump for the Low Emission Engine has a different load stop pin with a switch and switch cover (5) installed over it. There is a separate electronic control (1) fastened to the fuel injection pump and connected to switch cover (5). Exhaust recirculation valve (12) is installed on the left side exhaust manifold and is operated by actuator (10) and two solenoids (7). Exhaust recirculation tube (4) is installed between exhaust recirculation valve (12) and inlet manifold (3). The Low Emission Engine has a 3° automatic timing advance in place of the standard 5° automatic timing advance unit. Crankcase breather (2) is installed on the valve cover in the place of a positive crankcase ventilation valve.

When the Low Emission Engine is at idle or low load, some of the exhaust is sent back to the inlet manifold. As the engine load increases, the amount of exhaust sent back to the inlet manifold decreases. At full load there is no exhaust sent back to the inlet manifold.

The switch and switch cover (5), and electronic control (1) operate two solenoids (7) and actuator (10). The actuator uses engine oil pressure that works against pistons in the actuator to control the position of actuator rod (9). The actuator rod is connected to lever (8) on the shaft of exhaust recirculation valve (12). Baffles on the valve shaft control the amount of exhaust gas that is sent back to the inlet manifold to be burned again.

The Low Emission System is designed so that if the electronic control does not function properly, there will be NO exhaust sent to the inlet manifold.


NOTICE

DO NOT use a 24 V source to "Jump Start" a Low Emission Engine. The electronic control will be damaged if more than 12 V is connected to the electrical system.


Low Emission Systems

Switch And Switch Cover And Electronic Control


LOW EMISSION SWITCH AND SWITCH COVER
1. Switch cover. 2. Wires (to electronic control). 3. Fuel setting adjustment screw. 4. Switch. 5. Load stop pin. X. Contact. Y. Contact. Z. Full load contact.

Switch (4) opens or closes electrical circuits which control the operation of the two actuator solenoids. The circuits are completed when load stop pin (5) makes contact with one or both contacts (X or Y). Contacts (X and Y) can be adjusted to a specific distance apart so that contact (X) is closed by the load stop pin before contact (Y) is closed. Contacts (X and Y) must also be adjusted a specific distance from fuel setting screw (3). Contact (Z) is for the use of a circuit tester when the fuel setting is adjusted.

Only a very small amount of electrical current flows through the contacts in switch (4). This current goes through the contacts in switch cover (1). This current goes through the contacts in the switch cover and through wires (2) to electronic control (7). The small electrical current turns transistors in the electronic control on or off. The transistors switch the larger current to the actuator solenoids.

At idle and low loads, load stop pin (5) will not close contacts (X or Y) and only the upper solenoid is activated. At medium load, load stop pin (5) closes contact (X), and both upper and lower solenoids are activated. At high load, load stop pin (5) closes both contacts (X and Y) and only the lower solenoid is activated.


LOW EMISSION ENGINE CONTROLS
1. Switch cover. 6. Wire connector to solenoids. 7. Electronic control.

Actuator And Solenoids


ACTUATOR WITH ENGINE AT IDLE OR LOW LOAD
1. Upper solenoid. 2. Rod. 3. Piston. 4. Spring. 5. Lower solenoid. 6. Stop. 7. Piston

When the engine is at idle or low load, upper solenoid (1) is activated and lower solenoid (5) is not activated. When upper solenoid (1) is activated, it sends pressure oil to the top of piston (3). Spring (4) is put in compression until the bottom of piston (3) is against the top of piston (7). Piston (7) is pushed down and rod (2) moves back into actuator body until the valve is closed. With the engine at idle or low load, the maximum amount of exhaust is sent to the inlet manifold.


ACTUATOR WITH ENGINE AT MEDIUM LOAD
1. Upper solenoid. 2. Rod. 3. Piston. 4. Spring. 5. Lower solenoid. 6. Stop. 7. Piston.

When the engine is at medium load, solenoids (1) and (5) are activated. Lower solenoid (5) sends pressure oil to the bottom of piston (7). Upper solenoid (1) sends pressure oil to the top of piston (3). Piston (7) is pushed up against stop (6). Piston (3) and rod (2) are pushed down. Spring (4) is put in compression until the bottom of piston (3) is against the top of piston (7). Piston (7) is held up against stop (6) because bottom of piston (7) has more area and gets more force. With the engine at medium load, rod (2) is moved part of the way out of the actuator body and the valve is opened part of the way.


ACTUATOR WITH ENGINE AT HIGH LOAD
1. Upper solenold. 2. Rod. 3. Piston. 4. Spring. 5. Lower solenoid. 6. Stop. 7. Piston.

When engine is at high load, lower solenoid (5) is activated and upper solenoid (1) is not activated. When lower solenoid (5) is activated, it sends pressure oil to the bottom of piston (7). Piston (7) is pushed up against stop (6). Spring (4) pushes piston (3) and rod (2) to the top of the actuator body. With the engine at high load, rod (2) is moved the farthest distance out of the actuator body. The valve is opened all the way and no exhaust is sent to the inlet manifold.

If there is a failure to the switch, switch cover, or electronic control, both upper and lower solenoids will close. With no oil pressure to the actuator, spring (4) will move piston (3) and rod (2) all the way out of the actuator and open the valve all of the way. There will be no exhaust sent to the inlet manifold.

Valve


Positions Of Valve

Valve (2) is fastened to the output of exhaust manifold (1) on the left hand side of the engine. It has two plates fastened to shaft (6) which control the flow of the exhaust gas. Shaft (6) is fastened by lever (5), link, and rod end to output rod (4) of actuator (7).

When the engine is at idle or low load, output rod (4) of the actuator (7) moves into the body of actuator (7). It pulls lever (5) and turns shaft (6) in valve (2). This causes the large plate to close in valve (2) to exhaust (8). It causes the small plate to open in valve (2) to tube (3). Tube (3) goes to the air inlet manifold. The maximum amount of exhaust gas goes through tube (3) to the air inlet manifold.


ACTUATOR AND VALVE
1. Exhaust manifold. 2. Valve. 3. Tube. 4. Rod. 5. Lever. 6. Shaft. 7. Actuator. 8. Outlet to the exhaust.

When the engine is at medium load, output rod (4) of actuator (7) moves part of the way out of the body of actuator (7). This pushes on lever (5) and turns shaft (6) in valve (2). It causes the large plate to open some of valve (2) to the exhaust (8). It causes the small plate to close some of valve (2) to tube (3). Part of the exhaust gas goes through valve (2) to exhaust (8) and the remainder of the exhaust gas goes through valve (2) to tube (3) to the air inlet manifold. A smaller amount of exhaust is sent to the air inlet manifold.

When the engine is at full load, output rod (4) of actuator (7) moves more out of the body of actuator (7). This pushes more on lever (5) and turns shaft (6) in valve (2). It causes the large plate to open in valve (2) to exhaust (8). It causes the small plate to close in valve (2) to tube (3). All of the exhaust gas goes through valve (2) to exhaust (8). No exhaust goes to the air inlet manifold.

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