PINION 7V9961 - Caterpillar

A 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.
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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
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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
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Detonation sensor's buffer module
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(1) Buffer module (2) AccelerometerA detonation sensor consists of buffer module (1), accelerometer (2), and wiring. A detonation sensor is located on the upper cylinder block on each side of the engine. Each sensor monitors one bank of cylinders. The EIS control module supplies approximately 13 VDC to the sensors.The detonation sensors provide an electrical signal of the mechanical engine vibrations to the EIS control module. The accelerometers provide electrical signals to the buffer modules. The buffers provide a signal with an offset of approximately 6 VDC to a filter