Файл: 92FWD_14.pdf

14 - 26 FUEL SYSTEMS

and fires the injector twice per engine revolution. The engine controller controls engine idle speed and ignition timing. The engine controller controls the air/fuel ratio according to the oxygen content in the exhaust gas.

ACCELERATION MODE

This is a CLOSED LOOP mode. The engine controller recognizes an abrupt increase in throttle position or MAP pressure as a demand for increased engine output and vehicle acceleration. The engine controller increases injector pulse width in response to increased fuel demand.

DECELERATION MODE

This is a CLOSED LOOP mode. During deceleration the following inputs are received by the engine controller:

²coolant temperature

²manifold absolute pressure

²engine speed

²throttle position

²exhaust gas oxygen content

²A/C control positions

²battery voltage

The engine controller may receive a closed throttle input from the throttle position sensor (TPS) at the same time it senses an abrupt decrease in manifold pressure from the manifold absolute pressure (MAP) sensor. This indicates a hard deceleration. The engine controller may reduce injector firing to once per engine revolution. This helps maintain better control of the air-fuel mixture (as sensed through the O2 sensor).

During a deceleration condition, the engine controller grounds the exhaust gas recirculation transducer (EET) solenoid. EGR stops when the controller grounds the solenoid.

WIDE OPEN THROTTLE MODE

This is an OPEN LOOP mode. During wide open throttle operation, the following inputs are received by the engine controller:

²coolant temperature

²manifold absolute pressure

²engine speed

²throttle position

When the engine controller senses a wide open throttle condition through the throttle position sensor (TPS) it will:

²De-energize the air conditioning relay. This disables the air conditioning system.

²Provide a ground path for the electric EGR transducer (EET) solenoid, preventing the EGR system from functioning.

The exhaust gas oxygen content input is not accepted by the engine controller during wide open

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throttle operation. The engine controller will adjust injector pulse width to supply a predetermined amount of additional fuel.

IGNITION SWITCH OFF MODE

When the ignition switch is turned to the OFF position, the following occurs:

²All outputs are turned off.

²No inputs are monitored.

²The engine controller shuts down.

FUEL PRESSURE REGULATOR

The pressure regulator is a mechanical device located at the top of the throttle body (Fig. 17). Its function is to maintain a constant 270 kPa (39 PSI) across the fuel injector tip.

Fig. 17 Fuel Pressure Regulator

The regulator uses a spring loaded rubber diaphragm to uncover a fuel return port. When the fuel pump becomes operational, fuel flows past the injector into the regulator, and is restricted from flowing any further by the blocked return port. When fuel pressure reaches 270 kPa (39 PSI) it pushes on the diaphragm, compresses the spring, and uncovers the fuel return port. The diaphragm and spring constantly move from an open to closed position keeping fuel pressure consistent.

THROTTLE BODY

The throttle body assembly (Fig. 18) is mounted on top of the intake manifold. It contains the fuel injector, pressure regulator, throttle position sensor and automatic idle speed motor. Air flow through the throttle body is controlled by a cable operated throttle blade located in the base of the throttle body. The throttle body itself provides the chamber for metering, atomizing, and mixing fuel with the air entering the engine.

Fig. 3 Canister Purge Solenoid

(4) Verify the wiring connector is attached to the Electric EGR Transducer (EET) solenoid (Fig. 4).

Fig. 4 Electric EGR Transducer (EET) Assembly

(5)Verify vacuum connection at the Electric EGR Transducer is secure and not leaking (Fig. 4).

(6)Verify the connector is attached to the MAP sensor (Fig. 5).

(7)Verify the vacuum hose is attached to the MAP sensor (Fig. 5).

(8)Verify the alternator wiring and belt are correctly installed and tightened.

(9)Verify hoses are securely attached to vapor canister (Fig. 6).

(10)Verify the throttle body wiring connection to main harness is attached (Fig. 7).

(11)Verify the electrical connector is attached to AIS motor (Fig. 8).

Fig. 5 Manifold Absolute Pressure (MAP) Sensor

Fig. 6 Vapor Canister

Fig. 7 Throttle Body Wiring Connection to Main Harness

(12)Verify the electrical connector is attached to the throttle position sensor (Fig. 8).

(13)Verify the electrical connector is attached to the fuel injector (Fig. 8).

Fig. 8 Throttle Body Wiring Connections

Fig. 9 Vacuum Hose from Intake Manifold to PCV Valve

(14)Verify the hose from PCV valve is securely attached to the intake manifold vacuum port (Fig. 9).

(15)Verify vacuum connections on the front and rear of Throttle Body are secure and not leaking (Figs. 10 and 11).

(16)Verify hoses are attached to back pressure transducer or electric EGR transducer (EET) (Fig. 11).

(17)Verify heated air door vacuum connection is connected and not leaking.

(18)Verify power brake and speed control vacuum connectors are tight (Fig. 12).

(19)Verify all ignition cables are in correct order and seated into place (Fig. 13).

Fig. 10 Throttle Body Vacuum PortsÐFront

Fig. 11 Throttle Body Vacuum PortsÐRear

Fig. 12 Power Brake and Speed Control Vacuum

Connection

(20) Verify the electrical connector is attached to coolant temperature sensor (Fig. 14).

Fig. 14 Coolant Temperature Sensor

(22)Verify electrical connector is attached to distributor (Fig. 15).

(23)Verify radiator fan electrical connector is attached to the harness (Fig. 15).

(24)Verify oil pressure switch electrical connector is attached to the switch (Fig. 15).

(25)On automatic transmission equipped vehicles, verify the neutral safety switch electrical connector is attached to the switch (Fig. 16).

(26)On automatic transmission equipped vehicles, check the torque convertor lockup solenoid electrical connection (Fig. 16).

(27)Verify the 60-way connector is fully inserted into the socket on the Engine Controller (Fig. 17).

Fig. 17 Engine Controller Electrical Connector

(28)Verify all electrical connectors are fully inserted into relays and that battery connections are clean and tight (Figs. 18, 19, 20, 21, and 22).

(29)Verify engine harness to main harness connections are fully inserted.

(30)Check the distance sensor connector (Fig. 23).