20586 Mercruiser NUT, ROCKER COVER CHIMENY STUD

Table 1
Temperatures that are Necessary for Activation of the Air Inlet Heater Prior to Engine Cranking (30 Second Preheat Cycle)
Elevation of the Application Sum of Temperatures
Less than 1675 m (5500 ft) 25° C (77° F)
Greater than 1675 m (5500 ft) 53° C (127° F) If the sum of the temperatures is below the temperature that is mentioned in Table 1, the air inlet heater will be activated for a maximum of 30 seconds during the preheat cycle.If the operator attempts to start the engine prior to the completion of preheat, the ECM reverts to the mode of engine cranking.Mode of Engine CrankingDuring engine cranking, the ECM first checks if the coolant temperature is less than 0 °C (32 °F). If this condition is true, the ECM activates the heater during engine cranking.If the preceding condition is false, the ECM calculates the sum of the coolant temperature plus the intake manifold air temperature. This sum must be below the following temperature in order for the air inlet heater to be activated during engine cranking:
Table 2
Temperatures that are Necessary for Activation of the Air Inlet Heater During Engine Cranking
Elevation of the Application Sum of Temperatures
Less than 1675 m (5500 ft) 25° C (77° F)
Greater than 1675 m (5500 ft) 63° C (145° F) If either of the preceding conditions are true, the ECM will activate the heater until the engine starter is disengaged. If the engine fails to start, the ECM reverts to the mode of powerup and preheat. If the engine starts the ECM proceeds to the mode of engine started.Mode of Engine StartedAfter the engine has started, the same combination of intake manifold air temperature and coolant temperature will determine the state of the heater. The cycle has two strategies:
Continuous operation
Intermittent operationContinuous OperationDuring continuous operation of the air inlet heater, the heater may operate continuously for a maximum of seven minutes after the engine has started. The ECM will exit the mode of continuous operation early if the sum of the coolant temperature plus the intake manifold air temperature exceeds the following temperatures:
Table 3
Temperatures that are Necessary for an Early Exit from Continuous Operation of the Air Inlet Heater
Elevation of the Application Sum of Temperatures
Less than 1675 m (5500 ft) 35° C (95° F)
Greater than 1675 m (5500 ft) 63° C (145° F) When this temperature is exceeded the air inlet heater is turned off and the mode of engine started is completed.If the temperatures for the preceding strategy are not met in seven minutes, the strategy for intermittent operation will be performed.Intermittent OperationDuring the strategy for intermittent operation, the ECM cycles the power to the air inlet heater in ten second intervals.This strategy will be effective for a maximum of 13 minutes after the strategy has begun. The ECM will exit the mode of intermittent operation early if the sum of the coolant temperature plus the intake manifold air temperature exceeds the following temperatures:
Table 4
Temperatures that are Necessary for an Early Exit from Intermittent Operation of the Air Inlet Heater
Elevation of the Application Sum of Temperatures
Less than 1675 m (5500 ft) 35° C (95° F)
Greater than 1675 m (5500 ft) 63° C (145° F) When this temperature is exceeded, the ECM shuts off the air inlet heater until the keyswitch is cycled.If there is an active diagnostic code for the coolant temperature sensor or the intake manifold air temperature sensor, the following strategy will be used:Coolant Temperature SensorIf there is an active diagnostic code for the coolant temperature sensor, all temperature conditions will rely solely on the air inlet temperature sensor. All temperature conditions will be satisfied at an air inlet temperature of 10 °C (50 °F) at all altitudes.Air inlet Temperature SensorIf there is an active diagnostic code for the air inlet temperature sensor, all temperature conditions will rely solely on the coolant temperature sensor. All temperature conditions will be satisfied at a coolant temperature of 40 °C (104 °F) at all altitudes.
Illustration 1 g01351393
Schematic for the air inlet heater
Test Step 1. Inspect the Electrical Connectors and the Wiring
Turn the keyswitch to the OFF position.
Illustration 2 g01351533
Location of the components that are related to the air inlet heater (typical left side engine view)
(1) Air inlet heater relay
(2) Air inlet heater
(3) J2/P2 ECM connectors
Thoroughly inspect all of the connections for relay (1) and for heater element (2). Also, thoroughly inspect ECM connectors (3). Refer to Troubleshooting, "Electrical Connectors - Inspect" for details.
Illustration 3 g01351538
(P2-9) Return for the air inlet heater
(P2-12) Air inlet heater