Fuel Injection System - Low Pressure Cfi Mercury Topaz I

COMPONENT TESTING

Note. Specific component testing information not available. Refer to any tests performed during REMOVAL & INSTALLATION or OVERHAUL procedures

DESCRIPTION

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

Fuel is supplied by a low pressure electric fuel pump mounted in the fuel tank. The fuel is filtered and sent to the fuel charging assembly injector fuel cavity and then to the regulator. Fuel delivery pressure is maintained at a nominal value of 14.5 psi (1.0 kg/cm 2 ).

A single injector nozzle is mounted vertically above the throttle plates and connected in series with the fuel pressure regulator. Excess fuel supplied by the pump but not needed by the engine is returned to the fuel tank by a fuel return line.

Low Pressure CFI Fuel Charging Assembly. Scheme 1

AIR & FUEL CONTROL

The fuel charging assembly is comprised of 5 individual components which perform the fuel and air metering function to the engine. The throttle body assembly mounts to the conventional carburetor pad of the intake manifold and provides for packaging of

1. Air Control.
2. Fuel Injector Nozzles.
3. Fuel Pressure Regulator.
4. Fuel Pressure Diagnostic Valve.
5. Cold Engine Speed Control.
6. Throttle Position Sensor.

AIR CONTROL

Airflow to the engine is controlled by a single butterfly valve mounted in a 2 piece, die cast aluminum throttle body. The butterfly valve is identical in configuration to the throttle plates of a conventional carburetor and is actuated by a similar linkage and pedal cable arrangement.

FUEL INJECTOR NOZZLE

The fuel injector nozzle is mounted vertically above the throttle plate. It 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 valve assembly.

An electrical control signal from the Electronic Control Assembly (ECA) activates the solenoid causing the ball to move inward off its seat and allows fuel to flow. The injector flow orifice is fixed, and the fuel supply pressure is constant. Thus fuel flow to the engine is controlled by how long the solenoid is energized.

Low Pressure CFI Fuel Injector Assembly. Scheme 2

FUEL PRESSURE REGULATOR

The pressure regulator is integral to the fuel charging main body near the rear of the air horn surface. The regulator is located strategically to avoid the effects of the supply line pressure drops. Its design is such that it is not sensitive to BACK PRESSURE in the return line to the tank.

A second function of the pressure regulator is to maintain fuel supply pressure upon engine and fuel pump shutdown. The regulator functions as a downstream check valve and traps the fuel between itself and the fuel pump.

The maintenance of fuel pressure upon engine shutdown precludes fuel line vapor formation, allows for rapid restarts and allows for stable idle operation immediately thereafter. It regulates the fuel pressure to the injector nozzles at a constant nominal value of 14.5 psi (1.0 kg/cm 2 ).

THROTTLE ACTUATOR ISC DC MOTOR ACTUATOR

The DC motor actuator controls idle speed by modulating the throttle lever for the required airflow to maintain the desired engine RPM with a warm or cold engine.

An Idle Tracking Switch (ITS), integral with the DC motor, is utilized to determine when the throttle lever has contacted the actuator thereby signaling the need to control engine RPM. The DC motor extends or retracts a linear shaft through a gear reduction system. The motor direction is determined by the polarity of the applied voltage.

THROTTLE POSITION SENSOR

This nonadjustable sensor is mounted to the throttle shaft on the choke side of the fuel charging assembly, and is used to supply a voltage output proportional to the change in the throttle position. The sensor is used by the computer to determine the operation mode (closed throttle, part throttle, and wide open throttle) for selection of the proper fuel mixture, spark and EGR at selected driving modes.

PRELIMINARY CHECKS

Following systems and components must be in good condition and operating properly before beginning diagnosis of fuel injection system

1. All support systems and wiring.
2. Battery connections and specific gravity.
3. Ignition system.
4. Compression pressure.
5. Fuel supply system pressure and flow.
6. All electrical connections and terminals.
7. Vacuum line, fuel hose and pipe connections.
8. Air cleaner and air ducts.
9. Engine coolant level.

ENGINE DOES NOT CRANK

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

ENGINE CRANKS BUT DOES NOT START

1. See that fuel tank contains an adequate amount of fuel. DO NOT assume that fuel gauge is correct. Check ignition system for strong secondary current at spark plugs.
2. If none exists or current is weak, repair ignition system problem before continuing with fuel injection diagnosis. Check fuel lines and fittings for leaks.
3. If no leaks are found, check fuel delivery system for proper operation, pressure and volume. Reset inertia switch if necessary.

HARD TO START - 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. Choke thermostat housing may be incorrectly adjusted. Adjust choke thermostat setting if needed. If it is a tamper-proof type, check for incorrect assembly.
3. Intake manifold or fuel charging assembly gaskets may be leaking. Replace leaking gaskets as needed.

ROUGH IDLE - 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. Fast idle adjustments may be improper. Perform fast idle adjustments. Air cleaner duct vacuum motor may be damaged or stuck open. Replace or service as required. Check for possible vacuum leak.

STALL, STUMBLE, 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 may be low. Service or replace as required. Fuel filter may be clogged. Clean or replace as required. Determine cause.
3. Air cleaner vacuum motor may be damaged. Service or replace as required.

HARD START - HOT

1. Cold enrichment system may not be functioning correctly. Check for proper operation and adjustment. Adjust or replace as required. Fuel pressure may be incorrect. Check fuel pressure regulator.
2. Choke thermostat housing may be incorrectly adjusted. Adjust choke thermostat setting if needed. If it is a tamper-proof type, check for incorrect assembly.
3. Intake manifold or fuel charging assembly gaskets may be leaking. Replace leaking gaskets as needed.

ROUGH IDLE - HOT

Ignition system could be malfunctioning. Check for possible intake vacuum leaks.

STALLS ON DECELERATION OR QUICK STOP

Throttle positioner may be functioning improperly. Service as required. Intake manifold or fuel charging assembly gaskets may be leaking. Replace leaking gaskets as needed.

LACK OF POWER

Fuel filter may be clogged. Check fuel delivery and repair as needed.

REDUCED TOP SPEED/POWER

1. Throttle linkage may be binding. Clean and service as required. Fuel pump volume may be low. Test fuel delivery system.
2. Fuel filter may be clogged. Replace as required. Determine cause. Injectors may be plugged. Repair or replace as needed. Pressure regulator may be damaged. Repair or replace as needed.

SURGE AT CRUISE

1. Fuel filter may be clogged. Replace filter. Determine cause. Fuel pump pressure or volume may be low. Test fuel delivery system.
2. Fuel may be contaminated. Drain fuel and clean system as needed.

PRESSURE CHECK

1. Disconnect electrical connection to inertia switch on right side of trunk. Crank engine for 15 seconds to reduce system pressure. Remove clips on each end of fuel line between fuel filter and fuel charging assembly. CAUTION: Use care to prevent combustion from fuel spillage.
2. Install fuel pressure gauge (T80l-9974-A) using inlet fuel line with the quick connect fitting. Locate gauge between fuel filter and charging assembly inlet. Reconnect inertia switch in trunk. Start engine and check fuel system pressure. Accelerate engine. Pressure should remain stable throughout acceleration.
3. The fuel pump is operating properly if the pressure reaches 13-16 psi (.9-1.1 kg/cm 2 ), the flow is a minimum of 6 oz. (18 cc) in ten seconds and fuel pressure remains at a minimum of 11.6 psi (.8 kg/cm 2 ) immediately after shutdown. If pressure condition is met, but flow is not, check for blocked filters and fuel supply lines. After correcting any blockages, recheck. If flow conditions are still not met, replace fuel pump sender assembly.
4. If both pressure and flow conditions are met, but pressure will not maintain after de-energization, check for leaking injectors or regulator. If both check okay, replace fuel pump-sender assembly. If no flow or pressure is seen, the fuel system should be rechecked for blockages. If no trouble is found, remove the fuel tank and replace the fuel pump sender assembly.
5. Disconnect electrical connection to inertia switch. Crank engine 15 seconds. Remove gauge. Reinstall original fuel line. Reconnect inertia switch. Crank engine and check for leaks.

INERTIA SWITCH

1. In the event of a collision, the electrical contacts in the inertia switch open and the fuel pump automatically shuts off. The fuel pump will shut off even if the engine does not stop running. The engine, however, will stop a few seconds after the fuel pump stops.
2. It is not possible to restart the engine until the inertia switch is manually reset. The inertia switch is located on the left side of the luggage compartment. To reset the inertia switch, depress the button on the switch.

Inertia Switch. Scheme 3

Removal

1. Remove air tube clamp at fuel charging assembly air inlet. Remove electrical connector at inertia switch on right side of the trunk. Release fuel system pressure by cranking engine 15 seconds.
2. Disconnect throttle cable and transmission throttle valve lever. Disconnect electrical connector at ISC, TPS and fuel injector. Disconnect fuel inlet and outlet connections and PCV vacuum line at fuel charging assembly.
3. Remove 2 fuel charging assembly retaining nuts. Remove the assembly. Remove mounting gasket from intake manifold.

Installation

1. Clean mounting surface and position new gasket on intake manifold. Position fuel charging assembly on intake manifold and tighten 2 attaching nuts.
2. Connect electrical connectors to ISC, TPS and fuel injector. Connect fuel inlet, outlet connections and PCV vacuum line at fuel charging assembly. Start the engine and check for leaks.

Fuel Charging Assembly

1. Turn fuel charging assembly over and remove the 4 retaining screws attaching the throttle body to the main body. Separate the throttle body from main body and set aside.
2. Remove and discard the gasket. Remove the 4 fuel pressure regulator retaining screws, applying downward pressure when removing to contain pieces. Remove cover assembly, cup, spring and diaphragm assembly. Remove the regulator valve seat.
3. Remove fuel injector retaining screw and retainer. While applying finger pressure from below injector nozzle, remove injector assembly. Remove injector lower "O" ring from injector cavity in main body and inspect condition of "O" rings.

Throttle Body

Remove the TPS attaching screws. Remove TPS. Remove the ISC motor and bracket assembly from the throttle body. If ISC is to be removed from the bracket, remove the 3 retaining screws.

1. Lubricate lower "O" rings and install in injector cavity. Lubricate injector "O" ring and install injector assembly using care to prevent dislodging lower "O" ring.
2. Install injector retaining screws and retainer. Install fuel pressure regulator valve seat. Install fuel pressure regulator diaphragm assembly, spring and spring cup cover. While applying downward pressure to cover, install 4 retaining screws.

1. Attach the ISC motor to bracket with 3 retaining screws and tighten. Install ISC motor to throttle body with 2 retaining screws. Position the TPS sensor with the connector facing upward to main body.
2. Rotate counterclockwise and align the screw holes. Install retaining screws and tighten. Position main body to throttle body gasket. Install throttle body to main body with 4 retaining screws.

SPECIFICATIONS

Note. Specifications not available. Refer to specifications within TESTING subject in this article.

2.3L HSC Low Pressure CFI System Wiring Diagram. Scheme 4

See also:
• TESTING