Fuel Injection System - Tbi Ford Taurus I

DESCRIPTION

Central Fuel Injection (CFI) system is single point, pulse time modulated injection system. Fuel is metered into air intake stream according to engine demands by single injector, which is mounted in throttle body on intake manifold.

Fuel is supplied by low pressure electric fuel pump mounted in fuel tank. Fuel is filtered and sent to injector and then to pressure regulator. Fuel delivery pressure is maintained at 13-17 psi (9.0-1.2 kg/cm 2 ).

Single injector nozzle is mounted vertically above throttle plate. Fuel pressure regulator is downstream from injector in fuel system. Fuel in excess of that needed for engine demand is returned to fuel tank by fuel return line.

Scheme 117

AIR & FUEL CONTROL

Throttle body is comprised of 5 individual components which perform fuel and air metering functions for engine demands. Throttle body assembly mounts to intake manifold and provides for

1. Air Control
2. Fuel Injection
3. Fuel Pressure Regulation
4. Engine Idle Speed Control
5. Throttle Position Sensing

AIR CONTROL

Airflow to engine is controlled by single butterfly valve mounted in a die cast aluminum throttle body. Butterfly valve is identical in configuration to throttle plate of carburetor. It is actuated by a similar linkage and pedal cable arrangement.

FUEL INJECTOR NOZZLE

The fuel injector nozzle is mounted vertically above the throttle plate and is an electro-mechanical device which meters and atomizes the fuel delivered to the engine. The injector valve body consists of a solenoid actuated ball and seat assembly. An electrical control signal from the EEC-IV processor operates the solenoid, allowing the ball to move off its seat and fuel to flow. The injector flow orifices are fixed, and the fuel supply pressure is constant. The amount of fuel flow to the engine is controlled by the amount of time the solenoid is energized.

Scheme 118

FUEL PRESSURE REGULATOR

The pressure regulator is integral to the fuel charging main body and is located near the rear of the air inlet area. It is located so as to nullify the effects of supply line pressure drops and to be insensitive to backpressure in the return line to the tank.

One function of the pressure regulator is to maintain system pressure when the engine and fuel pump are turned off. The regulator functions as a downstream check valve and traps the fuel between itself and the fuel pump.

Maintaining fuel pressure when the engine is turned off, controls fuel line vapor formation and allows for rapid restarts and stable idle operation. The nominal regulated pressure is 14.5 psi (1.0 kg/cm 2 ). However, this value may vary from unit to unit. Pressure is adjusted at the factory to compensate for differences in fuel flow among injectors.

IDLE SPEED CONTROL (ISC) DC MOTOR THROTTLE ACTUATOR

The DC motor actuator controls idle speed by moving the throttle lever. It regulates airflow to maintain the desired engine RPM for both warm and cold engine idle speeds.

An Idle Tracking Switch (ITS), integral to the DC motor, is utilized to determine throttle lever contact. It is controlled by the ECA unit. Motor direction is determined by voltage polarity.

THROTTLE POSITION SENSOR (TPS)

A nonadjustable Throttle Position Sensor (TPS) is mounted to the throttle shaft and is used to supply a voltage output signal proportional to the throttle position. The TPS signal is used by the computer to determine engine operating conditions in relation to throttle position.

PRELIMINARY CHECKS

Check that the following systems and components are in good condition and operating properly before diagnosing problems in fuel injection system

1. Battery condition
2. State of tune
3. Fuel delivery system
4. All wiring and vacuum connections
5. Air cleaner and ducting
6. Cooling system

Engine Does Not Crank

Check for hydrostatic lock (liquid in cylinder). Repair as needed. Check for starting and charging system problems.

Engine Cranks But Will Not Start

1. Check fuel tank contents and fuel gauge accuracy. Check for dirt, water or other contamination in fuel.
2. Check ignition system for strong secondary current at spark plugs. If none exists or current is weak, repair ignition system problem first.
3. Check fuel lines and fittings for leaks. If no leaks are found, check fuel delivery system for proper pressure and volumes. Reset inertia switch if necessary.
4. Check for a defective fuel injector or coolant temperature sensor. Ensure that TPS is not sticking.

Hard Starting - Cold

1. Cold enrichment system may not be functioning correctly. Check TPS and DC motor for proper operation and adjustment. Adjust or replace as required.
2. Intake manifold or throttle body gaskets leaking. Replace leaking gaskets as needed.
3. TPS or Coolant Temperature Sensor (CTS) defective.

Rough Idle - Cold

1. Cold enrichment cycle not functioning. Check fast idle system for proper operation and adjustment. Adjust or replace as required.
2. Air cleaner duct vacuum motor damaged or stuck open. Replace or service as required. Check for vacuum leaks. Check for leaking injector or injector seals.

Stall, Stumble Or Hesitation - Hot Or Cold

1. Cold enrichment system may not be functioning correctly. Check for proper operation and adjustment. Adjust or replace as required.
2. Fuel pump output low. Service or replace as required. Fuel filter clogged. Clean or replace as required after cause is determined.
3. Fuel injector internal filter plugged. Clean or replace injectors as required.
4. Air cleaner vacuum motor damaged. Service or replace as required. Check for bad TPS or coolant temperature sensor.

Hard Starting - Hot

1. Cold enrichment system may not be functioning correctly. Check for proper operation and adjustment. Adjust or replace as required. Fuel pressure not within specification. Check fuel pressure regulator.
2. Intake manifold or throttle body gaskets leaking. Replace leaking gaskets as needed. Check for bad TPS or coolant temperature sensor.

Rough Idle - Hot

Check ignition system. Check for possible intake vacuum leaks.

Stalls On Deceleration/Quick Stop

Throttle position sensor defective. Service as required. Intake manifold or throttle body gaskets leaking. Replace leaking gaskets as necessary.

Lack Of Power

Fuel filter clogged. Fuel injector internal filter plugged. Clean or replace injectors as required. Check fuel delivery and repair as needed.

Reduced Top Speed/Power

1. Throttle linkage binding. Clean and service as required. Fuel pump delivery volume low. Test fuel delivery system.
2. Fuel filter clogged. Fuel injector internal filter plugged. Clean or replace injectors as required. Repair or replace as needed. Pressure regulator damaged. Repair or replace as needed.

Surge At Cruise

1. Fuel filter clogged. Fuel pump pressure or delivery volume low. Test fuel delivery system.
2. Fuel contaminated by dirt or water. Drain fuel and clean system as needed. Fuel injector internal filter plugged. Clean or replace injectors as required.

FUEL DELIVERY SYSTEM TEST

Note. For additional information regarding testing and repair of system components controlled by the EEC-IV computerized engine control system, see appropriate article in COMPUTERIZED ENGINE CONTROLS section.

INERTIA SWITCH

1. In event of a collision, electrical contacts in inertia switch open and fuel pump automatically shuts off. Fuel pump will shut off even if engine does not stop running. Engine will stop due to lack of fuel.
2. It is not possible to restart engine until inertia switch is manually reset. Inertia switch is located behind access door on right side trim panel in rear cargo space of Sable and Taurus station wagon models. Switch is on left side of trunk in all other models. To reset inertia switch, depress button on switch. (Scheme 119)

Scheme 119

Fuel Pump Pressure & Delivery Volume

1. Disconnect wiring at inertia switch. Inertia switch is located behind trim panel in right rear side of cargo area on Sable and Taurus station wagons and behind trim panel on left side of trunk on all other models. Crank engine for at least 15 seconds to reduce system fuel pressure.
2. Disconnect fuel supply line at throttle body. Install In-Line Adapter (D85L-9974-C) and Fuel Pressure Gauge (T87L-9974-A) on throttle body. Reconnect inertia switch and start engine. Check fuel pressure at idle and when accelerating engine. Pressure should remain stable through entire period of acceleration.
3. If gauge readings are correct, disconnect inertia switch. Crank engine for 15 seconds to reduce fuel pressure. Remove gauge and in-line adapter. Install original fuel line and connect inertia switch. Start engine and check for fuel leaks.

FUEL PRESSURE SPECIFICATIONS (1)

INJECTOR RESISTANCE

To measure injector resistance, disconnect injector harness connector. Set ohmmeter on 10-ohm scale. Ensure injector resistance is within specification. See INJECTOR RESISTANCE table.

INJECTOR RESISTANCE

Removal

1. Remove air tube clamp at fuel charging assembly air inlet. Remove electrical connector at inertia switch located on left side of luggage compartment.
2. Release fuel system pressure by cranking engine for 15 seconds. Disconnect throttle cable and transmission throttle lever. Disconnect electrical connector at Idle Speed Control (ISC) motor, Throttle Position Sensor (TPS) and fuel injector.
3. Disconnect fuel inlet and outlet connections. Disconnect PCV vacuum line at fuel charging assembly. Remove 2 retaining nuts and remove fuel charging and throttle body assembly and gasket.

Installation

1. Clean mounting surface and position new gasket on intake manifold. Position fuel charging assembly on intake manifold. Tighten mounting nuts to 14-16 INCH lbs. (18-21 N.m).
2. Connect electrical connectors to ISC, TPS and fuel injector. Connect fuel inlet and outlet connections and PCV vacuum line at fuel charging assembly.
3. Connect throttle cable and transmission throttle lever. Connect electrical connector at inertia switch. Install air tube and clamp at the fuel charging assembly.

Scheme 120

Removal & Installation

1. Release fuel pressure from system. Remove fuel injector retaining screw and retainer. Remove injector and lower "O" ring.
2. To install, lubricate a new lower "O" ring and the injector seat area with clean engine oil (DO NOT use transmission oil). Install lower "O" ring on injector. Lubricate upper "O" ring, clean and lubricate throttle body "O" ring seat.
3. Install injector by centering and applying a steady downward pressure with a slight rotational force. Install injector retainer and retaining screw. Tighten retainer screw to 18-22 INCH lbs. (2.0-2.5 N.m).

FUEL CHARGING ASSEMBLY

Note. To prevent damage to throttle plates, place assembly on a stand or pad.

Disassembly

1. Turn fuel charging assembly over and remove 4 retaining screws attaching throttle body to main body. Separate throttle body from main body and set aside.
2. Remove and discard gasket. If scraping is necessary, be careful not to damage gasket surface. Remove fuel pressure regulator and fuel injector. Remove fittings and filter screen from fuel inlet channel.

Reassembly

1. Install fuel injector and fuel pressure regulator. Attach throttle body with new gasket to body. Tighten screws to 38-44 INCH lbs. (4.3-5.0 N.m).
2. Clean and install screen in fuel inlet channel. Clean loose material from fuel fittings and coat with Loctite (290). Install fuel fittings and tighten to 168-190 INCH lbs. (19-23 N.m).

Scheme 121

Remove Throttle Position Sensor (TPS) attaching screws and remove TPS. Remove ISC motor and bracket assembly from throttle body. If ISC is to be removed from bracket, remove 3 retaining screws.

1. Attach ISC motor, if removed, to bracket with 3 retaining screws and tighten to 44-50 INCH lbs. (5.0-5.6 N.m). Install ISC motor and bracket assembly and tighten to 38-44 INCH lbs. (4.3-5.0 N.m).
2. Position TPS with connector facing upward toward main body. Rotate counterclockwise only and align screw holes. Tighten screws to 13-16 INCH lbs. (1.5-1.8 N.m). NOTE: Failure to install the TPS in this manner may result in excessive idle speeds.
3. Position main body to throttle body gasket. Install throttle body to main body with 4 retaining screws. Tighten to 38-44 INCH lbs. (4.3-5.0 N.m).

Scheme 122

1.9L Escort CFI System Wiring Diagram. Scheme 123

2.5L HSC Sable & Taurus CFI System Wiring Diagram. Scheme 124