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14 - 86 FUEL SYSTEMS

Once the ASD and fuel pump relays have been energized, the engine controller:

²Determines injector pulse width based on coolant temperature, manifold absolute pressure (MAP) and the number of engine revolutions since cranking was initiated.

²Monitors the coolant temperature sensor, camshaft sensor, crankshaft sensor, MAP sensor, and throttle position sensor to determine correct ignition timing.

ENGINE WARM-UP MODE

This is a OPEN LOOP mode. The following inputs are received by the engine controller:

²coolant temperature

²detonation sensor

²manifold absolute pressure (MAP)

²engine speed (crankshaft sensor)

²throttle position

²A/C switch

²battery voltage

The engine controller provides a ground path for the injectors to precisely control injector pulse width (by switching the ground on and off). The engine controller adjusts engine idle speed through the automatic idle speed motor. Also, the controller regulates ignition timing.

CRUISE OR IDLE MODE

When the engine is at operating temperature, this is a CLOSED LOOP mode. During cruising speed the following inputs are received by the engine controller:

²coolant temperature

²detonation sensor

²manifold absolute pressure

²engine speed (crankshaft sensor)

²throttle position

²exhaust gas oxygen content

²A/C control positions

²battery voltage

The engine controller provides a ground path for the injectors to precisely control injector pulse width. The engine controller adjusts 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.

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DECELERATION MODE

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

²coolant temperature

²detonation sensor

²manifold absolute pressure

²engine speed (crankshaft sensor)

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. This indicates a hard deceleration. The engine controller modifies the injector sequence. This helps maintain better control of the air-fuel mixture.

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

²detonation sensor

²manifold absolute pressure

²engine speed (crankshaft sensor)

²throttle position

When the engine controller senses a wide open throttle condition it will de-energize the air conditioning relay. This disables the air conditioning system.

The exhaust gas oxygen content input is not accepted by the engine controller during wide open throttle operation. The engine controller will enrichen the air/fuel ratio to increase performance and compensate for increased combustion chamber temperature.

IGNITION SWITCH OFF MODE

This is an OPEN LOOP 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.

THROTTLE BODY

The throttle body assembly is located on the left end of the intake manifold plenum (Fig. 21). The throttle body houses the throttle position sensor and the 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.

FUEL SUPPLY CIRCUIT

a strainer to prevent water and other contaminants from entering the fuel supply circuit.

Fuel pressure is controlled to a preset level above intake manifold pressure by a pressure regulator. The regulator is mounted on the fuel rail (Fig. 22). The regulator uses intake manifold pressure as a reference.

FUEL PRESSURE REGULATOR

The pressure regulator is a mechanical device located on the fuel rail, downstream of the fuel injectors (Fig. 23). The regulator maintains a constant 380 kPa (55 psi) across the fuel injector tip.

The regulator contains a spring loaded rubber diaphragm that covers the fuel return port. When the fuel pump is operating, fuel flows past the injectors into the regulator, and is restricted from flowing any further by the blocked return port. When fuel pressure reaches 380 kPa (55 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 to keep the fuel pressure constant.

Fig. 3 Solenoid Connections

(4) Verify the harness connector is attached to the MAP sensor (Fig. 4).

Fig. 4 Baro/MAP Solenoid Hose Connections

(5)Check vacuum hose connections between vacuum source and canister purge, wastegate, and barometric read solenoids (Figs. 3 and 4).

(6)Verify hoses are securely attached to vapor canister (Fig. 5).

Fig. 5 Vapor Canister

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

Fig. 6 Ignition Cable Mounting and Attachment

(9) Check oil pressure sending unit electrical connection (Fig. 7).

Fig. 7 Oil Pressure Sending Unit and Crankshaft

Sensor Electrical Connections

(10)Check the camshaft and crankshaft sensor electrical connections (Figs. 7 and 8).

(11)Check radiator fan electrical connector.

(12)Check electrical connector at the coolant temperature sensor (Fig. 9).

(13)Inspect the engine temperature sensor electrical connection (Fig. 9).

(14)Check the power brake booster and speed control connections (Fig. 10).

(15)Inspect the engine and fuel injector harness to main harness electrical connections.

Fig. 8 Camshaft Electrical Connection

Fig. 9 Coolant Temperature and Engine Temperature

Sensor

Fig. 10 Power Brake Booster and Speed Control

Vacuum Hose Connections

(16) Verify that all electrical connectors are fully inserted into relays and that battery connections are clean and tight (Fig. 11 or Fig. 12).

Fig. 11 Engine Compartment Relay Identification AA

Body

Fig. 12 Power Distribution Center AG Body

(17)Check the 60-way electrical connection at the engine controller for damage or spread terminals. Verify that the 60-way connector is fully inserted into the socket on the engine controller (Fig. 13). Ensure that wires are not stretched or pulled out of the connector.

(18)Verify the harness connector is attached to AIS motor. (Fig. 14).

(19)Verify the harness connector is attached to the throttle position sensor. (Fig. 14).

(20)Inspect the hose connections at throttle body (Fig. 14).

(21)Verify all hose connections at the intake manifold are secure (Fig. 15).

Fig. 13 Engine Controller Electrical Connector

Fig. 14 Throttle Body Electrical and Vacuum Hose

Connections

(22)Check vacuum hose connection between vacuum source and fuel pressure regulator (Fig. 16).

(23)Inspect the charge temperature sensor electrical connector (Fig. 16).

(24)Inspect fuel injectors wiring connectors (Fig.

16).

(25)Inspect the detonation (knock) sensor electrical connector (Fig. 17).

(26)Inspect the heated oxygen sensor electrical connector (Fig. 18).

(27)Verify engine ground strap is attached to the engine and the dash panel.

(28)Verify the hose connections on the turbo charger are secure (Fig. 19).

(29)Check the turbocharger bypass valve hose connections.

Fig. 15 Intake Manifold Vacuum Connections

Fig. 16 Vacuum and Electrical Connections

(30)Verify 2-way connector is attached to Distance Sensor (Fig. 20).

(31)Check hose and wiring connections at fuel pump. Check that wiring connector is making contact with terminals on pump.

ON BOARD DIAGNOSTICS

The engine controller has been programmed to monitor many different circuits of the fuel injection system. If a problem is sensed with a monitored circuit often enough to indicate an actual problem, the controller stores a fault. If the problem is repaired or ceases to exist, the engine controller cancels the Fault Code after 51 vehicle key on/off cycles.

Certain criteria must be met for a fault code to be entered into engine controller memory. The criteria

Fig. 17 Detonation (Knock) Sensor Electrical Con-

nector

Fig. 18 Heated Oxygen Sensor

Fig. 19 Hose Connections

may be a specific range of engine RPM, engine temperature, and/or input voltage to the engine controller.

Fig. 20 Distance Sensor Wiring Connector

It is possible that a fault code for a monitored circuit may not be entered into memory even though a malfunction has occurred. This may happen because one of the fault code criteria for the circuit has not been met. For example, assume that one of the fault code criteria for the MAP sensor circuit is that the engine must be operating between 750 and 2000 RPM. If the MAP sensor output circuit shorts to ground when engine RPM is above 2400 RPM (resulting in a 0 volt input to the engine controller) a fault code will not be entered into memory. This is because the condition does not occur within the specified RPM range.

There are several operating conditions for which the engine controller does not monitor and set fault codes. Refer to Monitored Circuits and Non-Monitored Circuits in this section.

Stored fault codes can be displayed either by cycling the ignition key On - Off - On - Off - On, or through use of the Diagnostic Readout Box II (DRB II). The DRB II connects to the diagnostic connector in the vehicle (Fig. 21 or Fig. 22).

Fig. 21 Diagnostic Connector LocationÐAA Body

MONITORED CIRCUITS

The engine controller can detect certain fault conditions in the fuel injection system.