RX-7 FUEL INJECTION SYSTEM

RX-7 FUEL INJECTION SYSTEM

General Information

The Mazda Electronic Gasoline Injection (EGI) system is a computer controlled, port-type fuel injection system used on 1984-89 RX-7 models equipped with the 13B rotary engine. Fuel is metered to the engine by two solenoid-type injectors that open and close in response to signals from the Electronic Control Unit (ECU). By varying the amount of time the injectors remain open, the ECU precisely controls the fuel mixture according to data on engine operating conditions provided by various engine sensors.

The EGI fuel supply system consists of the fuel tank and lines, fuel filter, electric fuel pump, pulsation damper, fuel pressure regulator, fuel delivery manifold and two solenoid-type fuel injectors. A check and cut valve releases excessive pressure or vacuum in the fuel tank to the atmosphere and prevents the loss of fuel if the vehicle overturns. The fuel system is constantly under pressure, which is regulated to 37 psi (255 kPa).

The fuel pump provides more fuel than the injection system needs for normal operation, with excess fuel being returned to the tank via the fuel return line. The fuel pump is a roller cell type, which is capable of providing 49-71 psi (338-490 kPa) of pressure as measured at the pump outlet.

On 1984-85 models, the pump is located near the fuel tank, under a protective shield on the underbody of the vehicle. The pump connector is located under the storage compartment located behind the driver's seat. On 1986-89 models, the pump is mounted inside the fuel tank.

The pressure regulator and pulsation damper are mounted on the fuel delivery manifold, located under the dynamic chamber just above the injectors. The operation of the fuel delivery system is controlled through the main relay mounted in the engine compartment next to the master cylinder, with power feeding through a fusible link located near the battery.

Relieving Fuel System Pressure

The fuel system remains under high pressure even when the engine is not running. Before disconnecting any fuel lines, release the fuel pressure to reduce the risk of injury or fire. Relieve the fuel pressure as follows:

  1. Locate the fuel pump connector. For more information, refer to the fuel pump removal procedures found later in this section.
  2. Start the engine.
  3. Disengage the fuel pump connector with the engine running.
  4. After the engine stalls from lack of fuel, turn the ignition switch OFF.
  5. Use a shop rag to cover the fuel lines when disconnecting, and plug all fuel lines after they have been disconnected.

Electric Fuel Pump

REMOVAL & INSTALLATION

CAUTION
The fuel system is under pressure even when the fuel pump is not in operation. Always relieve the fuel system pressure before servicing the system. Also, wrap a clean cloth around the fuel connection when loosening to catch any fuel spray from residual pressure and take precautions to avoid the risk of fire.

1984-85 RX-7

  1. Remove the storage compartment located behind the driver's seat and detach the fuel pump connector. Properly relieve the fuel system pressure.
  2. Raise the vehicle and support it safely.
  3. Remove the pump bracket clamp bolt.
  4. Disconnect the inlet and outlet hoses from the fuel pump and plug the lines. Make a note of where each hose connects.
  5. Remove the fuel pump from its bracket.

To install:

  1. Position the fuel pump in its bracket. Unplug, then connect the fuel lines to their proper fittings.
  2. Install the pump bracket clamp bolt, then lower the vehicle.
  3. Attach the fuel pump connector and install the storage compartment.

1986-89 RX-7

  1. Lift up the rear mat.
  2. Unfasten and remove the fuel pump cover.
  3. Relieve the fuel system pressure by running the engine and disengaging the fuel pump electrical connector.
  4. Disconnect and plug the main fuel and fuel return hoses. Make a note of where each hose connects.
  5. Unfasten the retaining screws and remove the fuel pump from the tank.

To install:

  1. Install the fuel pump into the fuel tank and fasten the retaining screws.
  2. Connect the main fuel hose (labeled Ain the illustration) to the Afitting on the pump. Do the same for the Bhose. Secure the hoses with the hose clips and make sure they are tight.
  3. Attach the pump's electrical connector.
  4. Install the fuel pump cover and reposition the rear mat.
The fuel pump is mounted inside the fuel tank, beneath a cover plate-1986-89 RX-7

TESTING

  1. Relieve the fuel system pressure, as previously described.
  2. Disconnect the negative battery cable.
  3. Disconnect the main fuel hose from the main fuel line.
  4. Connect a suitable fuel pressure gauge.
  5. Connect the negative battery cable.
  6. Connect the terminals of the yellow check connector with a jumper wire (see illustration). Turn the ignition switch ONto operate the fuel pump.
  7. Check that the fuel pressure is within the following specifications: Fuel Pump Pressure:
Fuel pump test connector location on RX-7

Throttle Body

REMOVAL & INSTALLATION

The throttle body is part of the vehicle's air intake system. It regulates the amount of air supplied to the engine for combustion.

The throttle body is calibrated at the factory. If there are problems with the adjustment of the throttle adjusting screw or with the action, air tightness, or operation of the throttle, replace the assembly or refer the repair to a qualified shop.

Non-Turbo

  1. Disconnect the negative battery cable.
  2. Detach the accelerator cable from the throttle linkage. Disconnect the cruise control cable (if so equipped).
  3. Disconnect the air funnel. Disconnect the hoses and tubes from the throttle body.
  4. Detach the throttle position sensor connector. Disconnect the metering oil pump connecting rod from the throttle actuating lever.
  5. Unfasten the throttle body retaining screws and remove the throttle body assembly from the dynamic chamber.

To install:

  1. Position the throttle body on the dynamic chamber with a new gasket. Install and tighten the attaching screws.
  2. Connect the metering oil pump connecting rod to the throttle actuating lever. Connect the throttle position sensor.
  3. Connect the air and vacuum hoses. Connect the air funnel and tighten the hose clamps.
  4. Connect the cruise control (if applicable) and accelerator cables. Check and adjust the accelerator cable deflection.
  5. Connect the negative battery cable.

Turbo

In order to remove the throttle body, the dynamic chamber assembly must be removed. Removal of the dynamic chamber is described in Section 3.

Throttle Position Sensor

INSPECTION

  1. Unfasten the throttle sensor connector. Connect a suitable ohmmeter to the sensor as shown in the illustration.
  2. Open the throttle valve and observe the resistance readings. Normal readings are as follows:

Throttle opening A to B:

Throttle opening A to C:

Checking the RX-7's throttle sensor resistance with an ohmmeter
  1. Reattach the connector. If the resistance readings are not as specified, adjust the throttle sensor.

ADJUSTMENT

  1. Warm up the engine to operating temperature, then shut it OFF. Unfasten the connector from the throttle position sensor. Connect the throttle position sensor tester (Part No. 49-F018-001 or equivalent) to the green check connector. Turn the ignition switch ONand check whether one of the tester lamps illuminates.

If such a tester is not available, you can substitute two voltmeters as illustrated. Instead of illumination, look for needle sweeps.

  1. If both lamps illuminate or if neither one does, turn the throttle sensor adjusting screw until only one of them lights. Turn the adjusting screw counterclockwise if both lamps illuminate or clockwise if both lamps DO NOT illuminate.
  2. Reinstall the cap on the screw after adjustment is completed.

Do not apply excessive pressure on the adjusting screw, as it may cause incorrect adjustment.

The RX-7's throttle sensor can be checked with a special test lamp (Part No. 49-F018-001 or equivalent)
Checking current flow to the RX-7's throttle sensor with a pair of voltmeters

Fuel Injectors

REMOVAL & INSTALLATION

  1. Properly relieve the fuel system pressure, then disconnect the negative battery cable.
  2. Remove the throttle body (dynamic chamber) as described earlier in this section.
  3. Disconnect the fuel hose and pipe.
  4. Unfasten the injector connectors.
  5. Remove the pressure regulator and distribution pipe.
  6. Remove the injectors.
  7. Installation is the reverse of removal. Be sure to install new O-rings.
  8. After installation, check for leaks with the fuel pressure applied.

TESTING

Injector Continuity

You can test injectors electrically either on or off the car. Detach the electrical wiring and use an ohmmeter between the two prongs of the electrical connector. The injectors used in the RX-7 should have a resistance of 1.5-3 ohms.

Injector Fuel Leak

  1. Properly relieve the fuel system pressure.
  2. Remove the delivery pipe and fuel injectors. Affix the injectors to the distribution pipe with some wire.

Affix the injectors firmly to the distribution pipe so no movement of the injectors is possible.

  1. Turn the ignition switch to the ONposition. Use a jumper wire and connect the terminals of the fuel pump check connector. Make sure that the fuel does not leak from the injector nozzles.
  2. After approximately five minutes, a very small (slight) amount of fuel leakage from the injectors is acceptable. If this leakage exceeds more than a few drops, replace the injector.
  3. If the injector leaks fuel at a fast rate, replace the injector. If the injectors do not leak, remove all test equipment and install the components in the reverse order of their removal.

Chilton® Automotive Information Systems. © 2004 Thomson Delmar Learning.

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