3208 TRUCK ENGINE Caterpillar


Systems Operation

Usage:



General Information


3208 ENGINE WITH EXHAUST GAS RECIRCULATION (EGR)
1. EGR switch. 2. Fumes disposal tube. 3. Breather. 4. Air inlet manifold. 5. Cover for EGR actuator. 6. EGR valve. 7. EGR tube.

The Low Emission 3208 Engine with Exhaust Gas Recirculation (EGR) is a 3208 Engine with modifications to meet low emissions standards.

When an engine is first started and until it reaches the normal temperature for operation, there is an incomplete (not complete) burning of the fuel. This results in a large amount of smoke. In Exhaust Gas Recirculation (EGR), some of the exhaust gas is sent back to the inlet manifold to be burned again. At low load there is maximum EGR. As the engine load is increased, the amount of EGR becomes less. At full load, there is no EGR.

The fuel injection pump of the 3208 Engine with EGR has a different load stop pin with an EGR switch and cover assembly installed on it. The load stop pin will open or close an electrical circuit in the switch and cover assembly. This switch controls the operation of two solenoids. The solenoids control the flow of pressure oil through two lines from the oil cooler to the EGR actuator. There is a drain line from the actuator to the oil pan. The pressure oil to the actuator works against pistons in the actuator to control the position of a rod in the actuator.


EXHAUST GAS RECIRCULATION (EGR) ACTUATOR AND VALVE
6. EGR valve. 7. EGR tube. 8. Shaft. 9. Pressure oil lines (two). 10. Lever. 11. Rod. 12. EGR actuator. 13. Solenoids (two). 14. Oil drain line.

The EGR valve is installed on the exhaust manifold. The rod from the actuator works through a link and lever on the shaft of the EGR valve. The shaft works a baffle type mechanism which controls how much exhaust gas goes out through the exhaust and how much goes to the air inlet manifold. When EGR takes place, some of the air in the inlet manifold is replaced by exhaust gas.

The 3208 Engine with EGR does not use a PCV valve. It has a breather on the valve cover. The 3208 Engine with EGR has a 3° automatic timing advance.

The design of the EGR system is made so that if there are any problems with it, full EGR will be in effect. With full EGR in effect, the engine will not make full power. There will be more smoke. If it is necessary, the engine can be run with full EGR in effect. If the engine is run when there is a problem (malfunction) with the EGR system, be sure to drain the oil from the engine after the problem (malfunction) has been corrected. Install new oil filters and put new oil in the engine.

EGR Systems

EGR Switch And Cover Assembly


EGR SWITCH AND COVER ASSEMBLY
1. EGR switch cover. 2. Fuel setting screw. 3. Wire. 4. Bullet connector. 5. Female contact. 6. Male contact. 7. Fuse holder. 8. Fuse. 9. EGR switch. 10. Load stop pin. 11. Wire. 12. Spade terminal. X. EGR contact. Y. EGR contact. Z. Full load ground contact.

The EGR switch will open or close circuits which control the operation of two solenoids. The circuits are controlled when load stop pin (10) makes contact with one or both contacts (X) or (Y) in the EGR switch (9). Contacts (X) and (Y) can be adjusted to a specific distance apart so that contact (X) is closed by load stop pin (10) before contact (Y) is closed. Contacts (X) and (Y) must also be adjusted a specific distance from fuel setting screw (2). Contact (Z) is a ground for the fuel setting adjustment.

EGR switch cover (1) is installed over EGR switch (9). EGR switch cover (1) has electronic components which are controlled by the mechanical contacts made in EGR switch (9). Wire (11) of EGR switch cover (1) connects to shut-off solenoid (13) and is the source of electricity. Fuse holder (7) in wire (11) has a four ampere ceramic special fast blow TYPE GBB fuse (8). Wire (3) ends in a bullet connector (4) which has male contact (6) and female contact (5).

At low load when load stop pin (10) has not closed contact (X) or (Y), a supply of electricity is made through female contact (5) to activate the lower solenoid. At medium load when load stop pin (10) closes contact (X), a supply of electricity is made through male contact (6) and female contact (5) to activate the lower and upper solenoids. At greater load when load stop pin (10) closes contact (X) and (Y), a supply of electricity is made through male contact (6) to activate the upper solenoid. At full load when load stop pin (10) closes contacts (X), (Y) and (Z), a supply of electricity is made through male contact (6) to activate the upper solenoid.


EGR SWITCH COVER
1. EGR switch cover. 3. Wire. 4. Bullet connector. 7. Fuse holder. 11. Wire. 13. Shut-off solenoid.

EGR Actuator And Solenoids


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

When engine is at low 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 low load, rod (2) is moved the farthest distance from the actuator body. This causes the most EGR.


EGR 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 back into the actuator body and less EGR takes place.


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

When the engine is at full 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 EGR valve is closed. With the engine at full load, no EGR takes place.

EGR Value


POSITIONS OF EGR VALVE

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

When the engine is at low load, the output rod (4) of the EGR, actuator (7) moves out of the body of EGR actuator (7). It pushes lever (5) and turns shaft (6) in EGR valve (2). This causes the large plate to close EGR valve (2) to the exhaust. It causes the small plate to open EGR valve (2) to EGR tube (3). EGR tube (3) goes to the air inlet manifold. Most of the exhaust gas goes through EGR tube (3) to the air inlet manifold. Maximum EGR takes place.


EGR ACTUATOR AND VALVE
1. Exhaust manifold. 2. EGR valve. 3. EGR tube. 4. Rod. 5. Lever. 6. Shaft. 7. EGR actuator. 8. Outlet to the exhaust.

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

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

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