Renix Throttle Body Fuel Injection (TBFI), Late Type System

Fig. 1 Renix throttle body fuel injection system, late type:

The Renix Throttle Body Fuel Injection (TBFI) system, Fig. 1, is used on Alliance, Encore and GTA models equipped with single point fuel injection. It is a pulse time system that injects fuel into the throttle body above the throttle plate. Fuel is metered to the engine through one electronically controlled fuel injector.

Injection duration is determined by the Electronic Control Unit (ECM) after receiving inputs from Manifold Absolute Pressure (MAP) Sensor, Coolant Temperature Sensor (CTS) or Manifold Temperature (MT) Sensor, Manifold Air/Fuel Temperature (MAT) Sensor, Knock Sensor, Oxygen Sensor, Battery Voltage, Speed Sensor, Starter Motor Relay, Closed Throttle (Idle) Switch, Wide Open Throttle (WOT) Switch, A/C Select Switch, A/C Temperature Control and Transmission Gear Position Indicator (auto. trans. only).

When this system is activated by the ignition switch the fuel pump is activated by the electronic control unit and operates for approximately one second unless the engine is operating or the starter is engaged. All engine sensors are activated and begin providing input for the control unit. The EGR solenoid is activated to block the vacuum to the EGR valve when coolant temperature is below 110°F.

When the engine is started the fuel pump is activated for continuous operation. The idle speed control motor will control idle speed if the throttle position switch is closed. The ignition advance shifts from base ignition timing to the control unit programmed advance curve. The fuel pressure regulator maintains fuel pressure at approximately 14.5 psi by returning excess fuel to tank.