Fuel Injection System - Egi Mazda RX-7 FC

DESCRIPTION

The Electronic Gasoline Injection (EGI) system precisely meters the amount of fuel injected in each chamber. Fuel delivery system consists of a fuel tank, filter, pump, injectors, pressure regulator and pulsation damper. Air delivery system consists of an airflow meter, air funnel, throttle body, dynamic chamber and intake manifold.

Fuel pump control system consists of fuel pump resistor (turbo), main relay and circuit opening relay. Some models may be equipped with a sub-zero starting assist device for cold start.

OPERATION

The ECU uses input information supplied by various sensors to determine the fuel output. After receiving input information, the ECU determines the correct fuel pressure at the injectors by sending a signal to the pressure regulator control solenoid valve. The ECU also controls the fuel delivery volume by controlling the injector "On" time.

FUEL PRESSURE RELEASE

With engine idling, disconnect fuel pump connector located under rear floor mat. Allow engine to stall then turn ignition off. Cover fuel lines with cloth prior to removal.

FUEL PUMP RESISTOR RELAY (TURBO)

Remove air cleaner and airflow meter. Disconnect fuel pump resistor relay connector. (Scheme 57) Using ohmmeter, test resistance across relay terminals. See FUEL PUMP RESISTOR RELAY RESISTANCE table. Replace resistor if not within specification.

Scheme 57

FUEL PUMP RESISTOR RELAY RESISTANCE

Scheme 58

Scheme 59

CRANK ANGLE SENSOR

Remove the crank angle sensor connector. Note terminal identification. (Scheme 60) Using an ohmmeter, check resistance at specified terminals. Resistance must be within specification. Refer to the CRANK ANGLE SENSOR RESISTANCE SPECIFICATIONS table. Replace sensor if not within specification.

CRANK ANGLE SENSOR RESISTANCE SPECIFICATIONS

Scheme 60

MAIN RELAY

1. Turn ignition on. Check for relay clicking sound when ignition is turned on. Main relay is located behind left strut tower near the firewall.
2. If no operating sound is heard, apply battery voltage and ground to the 2-pronged connector. (Scheme 61) Using ohmmeter, check that no continuity exists between terminals "A" and "B" or "C" and "D" when no voltage is applied. Check that continuity exists between terminals "A" and "B" or "C" and "D" with voltage applied. Replace relay if continuity reading is incorrect.

Scheme 61

CIRCUIT OPENING RELAY

1. Using voltmeter, check for voltage at terminals of circuit opening relay connector. Connect one probe to wire side of connector while connector is still plugged into the relay and the other probe to ground. Note terminal identification. (Scheme 62)
2. With ignition on, 12 volts should exist at the "Fc" and "B" terminals and no voltage should exist at the "Fp", "STA" and "E1" terminals. With airflow meter measuring plate open, 12 volts should exist at the "Fp" and "B" terminals and no voltage should exist at the "Fc", "STA" and "E1" terminals.
3. With ignition switch in "START" position, 12 volts should exist at the "Fp", "B" and "STA" terminals and no voltage should exist at the "Fc" and "E1" terminals.
4. Using ohmmeter, check relay resistance at specified terminals. Replace relay if resistance is not within specification. See «CIRCUIT OPENING RELAY RESISTANCE SPECIFICATIONS»(/mazda/rx-7/fc-1985-1992/remont/testing-diagnostics/#fuel-injection-system-egi) table.

CIRCUIT OPENING RELAY RESISTANCE SPECIFICATIONS

Scheme 62

Injector Resistance

Remove electrical connector from injector. Using ohmmeter, measure resistance between injector terminals. Replace injector if resistance is not within 12-16 ohms.

Injector Fuel Leakage

1. On non-turbo models, remove dynamic chamber. (Scheme 58) On all models, loosen delivery pipe attaching bolts. Remove delivery pipe. Using wire, secure injectors tightly onto delivery pipe. CAUTION: Ensure injectors are securely tied to delivery pipe. If not properly secured, fuel may spray from loose connections.
2. Install jumper wire between 2 terminals of fuel pump test circuit connector. (Scheme 70) Turn ignition on. Check that no fuel leakage exists at injectors. After 5 minutes only a slight amount of fuel leakage is acceptable.

Injector Delivery Volume

1. Using wire, secure injectors tightly onto delivery pipe. Install hose on injector. Install Injector Checker (49 B092 953) on injector. (Scheme 63)
2. Install jumper between 2 terminals of fuel pump test circuit connector. (Scheme 70) Turn ignition on. Connect injector checker to battery voltage. Note injector volume within 15 seconds.
3. Injector volume should be 3.8-4.0 ozs. (.11-.12L) for non-turbo models and 4.5-4.8 ozs. (1.3-1.4L) for turbo models. Check primary and secondary injectors in the same manner.

Scheme 63

Non-Turbo

Start engine and run at idle. Place finger over pulsation damper and ensure damper pulsates. Replace pulsation damper if no operation exists.

Turbo

Information not available.

ATMOSPHERIC PRESSURE SENSOR

Connect voltmeter to "D" terminal of atmospheric pressure sensor and ground. (Scheme 64) Turn ignition on and note voltage. Voltage should be within specification. Refer to the ATMOSPHERIC PRESSURE SENSOR SPECIFICATIONS table. Replace sensor if not within specification.

ATMOSPHERIC PRESSURE SENSOR SPECIFICATIONS

Scheme 64

BOOST OR PRESSURE SENSOR

1. Disconnect vacuum hose from sensor. Connect voltmeter to "D" terminal. (Scheme 65) Using vacuum pump, apply 3.9 in. Hg to sensor.
2. Turn ignition on and note voltage reading. Voltage should be within 2.5-3.5 volts for non-turbo or 2.0-2.5 volts for turbo models. Replace sensor if not within specification.

Scheme 65

INTAKE AIR TEMPERATURE SENSOR

Remove intake air temperature sensor from dynamic chamber. (Scheme 58)or (Scheme 59). Using a heat lamp, ohmmeter and thermometer, measure and record resistance of sensor at various temperatures. Refer to the INTAKE AIR TEMPERATURE SENSOR RESISTANCE specification table. Replace sensor if not within specification.

INTAKE AIR TEMPERATURE SENSOR RESISTANCE

THROTTLE SENSOR

For complete testing and adjustment procedure, see MAZDA RX7 ENGINE CONTROL SYSTEM under COMPUTERIZED ENGINE CONTROLS section.

COOLANT TEMPERATURE SWITCH

1. Remove switch from radiator. Place switch in container of heated coolant with thermometer.
2. Connect ohmmeter to switch terminals. Note temperature at which continuity exists between switch terminals. Continuity should exist with coolant temperature at 59-66°F (15-19°C). Replace switch if not within specification.

COOLANT THERMOSENSOR

1. Remove thermosensor. Place thermosensor in container of heated coolant with thermometer.
2. Connect an ohmmeter to the thermosensor terminals. Note and record resistance at specified temperatures. Refer to the «COOLANT THERMOSENSOR RESISTANCE SPECIFICATIONS»(/mazda/rx-7/fc-1985-1992/remont/testing-diagnostics/#fuel-injection-system-egi) table. Replace if not within specification.

COOLANT THERMOSENSOR RESISTANCE SPECIFICATIONS

AIRFLOW METER

1. Intake air temperature sensor and fuel pump switch are contained in the airflow meter. Determine terminal identification. (Scheme 66)
2. Using ohmmeter, measure resistance between designated terminals. See «AIRFLOW METER RESISTANCE SPECIFICATIONS»(/mazda/rx-7/fc-1985-1992/remont/testing-diagnostics/#fuel-injection-system-egi) table. Reading must be within specification. AIRFLOW METER RESISTANCE SPECIFICATIONS Terminals Ohms Temperature E2 & Vs Non-Turbo 50-500 N/A Turbo 200-600 N/A E2 & Vref Non-Turbo 200-500 N/A Turbo 200-400 N/A E2 & THAa (1) 10,000-20,000 -4°F (-20°C) E2 & THAa (1) 4000-7000 32°F (0°C) E2 & THAa (1) 2000-3000 68°F (20°C) E2 & THAa (1) 900-1300 104°F (40°C) E2 & THAa (1) 400-700 140°F (60°C) E1 & Fc Infinity N/A (1) Intake air temperature sensor.
3. Ensure measuring plate moves freely in airflow meter. Remaining terminals must be checked for fuel pump switch and measuring plate resistances. (Scheme 66) Attach ohmmeter to specified terminals to check fuel pump switch and measuring plate resistance. Refer to the «FUEL PUMP SWITCH & PLATE RESISTANCE SPECIFICATIONS»(/mazda/rx-7/fc-1985-1992/remont/testing-diagnostics/#fuel-injection-system-egi) table.

FUEL PUMP SWITCH & PLATE RESISTANCE SPECIFICATIONS

Scheme 66

SYSTEM TESTING

Note. Following procedure is used prior to testing fuel system.

Scheme 67

Scheme 68

Scheme 69

1. To prepare system for testing, release fuel pressure. Disconnect negative battery cable. Wrap a shop towel around the main fuel hose and disconnect main fuel hose from fuel line. Install adapter between main fuel hose and fuel line. (Scheme 67) Ensure adapter is installed in proper direction. CAUTION: Ensure adapter is not reversed during installation.
2. Disconnect EGR solenoid valve vacuum hose. (Scheme 68)& (Scheme 69). Install Multipressure Tester (49 9200 750A) vacuum hose using a 3-way line connector "Tee".
3. Install negative battery cable. Install multipressure tester leads on battery. Install jumper wire at Yellow wire terminals of check connector. (Scheme 70)& (Scheme 71). Turn ignition on. Check for fuel leaks. Remove jumper wire and tester after system has been tested.

Scheme 70

Scheme 71

Fuel Pump Pressure

1. With multipressure tester installed, move adapter lever so it is straight upward and note fuel pressure. Fuel pressure should be 64-85 psi (4.5-6.0 kg/cm 2 ) for non-turbo models or 71-92 psi (5.0-6.5 kg/cm 2 ) for turbo models.
2. If fuel pressure is not within specification, check wiring harness and main relay operation. If these are okay, replace fuel pump.

Scheme 72

Scheme 73

1. With multipressure tester installed, and engine at normal operating temperature and idling, position adapter lever toward the fuel pump side. (Scheme 67) Note fuel line pressure.
2. Fuel line pressure should be 28.4 psi (2.0 kg/cm 2 ). On non-turbo models, disconnect vacuum hose from pressure regulator. On turbo models, install jumper wire from Orange pressure regulator control solenoid valve to ground. (Scheme 72)& (Scheme 73). On all models, recheck fuel line pressure.
3. With engine idling, fuel pressure should be approximately 34.1-39.8 psi (2.4-2.8 kg/cm 2 ). If not within specification, check wiring harness and pressure regulator solenoid valve. Replace pressure regulator valve if these are okay.

Injection Pressure

1. Perform this test if hesitation or poor acceleration exists. Operate vehicle with multipressure tester installed. The fuel injection pressure should be approximately 34.1-39.8 (2.4-2.8 kg/cm 2 ).
2. If low injection pressure exists, check fuel pump pressure or for clogged fuel filter. If high injection pressure exists, check fuel pressure regulator pressure or for restricted fuel return line.

Inspection Signal (Turbo)

1. Remove intercooler and disconnect intake air temperature sensor connector. (Scheme 74) Attach a 3500-ohm resistor across terminals of connector. Reinstall intercooler.
2. Connect voltmeter across Black and Blue wire terminals of fuel pump connector. DO NOT remove connector while checking voltage.
3. Start and warm engine to normal operating temperature. Turn off ignition. Restart engine. Check that 12 volts exists for approximately 50 seconds and then decreases to approximately 9 volts after 50 seconds. Check fuel pump resistor relay, ECU unit and wiring harness if voltage is not correct.

Scheme 74

SUB-ZERO STARTING ASSIST

1. Ensure fluid supply tank contains adequate amount of fluid. Disconnect "S" terminal connector from starter motor. Remove starting fluid valve from intake manifold.
2. Turn ignition switch to "START" position. Note that no fluid is sprayed from valve with ambient temperature above -4F° (-20C°). Disconnect connector from oil thermo unit located on the oil pan.
3. Touch connector to ground. Turn ignition switch to "START" position. Push air bleed button on air tank. Check that fluid is sprayed from the valve. If fluid is sprayed, check oil thermo unit.
4. Using ohmmeter, check for continuity at oil thermo unit terminals. Replace thermo unit if continuity did not exist at specified temperature. See «OIL THERMO UNIT CONTINUITY»(/mazda/rx-7/fc-1985-1992/remont/testing-diagnostics/#fuel-injection-system-egi) table.

OIL THERMO UNIT CONTINUITY

ON-VEHICLE FUEL INJECTOR OPERATION (NON-TURBO)

1. Using stethoscope, listen for normal "clicking" sound at each injector during idle and acceleration. To check secondary injectors, disconnect vacuum hose from boost sensor. Disconnect throttle sensor connector.
2. Start engine and slowly increase engine speed. Using stethoscope, check that operating sound of secondary injectors occurs above 3500 RPM. If clicking sound is not heard, check crank angle sensor resistance, wiring from crank angle sensor to ECU and EGI main fuse.

ON-VEHICLE FUEL INJECTOR OPERATION (TURBO)

Information not available.

Removal

1. Disconnect negative battery cable. Release fuel pressure. See «FUEL PRESSURE RELEASE»(/mazda/rx-7/fc-1985-1992/remont/testing-diagnostics/#fuel-injection-system-egi__fuel-pressure-release) in this article. Dynamic chamber and throttle body must be removed. (Scheme 58)or (Scheme 59).
2. On turbo models, remove intercooler and oil filler pipe. (Scheme 59) On non-turbo models, remove air funnel. On all models, remove accelerator cable, cruise control cable (if equipped) and metering oil pump connecting rod.
3. Disconnect all electrical connectors from dynamic chamber and throttle body. Mark vacuum hose position. Remove all vacuum hoses and coolant hoses. Remove dynamic chamber.
4. Cover intake manifold ports. Disconnect all fuel lines. Remove delivery pipe from top of injectors. Remove injectors, injector insulators and air bleed sockets (turbo) located below injectors.

Installation

Lubricate new "O" rings and install on injector. On turbo models, install air bleed sockets in correct location. (Scheme 75) To install injectors, reverse removal procedure. Check for fuel leakage before installing dynamic chamber.

Scheme 75

Removal & Installation

Release fuel pressure. See FUEL PRESSURE RELEASE in this article. Disconnect vacuum hose. Cover fuel hoses with rag to avoid spillage. Disconnect and plug fuel lines from regulator. Remove regulator. To install, reverse removal procedure.

FUEL PUMP

1. Release fuel pressure. See «FUEL PRESSURE RELEASE»(/mazda/rx-7/fc-1985-1992/remont/testing-diagnostics/#fuel-injection-system-egi__fuel-pressure-release) in this article. Lift up rear floor mat. Remove fuel pump cover screws and fuel pump cover.
2. Disconnect fuel pump connector, fuel main hose and return fuel hose. Remove fuel pump retaining screws. Remove fuel pump. To install, reverse removal procedure. Check for fuel leakage after installation.

See also:
• FUEL PUMP RESISTOR RELAY RESISTANCE
• FUEL PRESSURE RELEASE