DIESEL EGR SYSTEM DIAGNOSIS SERVICE MANUAL UPDATE

THE FOLLOWING IS A DESCRIPTION OF THE 1982 4.3L V6 DIESEL EGR SYSTEM. THIS REPLACES THE DESCRIPTION ON PAGE 6E1-68 OF THE 1982 OMEGA AND CUTLASS CIERA SERVICE MANUAL. VACUUM FROM THE VACUUM PUMP IS REGULATED BY THE VACUUM REGULATOR VALVE (VRV) MOUNTED ON THE INJECTION PUMP. VACUUM IS HIGHEST AT IDLE AND DECREASES TO ZERO AT WIDE-OPEN THROTTLE. THE EGR VALVE IS FULLY OPEN AT IDLE. AN EXHAUST PRESSURE REGULATOR (EPR) VALVE IS USED IN THE EXHAUST SYSTEM TO INCREASE BACKPRESSURE IN THE EXHAUST FLOW. THIS WILL INCREASE THE AMOUNT OF EXHAUST GAS AVAILABLE TO FLOW THROUGH THE INTAKE MANIFOLD, EGR VALVE AND AIR CROSSOVER. AT IDLE, THE EGR VALVE IS FULLY OPEN AND THE EPR VALVE IS FULLY CLOSED. AS THE THROTTLE IS OPENED, VACUUM DECREASES. AT WIDE-OPEN THROTTLE, THE EGR VALVE IS FULLY CLOSED AND THE EPR VALVE IS FULLY OPEN. VACUUM REQUIRED TO OPERATE THE EGR AND EPR VALVES IS FURTHER MODULATED BY A VACUUM LIMITING VACUUM MODULATING VALVE (VLVMV) AND A TORQUE CONVERTER CLUTCH TRIM VACUUM MODULATOR VALVE (TCCTVMV). THE VLVMV ALLOWS UP TO 40.5 KPA (12" HG.) OF VACUUM TO THE EGR AND EPR VALVES WHEN THE TORQUE CONVERTER CLUTCH IS DISENGAGED. THE TCCTVMV IS USED TO LIMIT THE VACUUM TO THE EGR AND EPR VALVES TO A MAXIMUM OF 28.7 KPA (8 1/2" HG.) WHEN THE TORQUE CONVERTER CLUTCH IS ENGAGED.

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