Engine Controls - Theory & Operation Dodge Spirit I

INTRODUCTION

Note. Monaco and Premier models are manufactured with either an early or late design. Only late design models are covered in this article. Late design models are equipped with DIS, with engine controller (SBEC) located next to battery. Service procedures for early design models, with engine code Z7X711, are the same as those found in 1990 DOMESTIC SERVICE & REPAIR

Note. Shadow and Sundance Convertible models equipped with 2.5L TBI engine are manufactured with either early or late design fuel, ignition and emission systems. Late design vehicles use an epoxy ignition coil, mounted on thermostat housing, and a high pressure fuel system requiring quick-connect fuel fittings. Early design vehicles use an oil-filled ignition coil, mounted on right inner fender, and a low pressure fuel system using hoses and clamps.

This article covers the basic description and operation of engine performance related systems and components. Read this article before working on unfamiliar systems.

TURBO I & III

The turbocharging system is mounted on the manifold side of engine. (Scheme 1) System includes a turbine assembly, center housing rotating assembly, compressor assembly, wastegate, and throttle body. The turbine is spun by exhaust gas causing compressor wheel to draw in air.

Scheme 1

Maximum manifold pressure (boost) is controlled by the wastegate solenoid. Operation of the wastegate is controlled by varying duty cycle of wastegate solenoid. This is accomplished by the Single Board Engine Controller (SBEC).

A barometric read solenoid controls whether manifold pressure or atmospheric pressure is supplied to MAP sensor. Atmospheric pressure is supplied to MAP sensor periodically to measure barometric pressure. The barometric information is used for boost control. The barometric read solenoid is controlled by the SBEC and is located in the MAP sensor vacuum line next to the MAP sensor.

CONTROL UNIT

The Single Board Engine Controller (SBEC) is a digital computer that controls air/fuel ratio, canister purge, charging system, cooling fan, emission control devices, fuel injector pulse width, idle speed, ignition coil dwell, spark advance and turbocharger wastegate .

The SBEC has a voltage converter that converts battery voltage to regulated 5-volt or 8-volt outputs. The regulated 5-volt output is used to power Manifold Absolute Pressure (MAP) sensor, Throttle Position Sensor (TPS) and logic circuits. The regulated 8-volt output is used to power distributor on all engines except models equipped with Direct Ignition System (DIS). On models with DIS, an 8-volt output is used to power camshaft and crankshaft sensors.

INPUT DEVICES

Note. Components are grouped into 2 categories. The first category covers INPUT DEVICES, which control or produce voltage signals that are monitored by the SBEC. The second category covers OUTPUT SIGNALS, which are components controlled by the SBEC.

Vehicles are equipped with different combinations of input devices. Not all devices are used on all models. To determine the input device usage on a specific model, see appropriate wiring diagram in WIRING DIAGRAMS article. The available input signals include the following

A/C CONTROL MODULE (ACM)

When A/C function is selected, the ACM sends a predict signal to the SBEC approximately .5 second before A/C clutch is energized. The SBEC increases engine idle speed to compensate for increased engine load. Approximately .5 second before ACM de-energizes A/C compressor clutch, the ACM stops sending predict signal and SBEC reduces idle speed to compensate for decrease in engine load.

BRAKE SWITCH

The brake switch is mounted on brake pedal support bracket. Brake switch is used as an input to the SBEC during deceleration and full stop conditions. Together with other inputs, brake switch is used to maintain engine idle speed by controlling automatic idle speed motor (AIS) position.

CAMSHAFT ANGLE SENSOR

The cam sensor is mounted on top of timing chain cover. This sensor reads slots in cam timing sprocket and provides SBEC with fuel injection synchronization and cylinder identification. The SBEC uses this information along with crankshaft sensor to determine if fuel injectors and ignition coils are properly adjusted for correct cylinders.

CHARGE TEMPERATURE SENSOR

This sensor is mounted on intake manifold. The sensor measures temperature of incoming intake air/fuel mixture. This information is used by SBEC to adjust air/fuel mixture and turbocharger boost (turbo engines).

COOLANT TEMPERATURE SENSOR (CTS)

The CTS monitors engine coolant temperature. This sensor is mounted in thermostat housing. Coolant temperature information is used by SBEC to slightly richen or lean air/fuel mixture, adjust idle speed and control cooling fans as necessary according to engine temperature. On turbo engines, CTS is also used to control boost levels and spark advance.

CRANKSHAFT ANGLE SENSOR

The crankshaft sensor is mounted on transaxle bellhousing. The sensor reads slots (4 per cylinder) on torque converter drive plate. The SBEC uses this information to determine crankshaft position.

DENOTATION SENSOR

On 4-cylinder turbo models, the detonation sensor is mounted in the intake manifold in such a position so sensor can detect detonation in any cylinder. This sensor generates an input signal to SBEC when detonation occurs. The SBEC uses this input to adjust spark advance and boost schedules.

On 3.3L and 3.8L V6 models, detonation sensor is mounted on engine block where detonation in any cylinder can be detected by sensor. The SBEC uses this information to adjust spark advance.

HALL EFFECT SWITCH

Used only on 4-cylinder engines, Hall Effect pick-up is located inside distributor. This switch supplies SBEC with engine RPM data and ignition timing information. Sensor also supplies SBEC with fuel synchronization data (turbo only). SBEC uses this information to advance or retard ignition timing as necessary.

MANIFOLD ABSOLUTE PRESSURE SENSOR

The MAP sensor monitors manifold vacuum. This sensor transmits information on manifold vacuum and barometric pressure to the SBEC. MAP sensor information is used in conjunction with other sensors to adjust air/fuel mixture.

On turbocharged engines, MAP sensor is also used to adjust spark advance and turbocharger wastegate control.

OPTICAL DISTRIBUTOR

Used only on 3.0L V6 engine, the optical distributor provides engine speed and crankshaft position signals. The SBEC uses this information to control fuel injection, ignition timing and idle speed. (Scheme 2)

Scheme 2

OXYGEN SENSOR

The O2 sensor produces a small electrical voltage (.1-.9 volt) when exposed to oxygen in exhaust gas flow. The O2 sensor is electrically heated for faster switching.

When a large amount of oxygen is present in exhaust gas, O2 sensor will produce a low voltage (.1 volt). With a small amount of oxygen present in exhaust gas, O2 sensor will produce a high voltage (.9 volt).

With the O2 sensor monitoring the oxygen content in exhaust gas, the sensor acts like a rich/lean switch. This information is used by SBEC to adjust air/fuel ratio.

PARK/NEUTRAL SWITCH

The P/N switch is located on transaxle housing. The switch provides an input to the SBEC that indicates what position automatic transmission is in. Input is used to determine idle speed (varying with gear selection), fuel injector pulse width and ignition timing.

THROTTLE BODY TEMPERATURE SENSOR

This sensor is mounted in throttle body. The sensor monitors throttle body temperature so SBEC can richen air/fuel mixture for a hot restart condition.

THROTTLE POSITION SENSOR

The TPS is mounted on throttle body and monitors opening angle of throttle valve. Input voltage to the SBEC from TPS varies from .5 volt at minimum throttle opening (idle) to 4.5 volts at Wide Open Throttle (WOT). The SBEC uses this information along with other sensor inputs to adjust air/fuel ratio.

VEHICLE SPEED SENSOR (VSS)

The VSS is located in transaxle extension housing. The VSS generates 8 pulses per axle shaft revolution. The SBEC will interpret speed sensor input along with throttle position sensor closed throttle input.

This will allow SBEC to differentiate between closed throttle decel and closed throttle idle (vehicle stopped) conditions. During deceleration, SBEC controls Automatic Idle Speed (AIS) motor to maintain a desired manifold pressure value. During idle (vehicle stopped), SBEC controls AIS motor to maintain a desired idle speed.

OUTPUT SIGNALS

Note. Vehicles are equipped with different combinations of computer-controlled components. Not all components listed below are used on every vehicle. For theory and operation on each output component, refer to the system indicated after component.

1. A/C Cut-Out Relay (Miscellaneous)
2. Alternator (Miscellaneous)
3. Automatic Idle Speed (AIS) Motor (Idle Speed)
4. Auto Shutdown (ASD) Relay (Fuel Delivery)
5. Barometric Read Solenoid (Air Induction)
6. CHECK ENGINE Light (Self-Diagnostic System)
7. Electric Exhaust Gas Recirculation Transducer (EET) (Emission Systems)
8. Exhaust Gas Recirculation (EGR) Solenoid (Emission Systems)
9. Fuel Injector(s) (Fuel Injector)
10. Fuel Pump Relay (Fuel System)
11. Ignition Coil(s) (Ignition System)
12. In-Tank Fuel Pump (Fuel Delivery)
13. Lock-Up Torque Converter Solenoid (Transmission Control)
14. Purge Solenoid (Emission Systems)
15. Radiator Fan Relay (Miscellaneous)
16. Speed Control Servo (Miscellaneous)
17. Wastegate Solenoid (Air Induction System)

AUTOMATIC SHUTDOWN (ASD) RELAY

The ASD relay is energized when ignition is on. If SBEC does not receive a distributor signal (camshaft or crankshaft sensor signal on DIS models), SBEC will de-energize ASD relay. On Monaco and Premier, when ASD is de-energized, power to fuel injectors, ignition coil and alternator field is interrupted. On all other models, when ASD is de-energized, power to fuel pump, fuel injectors, ignition coil and O2 sensor heater element is interrupted.

FUEL PUMP RELAY (MONACO & PREMIER)

The fuel pump relay is located in the power distribution center mounted on left strut tower. Relay is controlled by the SBEC and is activated when ignition switch is in Start or Run positions. The relay supplies battery voltage to fuel pump and 02 heater element.

FUEL PRESSURE DAMPER

The fuel pressure damper is only used on 3.3L and 3.8L V6 models. Damper is located downstream of fuel pressure regulator. (Scheme 3) It dampens fuel pressure pulsations which are caused when injectors are opened and closed. An internal rubber diaphragm with an air pocket on one side absorbs pressure pulses.

Scheme 3

FUEL PRESSURE REGULATOR (TBI)

The fuel pressure regulator is a mechanical device located on top of throttle body. Its purpose is to maintain constant fuel pressure at fuel injector. See FUEL PRESSURE (TBI) table. A spring-loaded diaphragm is located inside pressure regulator.

When fuel pump is energized, fuel flows past fuel injector into fuel pressure regulator. The pressure regulator restricts fuel from flowing any further until proper fuel pressure is reached.

When proper fuel pressure is reached, fuel pressure pushes on a spring behind the diaphragm. As fuel pressure moves spring and diaphragm, a return line to fuel tank is uncovered. This allows excess fuel to return to fuel tank keeping fuel pressure constant across injector.

FUEL PRESSURE (TBI)

FUEL PRESSURE REGULATOR (PFI)

The fuel pressure regulator is a mechanical device located on fuel injector rail, downstream of fuel injectors. (Scheme 3) Its purpose is to maintain a constant fuel pressure across fuel injectors. See FUEL PRESSURE (PFI) FUEL PRESSURE (PFI). A spring-loaded diaphragm is located inside pressure regulator.

When fuel pump is energized, fuel flows past fuel injector into fuel pressure regulator. The pressure regulator restricts fuel from flowing any further until correct fuel pressure is reached.

When proper fuel pressure is reached, fuel pressure pushes on a spring behind the diaphragm. As fuel pressure moves spring and diaphragm, a return line to fuel tank is uncovered. This allows excess fuel to return to fuel tank keeping fuel pressure constant across injectors.

FUEL PRESSURE (PFI)

IN-TANK FUEL PUMP (EARLY SHADOW/SUNDANCE CONVERTIBLE WITH 2.5L TBI)

The fuel pump is an immersible electric pump with permanent magnet motor. The pump incorporates a sock attached to pump pick-up. Fuel pump also contains a check valve which restricts fuel movement in either direction when pump is not operational. Voltage to operate pump is supplied through ASD relay.

IN-TANK FUEL PUMP (ALL OTHERS)

The fuel pump is a positive displacement, immersible gerotor pump with a permanent magnet motor. The pump incorporates a sock attached to pump pick-up.

This fuel pump contains 2 check valves. One check valve is used to relieve internal pump pressure and regulate maximum fuel pump output. The other check valve, located near pump outlet, is used to restrict fuel movement in either direction when pump is not operational. Voltage to operate pump is supplied through ASD relay.

THROTTLE BODY INJECTION (TBI)

The fuel injector is an electronic solenoid. The SBEC determines when and for how long the injector should be energized. While electrical current is supplied to the injector, a spring-loaded check ball is lifted from its seat. Fuel then flows in a cone-shaped spray pattern before entering air stream.

PORT FUEL INJECTION (PFI)

The fuel injectors are electric solenoid powered and controlled by SBEC. The SBEC determines when and how long the injector should operate. When an electric current is supplied to the injector, the armature and pintle move a short distance against a spring, opening a small orifice. Since fuel is under high pressure, a fine spray is developed.

AUTOMATIC IDLE SPEED (AIS) MOTOR

The AIS motor adjusts idle speed to compensate for engine load and ambient temperature. The AIS motor varies amount of air by-pass through throttle body.

The SBEC uses coolant temperature, distance (speed) sensor, throttle position and various switch input operations to adjust AIS to obtain optimum idle conditions. Deceleration stall is prevented by increasing airflow when throttle is closed suddenly.

DIRECT IGNITION SYSTEM (DIS)

The crankshaft position sensor senses slots (4 per cylinder, 20 degrees apart) around an extension of the drive plate. Basic timing is preset by crankshaft sensor position and is not adjustable. By using a crankshaft sensor, spark scatter has been eliminated.

A camshaft sensor supplies fuel injection synchronization and cylinder identification information by sensing slots located on camshaft sprocket or camshaft (Monaco and Premier). For sensor location, see CAMSHAFT SENSOR CAMSHAFT SENSOR.

The SBEC fires one coil at a time. This one coil in turn fires 2 spark plugs at once. One cylinder is on compression stroke and the other cylinder is on exhaust stroke. A low primary resistance allows SBEC to fully charge ignition coils for each firing. (Scheme 4)

CAMSHAFT SENSOR

Scheme 4

MAGNETIC IGNITION SYSTEM (2.2L, 2.5L & 2.5L TURBO)

The Hall Effect pick-up is located in the distributor assembly. The pick-up supplies RPM, fuel injection synchronization (Turbo I) and ignition timing data to the SBEC. The SBEC will advance or retard ignition spark as required by the engine running condition.

OPTICAL IGNITION SYSTEM (3.0L)

The timing member is a thin disk, mounted on distributor shaft and driven at 1/2 crankshaft speed. Disk has 2 sets of slots on its surface. (Scheme 2) The outer, high data rate set of slots occurs at intervals of 2 degrees of crankshaft rotation. It is used for ignition timing at engine speeds up to 1200 RPM to increase timing accuracy.

During cranking and idle, engine speed changes with firing pulse of each cylinder. The high data rate signal is used to trigger ignition at correct crankshaft position regardless of these speed changes.

The inner, low data rate set contains 6 slots, which are correlated to piston TDC for each cylinder. This set is used to trigger fuel injection system and operation at speeds greater than 1200 RPM where speed changes due to individual firing pulses are small. This set of slots is also used for ignition timing. Light Emitting Diodes (LED) and photo diodes are mounted in facing positions on opposite sides of the disk, in-line with the slots.

Masks over LED and photo diodes focus light beams onto photo diodes. As each slot passes between diodes, light beam is turned on and off. This creates an alternating voltage in each photo diode, which is converted into on-off pulses by an integrated circuit within distributor. These pulses are transmitted to SBEC.

SINGLE BOARD ENGINE CONTROLLER (SBEC)

SBEC controls the ignition system. During a crank/start mode, SBEC will set a fixed amount of spark advance for an efficient engine start.

IGNITION TIMING ADVANCE CONTROL

The amount of spark advance or retard is determined by inputs that SBEC receives from coolant temperature, engine vacuum and engine RPM sensors. During engine operation the SBEC can supply an infinite number of advance curves to ensure proper engine operation.

AIR ASPIRATOR SYSTEM

Some throttle body fuel injected engines use an air aspirator system. (Scheme 5) This system incorporates a valve that uses exhaust pressure pulsation to draw fresh air from air cleaner into exhaust system.

Scheme 5

This fresh air introduced into exhaust system helps reduce carbon monoxide (CO) and hydrocarbon (HC) emissions. The aspirator valve works most efficiently at idle and slightly off idle conditions. This is when exhaust pulsations are strongest. The aspirator valve remains closed with higher engine speeds.

EVAPORATIVE EMISSION SYSTEM

This system stores fuel vapors from fuel tank, preventing vapors from reaching the atmosphere. As fuel evaporates inside fuel tank, vapors are routed inside vent hoses to charcoal canister, located in wheelwell area, where they are stored until engine is started.

Charcoal canister purging is controlled by a canister purge solenoid. The canister purge solenoid is controlled by SBEC. During engine warm-up and for a short period after hot restarts, SBEC grounds canister purge solenoid causing solenoid to energize.

When canister purge solenoid is energized engine vacuum signal is prevented from reaching charcoal canister. After engine reaches a predetermined operating temperature and a timer has run out, SBEC will de-energize canister purge solenoid. This will allow engine vacuum to purge charcoal canister. Canister purge solenoid will also be de-energized during certain idle conditions so SBEC can update fuel delivery calibration.

EXHAUST GAS RECIRCULATION (EGR) SYSTEM

Note. 2.2L Turbo is not equipped with EGR system. The 2.5L Turbo, 3.3L and 3.8L models equipped with EGR systems are California only.

The EGR system allows a predetermined amount of exhaust gas to enter cylinder with the air/fuel mixture. This dilution of cylinder air/fuel volume reduces Oxides of Nitrogen (NOx) and reduces peak temperatures inside combustion chamber.

2.5L TURBO & EARLY SUNDANCE/SHADOW CONVERTIBLE (2.5L)

The EGR transducer and EGR valve vacuum supply is controlled by the EGR solenoid. EGR solenoid is located on shield on right side of engine compartment and is controlled by the SBEC. EGR solenoid is energized during engine warm-up, closed throttle (idle), wide open throttle and rapid acceleration/deceleration.

ALL OTHERS

The EGR system uses an Electric Exhaust Gas Recirculation Transducer (EET). (Scheme 6) The EET is a back pressure transducer and electric vacuum solenoid combined into a single unit.

Scheme 6

The vacuum solenoid portion of the EET is controlled by the SBEC and is used to regulate vacuum to the transducer portion of EET. The backpressure transducer measures the amount of exhaust gas backpressure on exhaust side of EGR valve. The backpressure transducer then varies the amount of vacuum applied to EGR valve.

This system allows backpressure transducer to provide proper vacuum signal to EGR valve for all engine operating conditions.

POSITIVE CRANKCASE VENTILATION (PCV) SYSTEM

Crankcase and piston blow-by gases are removed from crankcase with manifold vacuum. These gases are introduced into incoming air/fuel mixture and become part of the calibrated mixture. No fresh air enters crankcase with this PCV system.

THERMOSTATIC AIR CLEANER (TAC)

Used only on Throttle Body Injection (TBI) engines, this system controls incoming air temperature into throttle body when ambient temperatures are low. By using heated air, this allows the throttle body to be calibrated leaner, provide better cold driveability and helps prevent throttle body icing.

When ambient temperature is 15°F (9°C) or more above the control temperature, air flow will be through outside outlet. When ambient temperature is less than control temperature, air flows through both air inlets after engine has been started.

With a colder ambient temperature, more air flows past exhaust manifold to heat incoming air. With a warmer ambient temperature, more air flows through air cleaner snorkel by-passing exhaust manifold.

Control of incoming air temperature is controlled by intake manifold vacuum, temperature sensor (inside air cleaner assembly) and a vacuum diaphragm which operates door inside air cleaner snorkel.

Vacuum diaphragm is opposed by a spring. Temperature control occurs during road load conditions or when intake manifold vacuum is above the operating vacuum of vacuum diaphragm.

CHECK ENGINE LIGHT

The Single Board Engine Controller (SBEC) monitors several different circuits of engine control system. If a problem is sensed with a monitored circuit, SBEC will store a trouble code to aid technician in diagnosis of system. The CHECK ENGINE light or Diagnostic Readout Box-II (DRB-II) can be used to read trouble codes.

The CHECK ENGINE light illuminates each time ignition switch is turned on. Light stays on for 3 seconds as a bulb test. If SBEC receives an incorrect signal or no signal from battery voltage input, charging system, Coolant Temperature Sensor (CTS), Manifold Absolute Pressure (MAP) Sensor, Throttle Position Sensor (TPS) or an emission related fault (California vehicles only) CHECK ENGINE light is illuminated. This warns driver that SBEC is in limp-in mode and immediate repairs are necessary. CHECK ENGINE light can also be used to display fault codes. For additional information, see G-TESTS W/ CODES article in the ENGINE PERFORMANCE Section.

A/C CLUTCH RELAY

Note. Although not considered true engine performance-related systems, some controlled devices may affect driveability if they malfunction.

A/C clutch relay is controlled by SBEC and A/C switch. A/C relay is powered by radiator fan relay. This relay is energized during engine operation when A/C switch is closed and blower switch is on.

When SBEC senses low idle speed or Wide Open Throttle (WOT) through Throttle Position Sensor (TPS), it will de-energize A/C relay preventing A/C operation.

ALTERNATOR

Note. Although not considered true engine performance-related systems, some controlled devices may affect driveability if they malfunction.

Chrysler Motors passenger cars use either a Nippondenso or a Bosch alternator. The 3.3L and 3.8L engines use Nippondenso alternators. The 2.2L, 2.5L and 3.0L engines may be equipped with either a Bosch or Nippondenso alternator.

The alternator consists of a rotor, stator, rectifiers, front and rear covers and drive pulley. On all vehicles, voltage regulation is controlled by the Single Board Engine Controller (SBEC).

Alternator diodes convert AC current to DC current. The SBEC monitors critical input and output of the charging system, making sure it is working properly.

The SBEC will store in memory any failures within the monitored circuits. The SBEC will translate a failure in the form of fault codes when on-board diagnostics are entered.

RADIATOR FAN RELAY

Note. Although not considered true engine performance-related systems, some controlled devices may affect driveability if they malfunction.

ALL EXCEPT DYNASTY, FIFTH AVENUE, IMPERIAL & NEW YORKER WITH V6 ENGINES

The Single Board Engine Controller (SBEC) controls radiator fan relay. The radiator fan relay will be energized during the following conditions

1. Fan relay is energized when A/C clutch is engaged.
2. Fan relay will energize at vehicle speeds more than 40 MPH and if coolant temperature reaches 230°F (110°C). Fan relay will turn off when coolant temperature reaches 220°F (104°C). When vehicle speed is less than 40 MPH, fan relay switches on at 210°F (99°C) and off at 200°F (93°C).
3. Fan relay also prevents steaming. Steaming happens when moisture evaporates from outside of radiator when no ram air blows it under the car. Fan relay will energize when ambient temperature is less than 60°F (16°C), with coolant temperature between 100°F (38°C) to 195°F (91°C), engine at idle and fan relay will energize for only 3 minutes.

DYNASTY, FIFTH AVENUE, IMPERIAL & NEW YORKER WITH V6 ENGINES

The Single Board Engine Controller (SBEC) controls radiator fan relay. The SBEC controls fan relay based on coolant temperature and A/C head pressure. Radiator fan relay will be energized during the following conditions

1. When coolant temperature reaches 210°F (99°C) and de-energize at 200°F (93°C) regardless of vehicle speed.
2. When A/C system is engaged.
3. When A/C head pressure reaches 220 psi (15.5 kg/cm 2 ) and will de-energize when head pressure reaches 160 psi (11.2 kg/cm 2 ).

SPEED CONTROL SERVO

This system is electrically actuated and vacuum operated. The controls located on steering wheel consist of: OFF/ON, RESUME/ACCEL AND SET/DECEL buttons. Speed control servo is controlled by SBEC. This system will operate at speeds above 35 MPH.

TRANSMISSION CONTROL

The SBEC controls lock-up of the torque converter through the part-throttle unlock solenoid. Torque converter is locked-up only when in direct drive mode.

See also:
• FUEL PRESSURE (PFI)