821805 2 Mercury LINK-REVERSE LOCK

Illustration 1 g00942307
Schematic of the electronic ignition system and related components (1) Engine mounted junction box (2) Engine speed/timing sensor (3) Manifold air pressure sensor (4) Detonation sensor (5) EIS control module (6) Cat ET (7) DDT (8) Ignition transformer (9) Spark plugEIS control module (5) is mounted on the engine. The EIS control module must be programmed for the installation in order to properly control the ignition. Cat ET (6) or DDT (7) are used to program the EIS control module. The DDT can be connected to junction box (1) .Note: For information on the programmable parameters, refer to Systems Operation, "Electronic Control System Parameters".Two switches have an effect on the ignition system: the engine control switch and the switch for fuel selection.When the engine control switch is switched to the manual start position, the EIS control module begins operating the ignition system.If the switch for fuel selection is in the natural gas position, the EIS control module will use the desired timing that is programmed. If the switch for fuel selection is in the propane position, the EIS control module retards the timing by ten degrees.The EIS control module uses engine speed/timing sensor (2), manifold air pressure sensor (3), and detonation sensors (4) to monitor engine operation.Information from the EIS control module is sent to engine mounted junction box (2). If a problem with the electronic ignition system is detected, a diagnostic code is generated. The diagnostic code can be monitored withCat ET or with the DDT.The EIS control module has several internal components that perform different functions. The components and the functions are listed in Table 1.
Table 1
Internal Components and Functions of the EIS Control Module    
Component     Function    
Ignition control     Receive input from these components:
Engine control switch
Switch for fuel selection
Cat ET
DDT    
Provide information on engine status and diagnostics to electronic service tools.
Provide desired timing and voltage to the ignition transformers' control.
Receive input from the interpreters and the filter.
Ignition transformers' control     Receive input from the ignition control.    
Provide voltage to the transformers.
Provide input to the interpreter of diagnostics for the transformers.
Interpreter of diagnostics for the transformers     Receive input from the ignition transformers' control.    
Provide input to the ignition control.
Interpreter for the signal from the engine speed/timing sensor     Receive input from the engine speed/timing sensor.    
Provide input to the ignition control.
Interpreter for the signal from the manifold air pressure sensor     Receive input from the manifold air pressure sensor.    
Provide input to the ignition control.
Filter for the detonation sensors     Receive input from the detonation sensors.    
Provide input to the ignition control. The relationships of the EIS control module, the sensors, and the transformers are described below.Engine Speed/Timing Sensor
The engine speed/timing sensor provides information about engine speed and the position of the crankshaft to the EIS control module.
Illustration 2 g00818359
(1) Engine speed/timing sensorA timing wheel is mounted in front of the governor drive. Engine speed/timing sensor (1) is installed in the cover. A magnetic pickup is located in the plastic sliphead of the sensor. The EIS control module supplies approximately 13 VDC to the sensor. As the teeth of the timing wheel rotate past the sliphead of the sensor, the sensor generates a signal that matches the pattern of the teeth. The signal is sent to an interpreter for the EIS control module.
Illustration 3 g00807464
Engine speed/timing sensor and timing wheelThe timing wheel has a special tooth pattern that indicates the position of the camshaft and the direction of rotation. The timing wheel has 24 slots in the outer diameter. Twenty-one of the slots are narrow. Three of the slots are about 2.5 times wider than the rest of the slots. When the engine rotates in the normal direction, the slots pass the engine speed/timing sensor in the following order:
1 wide slot
3 narrow slots
2 wide slots
18 narrow slotsThe number one cylinder is at the top center position when the edge of the first narrow slot passes the center of the sliphead. All 24 teeth pass the sliphead during one revolution of the camshaft or two revolutions of the crankshaft.With information from the engine speed/timing sensor, the EIS control module is able to calculate the positions of the pistons in the cylinders. According to the ignition timing that is selected, the EIS control module sends voltage pulses to the transformers for firing of the spark plugs.The engine speed/timing sensor also monitors engine speed. If a speed sensitive timing map is selected, the EIS control module adjusts the ignition timing according to the engine rpm.The EIS control module will shut down the engine if problems with the engine speed/timing sensor's electrical circuit are detected. The corresponding diagnostic code is generated.Manifold Air Pressure Sensor
Illustration 4 g00818361
Manifold air pressure sensorThe EIS control module supplies approximately 13 VDC to the manifold air pressure sensor. The sensor monitors the absolute inlet manifold air pressure. The sensor sends a signal to the EIS control module. The EIS control module has an interpreter that uses the signal to calculate the engine load. If a timing map that is sensitive to load is selected, the EIS control module adjusts the ignition timing according to the calculated load.The EIS control module will generate a diagnostic code if problems with the manifold air pressure sensor's electrical circuit are detected.Detonation Sensors
Two different types of detonation sensors are available. One type is a sensor assembly. The other type consists of two parts: buffer module and accelerometer.