Ignition System - Service Information: Overview Jeep Compass I рестайлинг 2

DESCRIPTION

Note. All engines use a fixed ignition timing system. Basic ignition timing is not adjustable. All spark advance is determined by the Powertrain Control Module (PCM).

The ignition system used on these engines is referred to as coil on plug. The system's four main components are the coils, crankshaft position sensor, spark plugs, and camshaft position sensors. The coil on plug ignition system utilizes an ignition coil for every cylinder. The ignition coils are mounted directly over the each spark plug.

OPERATION

The crankshaft position sensor and camshaft position sensor are hall effect devices. The camshaft position sensor and crankshaft position sensor generate square wave pulses that are inputs to the PCM. The PCM determines engine position from these sensors. The PCM calculates injector sequence and ignition timing from crankshaft AND camshaft position.

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The firing order is 1-3-4-2.

There is a glow plug control module and a glow plug relay control that use information received from engine control module.

When the ignition (key) switch is placed in the ON position, a signal is sent to the ECM relating current engine coolant temperature. This signal is sent from the engine coolant temperature sensor.

The glow plug control module receives information about the glow function from the engine control module. The start of glow plug operation, the period of glow plug operation, the actuation frequency and the pulse duty factor are therefore determined by the engine control module.

The glow plugs are used to preheat the combustion chambers in order to achieve the ignition temperature required for the fuel-air mixture.

The heating element is integrated in the glow rod. It consists of a heating winding and a control winding connected in series.

The glow plug system is a quick start type. This allows for immediate start in practically all weather conditions without long periods of preglowing. This works in conjunction with 6-hole injectors, which have a special "ignition" spray pattern. The glow plugs reach 1000° C (1832° F) in 2 seconds.

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1. Release quarter turn lock tabs (1) and remove air inlet duct (2).
2. Disconnect the negative battery cable.
3. Remove engine cover.
4. Disconnect the fuel rail pressure sensor harness connector (2).
5. Release the four lock tabs (1) position aside engine wire harness (2).
6. Disconnect the glow plug four way wire harness connector.
7. Disconnect glow plug wire harness connector (1). NOTE: Clean the area around the glow plug of dirt and debris before removing.
8. Remove glow plugs (1) from cylinder head.

The camshaft position sensors are mounted to the front and rear of the cylinder head.

CAMSHAFT POSITION SENSOR-BANK 1 SENSOR 1 is mounted to the forward face of the cylinder head and reads the intake camshaft signals.

CAMSHAFT POSITION SENSOR-BANK 1 SENSOR 2 is mounted to the rear face of the cylinder head and reads the exhaust camshaft signals.

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Note. The graphic represents the relationship between camshaft and crankshaft sensors edges with camshafts in "lock pin" position (cam shafts are not "phasing"). This is normally seen during idle.

Depiction of good camshaft and crankshaft square wave signals for 4 cylinder engines.

The PCM sends approximately 5 volts to the Hall-effect sensor. This voltage is required to operate the Hall-effect chip and the electronics inside the sensor. The input to the PCM occurs on a 5 volt output reference circuit. A ground for the sensor is provided through the sensor return circuit. The PCM identifies camshaft position by registering the change from 5 to 0 volts, as signaled from the camshaft position sensor.

The PCM determines fuel injection synchronization and cylinder identification from inputs provided by the camshaft position sensor and crankshaft position sensor. From the two inputs, the PCM determines crankshaft position.

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1. Remove the air cleaner hose to throttle body, disconnect the inlet air temperature sensor electrical connector.
2. Disconnect negative battery cable.
3. Disconnect electrical connector from camshaft position sensor.
4. Remove camshaft position sensor mounting screws.
5. Remove sensor.

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1. Disconnect negative battery cable.
2. Disconnect electrical connector at sensor.
3. Remove nut retaining heat shield.
4. Pull heat shield out to uncover sensor.
5. Remove mounting bolt.
6. Remove sensor.

The knock sensor is bolted to the cylinder block. The knock sensor is designed to detect engine vibration that is caused by detonation or preignition.

When the knock sensor detects a knock in one of the cylinders, it sends an input signal to the PCM. In response, the PCM retards ignition timing for all cylinders by a scheduled amount.

Knock sensors contain a piezoelectric material which constantly vibrates and sends an input voltage (signal) to the PCM while the engine operates. As the intensity of the crystal's vibration increases, the knock sensor output voltage also increases.

The voltage signal produced by the knock sensor increases with the amplitude of vibration. The PCM receives as an input the knock sensor voltage signal. If the signal rises above a predetermined level, the PCM will store that value in memory and retard ignition timing to reduce engine knock. If the knock sensor voltage exceeds a preset value, the PCM retards ignition timing for all cylinders. It is not a selective cylinder retard.

The PCM ignores knock sensor input during engine idle conditions. Once the engine speed exceeds a specified value, ignition timing retard is allowed.

Ignition timing is retarded uses its own short term and long term memory program.

Long term memory stores previous detonation information in its battery-backed RAM. The maximum authority that long term memory has over timing retard can be calibrated.

Short term memory is allowed to retard ignition timing up to a preset amount under all operating conditions (as long as RPM is above the minimum RPM) except WOT. The PCM, using short term memory, can respond quickly to retard timing when engine knock is detected. Short term memory is lost any time the ignition key is turned off.

Note. Over or under tightening affects knock sensor performance, possibly causing improper spark control.

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The knock sensor bolts into the side of the cylinder block in front of the starter under the intake manifold.

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1. Disconnect the negative battery cable.
2. Remove the bolt holding the knock sensor.
3. Remove sensor with electrical connector attached.
4. Disconnect electrical connector from knock sensor.
5. Remove the knock sensor.

There is both an Intake and an exhaust camshaft sensor on vehicles equipped with a World Engine. The variable valve timing system used on World Engines requires the exact position of both the intake and exhaust camshaft. The GPEC1 uses camshaft sensor data along with crankshaft data to determine the actual position of the camshafts. Intake and exhaust phaser oil control valves are required on World Engine vehicles using variable valve timing. The oil valves direct oil to the Intake and exhaust phasers. Oil pressure in the phasers moves the camshafts to an advanced or retarded position.

To resolve this inherent conflict between optimum high and low speed valve timing, the GPEC1 controlled engine uses a variable valve timing system. The variable valve timing system advances and retards valve timing by rotating the position of both the intake and exhaust camshafts. With this system, the intake valve opening can range from 80 to 120 crankshaft degrees after Top Dead Center. Likewise, the exhaust valve opening can range from 85 to 120 crankshaft degrees before Top Dead Center. This degree of flexibility provides many benefits, including: Improved Engine Performance, Increased Fuel Economy, Improved Idle Stability and Decreased Engine Emissions. In non operating condition, the camshaft stays in lockpin position of cam phases. This is 120 degrees ATDC for intake camshaft and 120 degrees BTDC for exhaust camshaft.

The variable valve timing system is electronically controlled and hydraulically operated. The GPEC1 receives information from many sensors to determine the optimum valve timing. It then pulse-width modulates oil control valves which direct oil to the cam phasers. The cam phasers use oil pressure to rotate the intake and exhaust camshafts. The rotation of the camshafts is referred to as cam phasing. Before the GPEC1 can begin commanding the camshaft phasing, several enabling conditions must be met

1. The engine oil temperature must be at least -6.6°C (20°F)
2. The oil control valve coil temperature must be less than 140°C (284°F)
3. Engine speed must be at least 600 to 1000 RPM to achieve minimum oil pressure.
4. Battery voltage must be at least 10 volts
5. And there must be no camshaft or crankshaft sensor faults, engine timing faults, or oil control valve faults

First we will examine variable valve timing enabling conditions, and then we will take a closer look at the inputs and outputs of the system

1. Accelerator pedal position sensor
2. Oil temperature sensor
3. Map sensor
4. Intake cam sensor
5. Exhaust cam sensor
6. Crankshaft sensor
7. GPEC1
8. Exhaust phaser oil control valve
9. Intake phaser oil control valve
10. Inputs
11. Engine control module
12. Outputs
13. Sensed battery voltage

A minimum oil temperature is required to enable variable valve timing operation. Oil temperature and viscosity also have an impact on the operation of variable valve timing after start-up. Oil is used to control the movement of the camshafts. An incorrect oil viscosity could adversely affect the operation of the system or even render the system inoperative. It may even set a fault code.

The accelerator pedal position sensor indicates how far the driver wants to open the throttle plate. The GPEC1 calculates an initial camshaft set point based on whether the accelerator pedal is at part throttle or wide open throttle.

The MAP sensor provides information regarding engine load.

Sensed battery voltage provides information regarding current system voltage. Sensed battery voltage must be at least 10 volts in order for the oil control valves to function properly.

This information allows the GPEC1 to adjust camshaft timing to achieve the best fuel economy, the best engine performance or a combination of both. The hall-effect crankshaft sensor provides RPM information and determines when the number one piston is approaching Top Dead Center. The sensor generates a signal as the tone wheel, attached to the crankshaft, rotates. The tone wheel has 60 teeth minus two. When the gap, created by the missing teeth passes by the sensor, a signal is produced that indicates the number one piston is at Top Dead Center. The GPEC1 uses crankshaft sensor data along with camshaft data to determine the actual position of the camshaft. There are two hall-effect camshaft sensors on engines equipped with variable valve timing. The GPEC1 uses camshaft sensor data along with crankshaft data to determine the actual position of the camshaft.

The GPEC1 individually controls each valve. It sends a pulse width modulated signal to move a spool within the outer casing of the valve. Depending upon spool movement, oil is directed through the passages to advance or retard cam timing. The oil control valve also has a special cleaning strategy at key-on. The cleaning strategy is known as "debris crush mode". At key-on the GPEC1 cycles the oil control valve on and off several (5) times to crush any debris in the oil control valve and prevent the spool valve from sticking. In non operating condition, the camshaft stays in lockpin position of cam phases. This is 120 degrees ATDC for intake camshaft and 120 degrees BTDC for exhaust camshaft.

Note. The debris crush mode will only occur with the key on and the engine off (KOEO). If the ignition is cycled to the start position without a momentary pause (immediate crank), the debris crush mode will not occur. In this instance the procedure will be performed at the next key off cycle.

There are two oil control valves. One valve directs oil to the intake cam phaser, the other valve directs oil to the exhaust cam phaser. The valves are designed and function in the same manner. The outer casing of each oil valve has five oil passages. A passage for pressurized supply oil. A passage to the advance chamber of the cam phaser. A passage to the retard chamber of the cam phaser. A passage for oil return from the advance chamber of the cam phaser. A passage for oil return from the retard chamber of the cam phaser. Oil flows through the passages and applies pressure to the cam phasers to change cam timing.

There are two cam phasers. One phaser controls the position of the intake camshaft. The other phaser controls the position of the exhaust camshaft. The phasers consist of a sprocket, a rotor vane, and a housing or stator. The exhaust cam phaser also consists of a front bushing and spring. We will discuss the purpose and function of the bushing and spring later. The housing is bolted and permanently fixed to the camshaft sprocket, while the rotor vane is bolted and permanently fixed to the camshaft. With this design, any movement of the rotor vane in relation to the housing will also move the camshaft. The phaser and sprocket are serviced as an assembly.

Camshaft and crankshaft sensors provide feedback to the GPEC1 regarding the actual position of the camshafts. The GPEC1 then compares the actual camshaft positioning with desired positioning. If the desired positioning is not achieved within a specified time, during the second key cycle a trouble code is set.

There are six new diagnostic trouble codes available to help you determine if the control circuit from the GPEC1 to the oil control valve is intact and operating properly. The codes identify whether the control circuit is open, shorted to ground, or shorted to power. Three trouble codes are related to intake camshaft positioning, the other three codes are specific to exhaust camshaft positioning.

The oil control valve contains both electrical and mechanical components. It is electrically controlled by the GPEC1. The electrical current that energizes the coil results in mechanical motion of the spool valve. It is possible to verify both the electrical and mechanical operation of the valve. The oil control valve consists of a coil that is energized to move a spool within an outer casing. The condition of the coil can be tested with a Digital Volt Ohmmeter or DVOM. With the DVOM set to measure resistance, check the coil for an open, a short to ground, or excessive resistance. The correct resistance value of the coil is between 6 and 8 ohms. The mechanical operation of the oil control valve can be tested using actuator commands on the scan tool. Remove the oil control valve, then navigate to the actuator menu and select the oil control valve. Use commands to activate the valve and watch as the spool valve moves back and forth inside the casing.

Because the cam phasers are hydraulically operated by engine oil, the condition of the oil is very important. The oil must be of the correct viscosity, not obstructed by debris, to maintain correct pressure. Maintaining the correct oil viscosity is critical to the operation of the variable valve timing system. The wrong oil viscosity may cause the variable valve timing to malfunction and trouble codes to set. The correct oil viscosity for this system is 5W20. Oil must be clean, unobstructed and free to flow through the variable valve timing system. Oil could become obstructed in oil passages located in the cylinder head, cylinder block, or even in the oil screen. In the event oil flow is obstructed, further diagnosis or disassembly may be required to pin point the source of the obstruction. The variable valve timing system relies on oil pressure to advance or retard the position of the camshaft. Insufficient oil pressure will adversely affect the operation of variable valve timing. The minimum oil pressure for this system is 15 psi at normal operating temperature.

Though not directly used to change camshaft positioning, the oil screen is an important component of the variable valve timing system. It helps to remove debris going to the variable valve timing components. The oil screen is located in the cylinder block, immediately below the cylinder head. Oil must pass through the oil screen before entering the oil control valve. The cylinder head must be removed to service the oil screen. The intention is not to service the oil screen during vehicle life.

How the cam phaser works. The cam phaser assembly has eight separate chambers; four advance chambers and four retard chambers. When camshaft advance is requested, oil enters all four advance chambers and exerts force on the rotor vane. Because the rotor vane is bolted to the camshaft, the entire camshaft profile moves along with the rotor vane. At the same time, oil is forced out of the retard chambers. When camshaft retard is requested oil enters the retard chambers to move the camshaft in the opposite direction. There is a lock pin on one side of the rotor vane that fits inside a recessed area in the housing. The lock pin ensures that the default position of the intake cam phaser is 120 crankshaft degrees full retard and the default position of the exhaust cam phaser is 120 crankshaft degrees full advance. When the engine is turned off, rotational force and inertia move the intake camshaft and rotor vane toward the retard position. The exhaust cam phaser includes a spring and bushing to work against the rotational force of the engine, allowing the exhaust cam phaser to lock in the fully advanced position. Under most conditions the cam phasers are returned to lock pin position when the engine is turned off. In the unique condition of an engine stall, which abruptly shuts off the engine, the cam phasers may not return to the lock pin position. In this case, the phasers will return to the lock pin position at the next start-up. Lock pin position is the most ideal cam timing for idle stability. When engine RPM exceeds approximately 600 to 1000 RPM, oil pressure unlocks the pins and variable valve timing resumes. Once enabling conditions are met, the GPEC1 uses input from sensors to calculate optimum valve timing.

There are four preprogrammed modes from which the GPEC1 bases initial valve timing.

1. Starting
2. Idle or Part throttle
3. Wide open throttle
4. Limp-in or Default

From each preprogrammed mode, the GPEC1 adjusts valve timing based on operating conditions.

GPEC1 has calculated optimum intake valve timing of 112 degrees after Top Dead Center and optimum exhaust valve timing of 97 degrees before Top Dead Center. The GPEC1 pulse width modulates the oil control valves to advance or retard the camshaft to their desired location. The spool valve inside the intake oil control valve is energized and moves to allow pressurized oil into the advance chambers of the intake cam phaser. At the same time, the spool valve inside the exhaust oil control valve is energized and moves to allow pressurized oil into the retard chambers of the exhaust cam phaser. Oil enters the advance chambers of the intake phaser and the retard chambers of the exhaust phaser. Oil pressure releases the lock pin from its locked position and pushes against the rotor vane. Both the rotor vanes are moved, advancing the intake camshaft and retarding the exhaust camshaft.

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1. Disconnect negative battery cable.
2. Remove engine cover.
3. Rotate hose clamp out of way.
4. Disconnect oil pressure sensor electrical connector.
5. Remove oil pressure sensor.
6. Disconnect variable valve timing solenoid electrical connector.
7. Remove variable valve timing solenoid mounting bolt.
8. Pull solenoid straight out of cylinder head.

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1. Disconnect negative battery cable.
2. Remove engine cover.
3. Disconnect variable valve timing solenoid electrical connector.
4. Remove variable valve timing solenoid mounting bolt.
5. Pull solenoid straight out of cylinder head.