Fuel Injection System - Honda Pgm-Fi Acura Integra I

DESCRIPTION

There are 4 sub-systems in the Programmed Fuel-Injection (PGM-FI) system: air intake system, electronic control system, idle control system, and fuel delivery system. Only the air intake and fuel delivery are covered here. The electronic control system is covered in ELECTRONIC ENGINE CONTROL SYSTEM in the COMPUTER ENGINE CONTROL section. For idle control system information, see TUNE-UP - 4-CYL for Integra, or TUNE-UP - V6 for Legend, in the ENGINE PERFORMANCE section.

The system uses an 8-bit microcomputer and various sensors to provide accurate control of air/fuel mixture under all operating conditions. At the precise time a piston is on its intake stroke, fuel is injected into the correct intake manifold runner (sequential injection).

Integra

The fuel pump is an in-line, direct drive type. Fuel is drawn into the pump through a filter, flows around the armature through a one-way valve and is delivered to the engine compartment. A baffle is provided to prevent fuel pulsation.

The fuel pump has a relief valve to prevent excessive pressure. It opens if there is a blockage in the discharge side. When the relief valve opens, fuel only flows from the high pressure side to the low pressure side. A check valve is used to maintain fuel pressure in the line after the pump is stopped to ease restarting.

The pump consists of a rotor and rollers. (Scheme 34) When the rotor turns, the rollers turn and travel along the inner surface of the pump spacer by centrifugal force. The volume of the cavity enclosed by these 3 parts changes, drawing and pressurizing fuel.

Scheme 34

Legend

The fuel pump is installed inside the fuel tank. The fuel pump is comprised of a DC motor, a circumference flow pump, a relief valve for protecting the fuel line systems, a check valve for retaining residual pressure, an inlet port, and a discharge port.

When the engine is started, the main relay actuates the pump, and the motor turns together with the impeller. If fuel flow is obstructed at the discharge side of the fuel line, the relief valve will open to by-pass the fuel to the inlet port and prevent excessive fuel pressure. When the engine stops, the pump stops automatically. A check valve closes after engine stops to retain the residual pressure in the line, helping the engine to restart more easily.

FUEL PRESSURE REGULATOR

The fuel pressure regulator maintains constant fuel pressure to the injectors. The spring chamber of the regulator is connected to the intake manifold to constantly maintain fuel pressure at 36 psi (2.55 kg/cm 2 ) higher than the pressure in the manifold. When the difference between the fuel pressure and manifold pressure exceeds 36 psi (2.55 kg/cm 2 ), the diaphragm is pushed upward, and the excessive fuel is fed back into the fuel tank through the return line.

On Legend models, when the coolant temperature exceeds 221°F (105°C) or the intake air temperature exceeds 176°F (80°C), the Pressure Regulator Cut-Off Solenoid Valve (PRCSV) cuts vacuum to the pressure regulator, to ensure high fuel pressure to the injectors and prevent vapor lock.

Scheme 35

FUEL INJECTOR

The injector is of the solenoid actuated constant-stroke type, consisting of a solenoid, plunger, needle valve and housing. When current is applied to the solenoid coil, the valve lifts up and pressurized fuel fills the inside of the injector and is injected close to the intake valve.

Because the needle valve lift and fuel pressure are constant, the injection quantity is determined by the length of time that the valve is open (i.e., the duration the current is supplied to the solenoid coil). The injector is sealed by an "O" ring and seal ring at the top and bottom.

RESISTOR

To prolong injector life, flow of electrical current to the injector coil is restricted by a resistor installed in series between the electrical power source and the injector coil.

Scheme 36

MAIN RELAY

The main relay is a direct-coupler type. It contains relays for the ECU power supply and the fuel pump power supply. This relay is installed at the back of the fuse box on all models except Legend. On Legend models, it is installed at the left side of the cowl.

ELECTRONIC CONTROL UNIT (ECU)

The ECU contains memories for basic injector discharge durations at various engine speeds and manifold pressures. Basic injector discharge duration, after being read out from the memory, is further modified by signals sent from various sensors to obtain the final discharge duration. Some other functions include starting control, fuel pump control, fuel cut-off control and a fail-safe system monitor.

At start-up, air/fuel ratio must be enriched. The ECU memories contain basic discharge durations to be read out by signals from the starter switch, engine speed and coolant temperature sensors. This provides extra fuel needed for start-up.

When engine speed falls below 100 RPM, electric current to the fuel pump is cut off, preventing injectors from discharging fuel. During deceleration with the throttle valve nearly closed, electric current to the injectors is cut off at speeds over 1200 RPM, contributing to improved fuel economy. Fuel cut off action also takes place when engine speed exceeds 6600 RPM, regardless of the position of the throttle valve.

A fail-safe system monitors sensors and detects any abnormalities in the ECU, ensuring safe driving even if one or more sensors are faulty, or if the ECU malfunctions.

Scheme 37

Legend Sedan

The throttle body is a 2-Bbl. side-draft type with the primary air horn at the top. The lower portion of the throttle valve is heated by engine coolant which flows from the cylinder head. The idle adjusting screw, which increases/decreases by-pass air, and the canister/purge port are located on top of the throttle body. A throttle sensor is attached to the primary throttle valve shaft to send throttle angle information to the fuel injection control unit.

Integra, Legend Coupe

The throttle body is a single-barrel side-draft type. The lower portion of the throttle valve is heated by engine coolant which flows from the cylinder head. The idle adjusting screw which increases/decreases by-pass air and the canister/purge port are located on the top of the throttle body. A throttle sensor is attached to the throttle valve shaft to input the fuel injection control by sensing and sending a signal to the control unit.

DASHPOT

A dashpot is used to slow the closing of the throttle valve as it suddenly approaches the closed position during gear shifting or deceleration. When the throttle is in the closed position, the throttle valve contacts the throttle stop screw.

Scheme 38

THROTTLE CABLE

1. Check that the throttle valve operates smoothly with no binding or sticking. Repair as necessary. Check cable free play at the throttle linkage. Cable deflection should be .39-47" (10-12 mm). If deflection is not within specifications, loosen the lock out and turn the adjusting nut until the deflection is as specified.
2. With the cable properly adjusted, check the throttle valve to be sure it opens fully when the accelerator pedal is pushed to the floor. Also check the throttle valve to be sure it returns to the idle position whenever the accelerator is released.

THROTTLE BODY

1. Start the engine and allow to reach normal operating temperature (cooling fan comes on). Disconnect the vacuum hose (to the canister) from the top of the throttle body. Connect a vacuum gauge to the throttle body. Allow the engine to idle and check that the gauge indicates no vacuum. Check that vacuum is indicated on the gauge when the throttle is slightly off idle.
2. If the gauge indicates no vacuum, check the canister port. If the canister port is clogged, clean it with carburetor cleaner. Stop the engine and check that the throttle cable operates smoothly without binding or sticking.
3. If there are any abnormalities, check for excessive wear or play in the throttle valve shaft, sticky or binding throttle lever at fully closed position, or clearance between throttle stop screw and throttle lever at fully closed position. Replace the throttle body if there is excessive play in the throttle valve shaft or if the shaft is binding or sticking. To clean clogged ports, use a commercially available carburetor cleaner.

TESTING

Note. Before starting testing or trouble shooting, check that other items that affect engine performance are within specifications. Check valve clearance, air cleaner and PCV valve. In addition, check ignition timing, function of the vacuum and centrifugal advance, and condition of the spark plugs. It is also necessary to obtain System Check Harness (07999-60000) to perform some tests.

DASHPOT SYSTEM

1. Check vacuum line for leaks, blockage or a disconnected hose. Disconnect vacuum hose from dashpot, and connect a vacuum pump to it. Apply vacuum and check that vacuum goes out slowly.
2. If vacuum holds or goes out rapidly, replace dashpot check valve and re-test. Connect a vacuum pump and check that rod pulls in and vacuum holds. If vacuum does not hold or rod does not move, replace dashpot diaphragm and re-test.

RELIEVING FUEL PRESSURE

Note. Before disconnecting fuel pipes or hoses, release pressure from system by loosening 6 mm service bolt located at top of fuel filter.

1. Disconnect battery negative cable. Use a box end wrench on the 6 mm service bolt at top of filter, while holding banjo bolt with another wrench.
2. Place a rag or shop towel over bolt. Slowly loosen service bolt one complete revolution at a time. Always replace washer between service bolt and banjo bolt whenever service bolt is loosened to relieve fuel pressure. Replace all washers whenever bolts are removed to disassemble parts.

INSPECTING FUEL PRESSURE

1. Relieve fuel pressure. Remove service bolt on top of fuel filter while holding banjo bolt with another wrench and attach fuel pressure gauge. Start engine. Measure fuel pressure with engine idling and pressure regulator vacuum hose disconnected.
2. Pressure should be 36-41 psi (2.55-2.85 kg/cm 2 ). If fuel pressure is not within specifications, check fuel pump. If pump is okay, check the following: with pressure high, check for pinched or clogged fuel return hose or piping, or a faulty pressure regulator; with pressure low, check for a clogged fuel filter, pressure regulator failure, or leakage in fuel line.

INJECTOR

Note. Check idle speed, ignition timing, valve clearance and idle CO% before performing test.

Engine Runs

1. With engine idling, disconnect injector couplers and note change in idle speed. If idle speed drop is consistent for all injectors, injectors are normal. If idle speed or quality remains the same when a particular injector is disconnected, replace that injector and re-test.
2. Also, check for a clicking sound of each injector using a stethoscope during engine idle. If any injector fails to emit typical clicking sound, check wiring between ECU and injector. If necessary, replace injector.

Engine Will Not Run

1. Remove injector connector and measure resistance between 2 terminals of injector. Resistance should be 1.5-2.5 ohms. If resistance is not within specifications, replace injector. If resistance is as specified, check fuel pressure.
2. If fuel pressure is as specified, check for short-circuit, wire breakage or poor connections in wire between main relay and resistor. Check resistor for open or corroded condition. Check for short-circuiting, wire breakage, or poor connections in the wire between resistor and injector. Check for short-circuit, wire breakage or poor connections in wire between injector and ECU. If all is okay, check the ECU.

FUEL SYSTEM RESISTOR

Disconnect resistor coupler. Check resistance between all resistor terminals, and power terminal "A". (Scheme 39) Resistance should read 5-7 ohms. Replace resistor if any resistance readings are out of specified range.

PRESSURE REGULATOR

Note. If fuel pressure is does not meet specifications, 36-41 psi (2.55-2.85 kg/cm 2 ), check fuel pump and pressure regulator.

Scheme 39

1. Check for pinched, cracked, blocked or broken vacuum hoses. On Legend models, disconnect vacuum hose from pressure regulator and connect a vacuum gauge to pressure regulator. Start engine and allow to idle. Check for vacuum. If there is no vacuum, go to SOLENOID VALVE TEST II.
2. Stop engine. Restart engine. Engine coolant must be above 221°F (105°C) and intake air temperature must be above 176°F (80°C). Check for vacuum. There should be no vacuum. If there is, go to SOLENOID VALVE TEST I. Stop engine. Attach a pressure gauge to service port of fuel filter. Restart engine and check that fuel pressure rises by disconnecting vacuum hose from regulator.

Check for pinched, cracked, blocked or broken vacuum hoses. Check that fuel pressure rises by disconnecting vacuum hose at pressure regulator. If fuel pressure does not rise, pinch return hose 2 or 3 times. If fuel pressure is not within specifications, replace regulator.

Test I (Legend)

Note. Engine coolant temperature must be above 221°F (105°C). Intake air temperature must be above 176°F (80°C).

1. Disconnect solenoid valve connector and attach positive probe of voltmeter to Black/Yellow terminal and negative probe to Light Green terminal. If there is voltage, replace solenoid valve and re-test.
2. If there is no voltage, attach positive probe of voltmeter to Black/Yellow terminal and negative probe to body ground within one minute after restart. If there is voltage, repair open circuit in Black/Yellow wire between solenoid valve and No. 11 fuse. If there is voltage, inspect for open in Light Green wire between solenoid valve and ECU. If wire is okay, check ECU.

Test II (Legend)

1. Start engine. Disconnect vacuum hose from intake manifold and check vacuum. If there is no vacuum, check vacuum port. If there is vacuum, check the vacuum line for proper connection, cracks, blockage or disconnected hose. If the vacuum line is okay, reconnect vacuum hose.
2. Disconnect solenoid valve connector. Attach positive probe of voltmeter to Black/Yellow terminal and negative probe to Light Green terminal. If there is voltage, check for short in Light Green wire between solenoid valve and ECU. If wire is okay, check ECU. If there is no voltage, replace solenoid valve and re-test.

1. Remove main relay, located near fuse box at side cowl. Connect battery positive terminal to No. 4 terminal and battery negative terminal to No. 8 terminal of main relay. Check continuity between terminals No. 5 and No. 7. If there is no continuity, replace main relay.
2. Connect battery positive terminal to No. 5 terminal and battery negative terminal to No. 2 terminal of main relay. Check for continuity between terminals No. 1 and No. 3. If there is no continuity, replace main relay.
3. Connect battery positive terminal to terminal No. 3 and battery negative terminal to terminal No. 8 of main relay. Check for continuity between terminals No. 5 and No. 7 of main relay. If there is no continuity, replace main relay. If main relay is okay, but fuel pump still does not work, proceed to HARNESS TESTING in this article. (Scheme 40)

HARNESS TESTING

1. With ignition off, disconnect main relay coupler. Connect positive probe of voltmeter to wire No. 1 in coupler and negative probe to body ground. Battery voltage should be available. (Scheme 41)
2. If there is no voltage, check wiring harness between battery and main relay as well as ECU fuse, which is located in engine compartment.
3. Connect positive terminal of voltmeter to wire No. 5 of main relay coupler and negative probe to body ground. Turn ignition on. Battery voltage should be indicated. If there is no voltage, check wiring from ignition switch and main relay as well as fuse No. 4.
4. Connect positive probe of voltmeter to wire No. 4 of main relay coupler and negative probe to body ground. Turn ignition switch to "START" position. Battery voltage should be indicated. If there is no voltage reading, check wiring between ignition switch and main relay as well as fuse No. 1.
5. Connect a jumper wire between wire No. 5 and wire No. 7 of main relay coupler. Turn the ignition on. Fuel pump should operate. If fuel pump does not operate, check wiring between the main relay and fuel pump, and the wiring from the fuel pump to the ground.

Scheme 40

Scheme 41

FUEL CUT-OFF SYSTEM

1. Start engine and bring up to normal operating temperature. Ensure that engine idles smoothly. On vehicles equipped with manual transmission, disconnect vacuum hose from dashpot. Using a stethoscope, touch the tip to the injector and confirm injector operation.
2. While listening to an injector, increase engine to 3000 RPM then release the throttle. Clicking of injectors should cease momentarily when throttle is released. If clicking does not cease, check ECU, throttle angle sensor or wiring between injector and ECU.

Scheme 42

1. With ignition off, disconnect coupler from main relay which is located behind fuse box. Using a jumper, connect wires as shown. (Scheme 42) Relieve fuel pressure. Disconnect fuel return pipe from regulator.
2. Turn ignition on and measure amount of fuel flow for 10 seconds. Amount should be 7.8 oz. (230 cc) minimum in 10 seconds at 12 volts.
3. If fuel flow is less than specified, check for fuel pump failure, clogged fuel filter, clogged fuel line, or faulty pressure regulator.
4. If fuel pump problems are suspected, ensure that fuel pump actually runs. It should emit noise when on. If pump does not make noise, run check as outlined in steps 5) and 6).
5. Jack up vehicle and support properly on stands. Remove left rear wheel. Remove fuel pump cover and disconnect Yellow and Black wires. CAUTION: Be sure to turn ignition switch off before disconnecting wires.
6. Check that battery voltage is available at fuel pump wire couplers when ignition is on. Connect positive probe of voltmeter to Yellow wire and negative probe to Black wire.
7. If battery voltage is available, replace fuel pump. If there is no voltage, check main relay and wire harness.

Removal

Disconnect PCV hose from intake air boot. Remove intake air boot clamp at throttle body. Disconnect electrical lead from throttle angle sensor Disconnect all hoses and vacuum lines at throttle body. Remove mounting nuts and remove throttle body from intake manifold.

Scheme 43

Installation

To install, reverse removal procedure. Ensure proper routing of all hoses, vacuum lines and electrical leads. Make necessary idle adjustments.

1. Disconnect negative battery cable. Relieve fuel pressure. Disconnect coupler at injector. Disconnect vacuum hose and fuel return line from pressure regulator.
2. Place a rag or shop towel over hose and tube before disconnecting them. Loosen retainer nuts. Disconnect fuel rail. Remove injector from intake manifold.

1. Slide NEW cushion rings onto injector. Coat new rings with clean engine oil and put them on injectors. Insert injectors into fuel rail. Coat NEW seal rings with clean engine oil and press them into intake manifold. CAUTION: To prevent damage to "O" ring, insert injector into fuel rail squarely and carefully. Install injectors into fuel rail first, then install them into intake manifold.
2. Tighten retainer nuts. Connect vacuum hose and fuel return hose to pressure regulator. Install couplers onto injectors. Turn ignition switch to "ON" position but DO NOT operate starter.
3. After fuel pump runs for approximately 2 seconds, fuel pressure in fuel line rises. Repeat this procedure 2 or 3 times. Then, check for any fuel leaks.

1. Jack up vehicle and support on stands. Remove left rear wheel. Remove fuel pump cover. Remove 3 bolts, then remove pump with its mount. Disconnect fuel lines and electrical leads.
2. Remove clamp and then remove fuel pump. Remove fuel line and damper from pump. DO NOT disassemble fuel pump.

1. Install new fuel pump on its mount. Carefully clean sealing surface of flared fuel line, then install it on fuel pump and tighten flare nut. Reinstall fuel hose and damper on front of pump.
2. Reconnect electrical leads and reinstall fuel pump. Have an assistant turn ignition switch to "ON" position while watching fuel pump connections for leaks. Repeat check 2 or 3 times to ensure there are no fuel leaks.

Scheme 44

Scheme 45

Scheme 46