Fuel Injection System - Honda Pgm-Fi Honda Civic III

DESCRIPTION

There are 3 main parts of the PGM-FI (Programmed Fuel Injection) system: Air intake system, electronic control and fuel delivery system. To provide the correct air/fuel mixture, engine speed and absolute pressure in the intake manifold are used to determine the amount of fuel to be injected. This is known as a speed-density method of fuel control.

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).

Note. Only primary subsystems which affect fuel system operation will be covered. For further information, see HONDA ELECTRONIC CONTROL SYSTEM in COMPUTERIZED ENGINE CONTROLS section.

Vacuum and Electrical Connections For Honda PGM-FI. Scheme 40

ELECTRIC FUEL PUMP

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 re-starting.

The pump consists of a rotor, rollers and pump spacer. (Scheme 41) 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.

Electric Fuel Pump. Scheme 41

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.

Pressure Regulator Assembly. Scheme 42

FUEL INJECTOR

The injector is solenoid actuated. When current is applied to the solenoid coil, the pintle 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, injection quantity is determined by length of time that valve is open. The injector is sealed by an "O" ring and seal rings at the top and bottom. These seals reduce operating noise.

Fuel Injector Assembly. Scheme 43

RESISTOR

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

MAIN RELAY

Main relay is a direct-coupler type. It contains relays for ECU power supply and fuel pump power supply. This relay is installed at rear of fuse box.

ELECTRONIC CONTROL UNIT

The ECU, which is located under front passenger seat (Civic CRX Si) and under driver's seat (Accord SEi), 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 1 or more sensors are faulty, or if the ECU malfunctions.

CRANK ANGLE SENSOR

Sensors and distributor are designed as an assembly to save space and weight. The unit consists of a pair of rotors (TDC and CYL), and a pick-up for each rotor. Since the rotors are coupled to the camshaft, they turn together as a unit as the camshaft rotates.

The CYL sensor detects the position of cylinder No. 1 as the base for sequential injection. The TDC sensor serves to determine injection timing for each cylinder. The TDC sensor is also used to detect engine speed to read out basic discharge duration for different operating conditions.

Crank Angle Sensor Assembly. Scheme 44

MANIFOLD AIR PRESSURE SENSOR (MAP SENSOR)

The MAP sensor converts air pressure readings into electrical voltage signals and sends them to the ECU. This information with signals from the crank angle sensor is used to read out basic discharge duration from the memory.

Atmospheric Pressure & Manifold Pressure Sensors. Scheme 45

ATMOSPHERIC PRESSURE SENSOR (PA SENSOR)

Like the MAP sensor, the unit converts atmospheric pressure into voltage signals and sends them to the ECU. The signals then modify basic discharge duration to compensate for changes in atmospheric pressure.

COOLANT TEMPERATURE SENSOR (TW SENSOR)

The TW sensor uses a temperature dependent diode (thermistor) to measure differences in coolant temperature. Basic discharge read out is by signals sent from this sensor through the ECU. The resistance of the thermistor decreases with a rise in coolant temperature.

Coolant Temperature Sensor Assembly. Scheme 46

INTAKE AIR TEMPERATURE SENSOR (TA SENSOR)

The TA sensor is a thermistor and is placed in the intake manifold. It acts much like the coolant temperature sensor but with a reduced thermal capacity for quicker responses. Basic discharge duration read out from ECU memory is again compensated for different operating conditions by the signal sent from this sensor to the ECU.

Intake Air Temperature Sensor Assembly. Scheme 47

THROTTLE ANGLE SENSOR

This sensor is essentially a variable resistor. The rotor shaft is connected to the throttle valve shaft and as the throttle valve is moved, resistance varies, altering output voltage to the control unit.

Throttle Angle Sensor Assembly. Scheme 48

OXYGEN SENSOR

The oxygen sensor, by detecting oxygen content of the exhaust gas, maintains a stoichiometric air/fuel ratio. In operation, the ECU receives signals and changes duration during which fuel is injected. It is placed in the exhaust manifold.

IDLE MIXTURE ADJUSTER SENSOR (IMA SENSOR)

The IMA sensor is placed in the control box. The primary objective of this sensor is to maintain correct air/fuel ratio at idle when an injector is replaced. Turning the adjuster changes voltage sent to the ECU which in turn alters fuel discharge duration.

Idle Mixture Sensor Assembly. Scheme 49

STARTER SWITCH

The air/fuel ratio must be rich for starting. During cranking, ECU detects signals from starter switch and increases amount of fuel injected into manifold, according to engine temperature. Amount of fuel injected is gradually reduced when switch is turned off.

THROTTLE BODY

The throttle body is a 2-venturi side-draft type with the primary air horn at the top. The lower portion of the throttle body is heated by engine coolant to prevent icing in winter. The primary throttle valve has a throttle opening sensor located on its shaft. This sensor senses changes in throttle position and signals the ECU where programmed adjustments can be made to the fuel injection system.

On vehicles equipped with a manual transmission, a dashpot is used to prevent abrupt closing of the throttle during gear shifting.

Throttle Body Assembly. Scheme 50

IDLE CONTROL SOLENOID VALVE

When idle speed is reduced due to electrical or other loads on engine, this valve opens to by-pass additional air into intake manifold. This additional air will allow idle speed to increase to its normal speed (700-800 RPM).

Operation depends upon changes in voltage at the FR terminal of the alternator for quicker response. After coolant temperature has reached 104°F (40°C), this valve lowers the fast idle speed in steps during engine warm-up.

To prevent erratic running after engine first fires, valve is opened during cranking and immediately after starting to provide additional air into intake manifold.

FAST IDLE CONTROL SOLENOID VALVE

To prevent erratic running during engine warm-up, a higher idle speed is needed. When engine temperature is cold, this valve opens to by-pass additional air into the intake manifold. This operation is dependent upon coolant temperature and atmospheric pressure.

A/T IDLE CONTROL SOLENOID VALVE

With transmission selector in any position other than "P" or "N", idle speed will tend to be lower. To compensate for this, the valve opens to maintain specified idle speed (700-800 RPM) by allowing additional air to by-pass to the intake manifold.

A/C IDLE CONTROL SOLENOID VALVE

During A/C operation, this valve is turned on. It applies engine vacuum to the A/C idle control diaphragm to open the throttle valve, which raises idle speed to 750-850 RPM. The valve is also on when coolant temperature is low (immediately after starting), thereby ensuring stable idling regardless of position of the A/C switch.

IDLE ADJUSTER (BY-PASS CIRCUIT)

Fuel cut-off takes place at a set position or angle of the throttle valve. If the throttle valve is moved to adjust idle speed, this position or angle will be changed and the system may not cut off fuel supply.

To solve this problem, the throttle body contains an idle speed adjustment screw. This circuit is designed to control the amount of air by-passing into the intake manifold without changing position of the throttle valve.

Idle Adjuster (Air By-Pass Circuit). Scheme 51

FAST IDLE MECHANISM

To prevent erratic running during engine warm-up, it is necessary to raise idle speed. The air by-pass valve is controlled by a thermowax plunger. When the thermowax is cold, the valve opens. When the thermowax is heated, the valve is closed.

With engine cold, additional air is by-passed into the intake manifold so that engine idles faster than normal. When engine reaches operating temperature, valve begins to close, reducing the amount of air by-passed into the manifold.

Fast Idle Mechanism. Scheme 52

Note. Following procedure should be performed after replacement of throttle angle sensor.

1. Align pin of throttle valve shaft groove and temporarily tighten. Disconnect control unit connectors and connect System Checker Harness (07999-PD60000) between control unit and wire harness connector. Connect a digital voltmeter positive probe to terminal C7 of system checker harness and negative probe to terminal C12. (Scheme 55)
2. With ignition on, adjust sensor until it is centered between tangs of throttle stopper lever with lever contacting stop screw. Measure voltage between terminals. There should be 0.48-0.52 volts.
3. If voltage is within specification, test deceleration fuel cut-off device. If deceleration fuel cut-off device does not work, repeat steps 1) and 2).

IDLE SPEED

1. Start engine and bring up to normal operating temperature. Connect a tachometer and check idle speed with headlamps, heater blower motor, rear window defogger, cooling fan and A/C off. Idle speed should be 700-800 RPM. NOTE: To prevent idle control system from operating, pinch vacuum hose No. 10.
2. Adjust idle speed by turning idle adjusting screw. If idle speed cannot be adjusted by turning idle adjusting screw, check out fast idle valve. Check idle controller boosted speed with A/C on. Idle speed should be 700-800 RPM. Adjust idle speed, if necessary, by turning adjusting screw "B". (Scheme 53)

Locations of Idle Speed Adjustment Screws. Scheme 53

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 Checker Harness (07999-60000) to test components.

Scheme 54

1. Disconnect oxygen sensor connector. Start engine and warm up for 2 minutes at 3000 RPM under no load. Raise engine speed to 4000 RPM and release the throttle suddenly at least 5 times.
2. Within 1 minute after engine has been warmed up, measure voltage between connector terminal and body ground as outlined in steps 3) and 4). (Scheme 54): Testing Oxygen Sensor NOTE: If it takes more than 1 minute to complete checks, warm up engine as outlined in step 1).
3. Raise engine speed to 5000 RPM, then lower to 2000 RPM by operating the accelerator pedal. Immediately turn ignition switch off. Voltage at the terminal should read 0.4 volts.
4. Disconnect vacuum hose, between MAP sensor and throttle body, from throttle body. Plug opening in throttle body. Connect a hand vacuum pump to open end of vacuum tube and apply 12 in. Hg vacuum and raise engine speed to 4000 RPM. Voltage reading should be 0.6 volts. Replace sensor if voltages are out of specified ranges.

1. On Accord SEi models, disconnect vacuum hose No. 21 at throttle body. On CRX Si models, disconnect vacuum hose between MAP sensor and throttle body at throttle body. On all models, plug opening in the throttle body. Connect a hand vacuum pump to open end of vacuum tube.
2. Disconnect harness connector from the control unit. Connect System Checker Harness Connector (07999-6000). Apply vacuum to MAP sensor and turn ignition switch on. Connect a digital voltmeter positive probe to C11 terminal of system checker harness and negative probe to C14 terminal. Measure voltage between the 2 terminals. Voltage should agree with chart (Scheme 56) (Scheme 55)& (Scheme 56).

Testing Manifold Air Pressure Sensor. Scheme 55

Scheme 56

1. Disconnect harness connector from the control unit and connect system checker harness to control unit and wire harness connector. Turn ignition switch on.
2. Connect digital voltmeter positive probe to C9 terminal of system checker harness and negative probe to C12 terminal. There should be 2.76-2.96 volts. (Scheme 56): Testing Manifold Pressure Sensor Voltage
3. If voltages are out of range, check for open or short circuit between ECU and atmospheric pressure sensor. Replace sensor if necessary.

1. On Accord SEi models, open control box No. 1 and remove rivets securing IMA sensor. Disconnect IMA sensor 3-pole connector. Measure resistance between Brown and Green terminals (Scheme 57)while turning adjustment screw.
2. On CRX Si models, measure resistance between Green and Yellow terminals (Scheme 57)of control box coupler. On all models, specified resistance value is 0.25-6.2 k/ohms. Replace sensor if resistance is out of range.

Testing Idle Mixture Sensor. Scheme 57

INTAKE AIR TEMPERATURE/COOLANT TEMPERATURE SENS (TA/TW SENS)

1. Disconnect the connector and remove the TA/TW sensor from the inlet manifold/cylinder head. To test sensor, suspend it in cold water and heat water slowly. Measure resistance between terminals.
2. Specified readings are 0.98-1.34 k/ohms at 95°F (40°C) and 0.22-0.35 k/ohms at 176°F (80°C). Replace sensor if it is out of specified ranges.

Note. If either CYL or TDC sensor is faulty, they should be replaced as an assembly.

CYL Sensor

1. Release connector from CYL sensor. Measure resistance between White terminal and Red terminal at sensor. Specified resistance should read 0.65-0.85 k/ohms.
2. Measure insulation resistance between White/Red terminal of sensor and crank angle sensor housing. Resistance should read 100 k/ohms or more.

Testing CYL and TDC Sensors. Scheme 58

TDC Sensor

1. Release connector of crank angle sensor. Measure resistance between Brown terminal and Blue terminal at sensor. Resistance should read 0.65-0.85 k/ohms.
2. Measure insulation resistance between Brown/Blue terminal and crank angle sensor housing. Resistance should read 100 k/ohms or more.

1. Release connector of throttle angle sensor. Measure resistance at sensor between Yellow and Green terminals (Accord SEi) or between Brown/Black terminal and Yellow/Red terminal (CRX Si) (Scheme 59)
2. Specified resistance value is 3.2-7.2 k/ohms. If resistance is outside specified range, adjust installation position of sensor and retest. Replace sensor if necessary.

Testing Throttle Angle Sensor. Scheme 59

Scheme 60

Scheme 61

1. The idle control solenoid valve is activated by commands from ECU. When the solenoid valve opens, this causes vacuum in vacuum hose, between the air filter and solenoid valve, and increases idle speed for a short period after starting the engine and whenever electrical loads are turned on. NOTE: Vacuum will disappear when engine RPM is raised over 1500 RPM (Accord SEi) or 1700 RPM (CRX Si) by operating the throttle.
2. While solenoid valve is being activated, 9 volts or higher should be available between Black/Yellow (+) and Green/Black (-) (Accord SEi) or Black terminal (+) and Light Green (-) (CRX Si) of valve leads.
3. On Accord SEi models, disconnect wire harness from idle control solenoid valve. Disconnect vacuum hose No. 26 from airflow tube. Pump air into vacuum hose No. 26. There should be no airflow.
4. Connect battery positive terminal to Black/Yellow terminal of solenoid valve, and negative battery terminal to Green/Black terminal. Disconnect vacuum hose No. 28 from intake manifold. Pump air into vacuum hose No. 26. There should be airflow. (Scheme 60) (Scheme 60): Testing Accord SEi Idle Control Solenoid Valve
5. On CRX Si models, open control box lid and disconnect wire harness from the control box. Disconnect vacuum hose between idle control solenoid and No. 10 vacuum hose. (Scheme 61) (Scheme 61): Testing CRX Si Idle Control Solenoid Valve
6. Apply vacuum to hose. It should hold vacuum. Connect battery positive terminal to Black terminal of control box and negative battery terminal to Light Green terminal. Apply vacuum to the hose. It should not hold vacuum.

Accord SEi

1. Fast idle control solenoid is opened when coolant temperature is below 5°F (-15°C). If coolant temperature is below 104°F (40°C), it is energized only when atmospheric pressure is 26 in. Hg or less. In either case, vacuum produced in the vacuum hose No. 18.
2. When valve is open, 9 volts or more should be available between the Black/Yellow terminal (+) and Blue/Black terminal (-) of wire harness at control box No. 1.
3. Disconnect wire harness from No. 1 control box. Disconnect vacuum hose No. 18 from airflow tube. Pump air into vacuum hose No. 18 from the airflow tube. There should be no airflow.
4. Connect battery positive terminal to the Black terminal of control box No. 1 coupler and battery negative terminal to the Orange terminal. Disconnect vacuum hose No. 23 from intake manifold. Pump air into vacuum hose No. 18. There should be airflow. (Scheme 62)

Testing Accord SEi Fast Idle Control Solenoid Valve. Scheme 62

CRX Si

Note. The fast idle control solenoid valve is opened when atmospheric pressure is 26 in. Hg or less. Vacuum is produced in the vacuum hose between solenoid valve and air filter.

Scheme 63

1. When valve is open, 9 volts or more should be available between Black terminal (+) and Yellow terminal (-) of wire harness of control box. Open control box lid and disconnect wire harness from control box.
2. Disconnect vacuum hose between fast idle control solenoid and No. 10 vacuum hose. Apply vacuum to the hose. It should hold vacuum. (Scheme 63) (Scheme 63): Testing CRX Si Fast Idle Control Solenoid Valve
3. Connect battery positive terminal to Black terminal of control box coupler, and battery negative terminal to Yellow terminal. Apply vacuum. It should not hold vacuum.

Accord SEi Only

Note. The A/T idle control solenoid valve is energized when selector lever is in D4, D3, 2 and R. When solenoid valve is energized, it opens, causing vacuum in vacuum hose No. 18, between valve and airflow tube. While valve is energized, 9 volts or more should be available between Black/Yellow terminal (+) and Green terminal (-) of No. 1 control box.

1. Disconnect wire harness from No. 1 control box. Disconnect vacuum hose No. 18 from airflow tube. Pump air into vacuum hose No. 18. There should be no airflow.
2. Connect battery positive terminal to Black terminal of No. 1 control box coupler and battery negative terminal to Yellow/Black terminal. Disconnect vacuum hose No. 23 from intake manifold. Pump air into vacuum hose No. 18. There should be airflow. (Scheme 64)

Testing Accord SEi Auto. Trans. Idle Control Solenoid Valve. Scheme 64

Note. The A/C idle control solenoid valve is activated when the A/C switch is turned on. When the solenoid valve is activated, vacuum is generated in vacuum hose No. 19 between the solenoid valve and idle diaphragm. There should be 9 volts or more between the Black/Yellow terminal (+) and the Blue/Yellow (-) of No. 2 control box harness.

1. Disconnect wire harness from No. 2 control box. Disconnect vacuum hose No. 19 from the airflow tube. Start engine and feel for vacuum at the opening of the solenoid valve. There should be no vacuum.
2. Start engine and feel vacuum at the opening of the solenoid valve. There should be vacuum. (Scheme 65)

Testing Accord SEi A/C Idle Control Solenoid Valve. Scheme 65

Note. Perform inspection only after engine has been warmed up to normal operating temperature (radiator fan comes on twice).

1. Disconnect vacuum hose to purge canister at the top of throttle body and connect a vacuum gauge to throttle body. Start engine and warm up to normal operating temperature. Ensure there is NO VACUUM.
2. Check vacuum reading when throttle is opened slightly from idle. Stop engine and ensure throttle cable operates smoothly without binding or sticking. If there are any abnormalities in the above mentioned steps, check for: Excessive wear or play in throttle valve shaft. Sticky or binding throttle valve lever at full close position. Clearance between throttle stop screw and throttle lever at full close position. There should be no clearance. Purge canister port should be located upstream of primary throttle valve in full closed position.

Testing Throttle Body Assembly. Scheme 66

FAST IDLE VALVE

Note. The fast idle valve is factory set and should not be disassembled. Check PCV system tubing for breakage, disconnection and clogging. Ensure throttle valves are fully closed.

Scheme 67

1. If engine idle speed is too high after engine is warmed up, ensure that engine is adequately warmed up. Check whether idling control function is normal.
2. To do so, remove fast idle valve cover. Ensure valve is completely closed. If not, air is being sucked from valve seat area. It can be detected by putting finger on the valve seat area. (Scheme 67) (Scheme 67): Testing Fast Idle Valve for Air Leaks
3. If any sucking is felt, valve is leaking. Replace fast idle valve and adjust idle speed. See «ADJUSTMENTS»(/honda/civic/iii-1983-1987/remont/testing-diagnostics/#fuel-injection-system-honda-pgm-fi).
4. If idle speed is too low after engine is warmed up, remove idle adjusting screw. Wash idle adjusting screw and air by-pass channel with carburetor cleaner. Readjust idle speed. NOTE: If fast idle speed is low when engine coolant temperature is below 140°F (40°C), fast idle valve may be stuck closed. Fast idle speed should be 1250-2250 RPM.
5. To check for fast idle speed being too low, remove fast idle valve assembly from throttle body. Apply cold water to cool down thermowax element within fast idle valve to 41-86°F (5-30°C).
6. Blow through "Part A" of fast idle valve and check that a fairly large amount of air flows without resistance. (Scheme 68) If air does not flow or resistance is large, replace fast idle valve and adjust idle speed.

Testing Fast Idle Valve for Airflow. Scheme 68

DASHPOT SYSTEM

1. Slowly open throttle arm until dash pot rod is fully extended. Release throttle arm and measure time until throttle arm contacts stop screw. Time should be less than 2 seconds.
2. If time is over 2 seconds, replace dashpot check valve and retest. If rod does not operate, check for bound linkage, or for clogged check valve or vacuum line. If they are okay, replace dashpot.

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 the fuel filter, while holding banjo bolt with another wrench.
2. Place a rag or shop towel over bolt. Slowly loosen service bolt 1 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.

INJECTOR

Note. Check idle speed, ignition timing, valve clearance and idle CO % before condemning injector(s).

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.
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.

FUEL SYSTEM RESISTOR

Disconnect resistor coupler. Check resistance between all resistor terminals (E, D, C and B), and power terminal (A). (Scheme 69) Resistance should read 5-7 ohms. Replace resistor if any resistance readings are out of specified range.

Testing Fuel System Resistor. Scheme 69

PRESSURE REGULATOR

Note. If fuel pressure is does not meet specifications (33-39 psi/2.53-2.57 kg/cm 2 ), check fuel pump first, then pressure regulator.

Check for pinched 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.

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 terminal No. 5 and terminal 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 terminal No. 1 and terminal 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 terminal No. 5 and terminal 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»(/honda/civic/iii-1983-1987/remont/testing-diagnostics/#fuel-injection-system-honda-pgm-fi). (Scheme 70)

Testing Main Relay. Scheme 70

Scheme 71

1. With ignition switch 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 71) (Scheme 71): Testing Main Relay Wire Harness
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 switch 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. 1 and wire No. 7 of main relay coupler. Fuel pump should operate. If fuel pump does not operate, check wiring between battery and fuel pump and wiring from fuel pump to ground (Black wire).

FUEL CUT-OFF SYSTEM

1. Start engine and bring up to normal operating temperature. Ensure that engine idles smoothly. On vehicles equipped with M/T, disconnect vacuum hose from dashpot. Use a stethoscope to 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.

FUEL PRESSURE TESTING

Note. Relieve fuel pressure before proceeding with this test.

1. Remove service bolt at fuel filter and attach fuel pressure gauge. Start engine. Measure fuel pressure with engine idling and vacuum hose disconnected from pressure regulator. Pressure should read 33-39 psi (2.53-2.57 kg/cm 2 ).
2. If fuel pressure is not as specified, first check fuel pump. If pump is okay, check the following: If fuel pressure is higher than specified, inspect for pinched or clogged fuel return line or piping, or check for faulty pressure regulator. If fuel pressure is lower than specified, check for clogged fuel filter, pinched or clogged fuel hose from fuel tank to fuel pump, pressure regulator failure, leakage in fuel lines, or pinched, broken or disconnected regulator vacuum hose.

FUEL PUMP

Scheme 72

1. With ignition switch off, disconnect coupler from main relay which is located behind fuse box. Using a jumper, connect wires (Scheme 72) Relieve fuel pressure. Disconnect fuel return pipe from regulator. (Scheme 72): Testing Fuel Pump
2. Turn ignition switch on and measure amount of fuel flow for 10 seconds, then turn ignition switch off. 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 switch is on. To do so, 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 & Installation

To remove sensor, remove 2 shear screws from throttle body. To install, align pin of sensor with throttle valve shaft groove and tighten temporarily. Perform adjustment procedure as outlined in THROTTLE ANGLE SENSOR in ADJUSTMENTS section.

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.

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 fu l 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 you watch fuel pump connections for leaks. Repeat check 2 or 3 times to ensure there are no fuel leaks.

FUEL FILTER

1. Filter should be replaced every 60,000 miles or whenever fuel pressure drops below specifications with vacuum hose disconnected at pressure regulator.
2. Disconnect battery. Place a shop towel under and around fuel filter. Relieve fuel pressure. Remove two-12 mm sealing bolts from filter.

To install fuel filter, reverse removal procedure. Be sure to replace all sealing washers between bolts, lines and filter.

See also:
• ADJUSTMENTS