Fuel Delivery and Air Induction: Description and Operation

Fuel and Emissions System Description - Fuel Supply System

Fuel Supply System

Fuel Cutoff Control

During deceleration with the throttle valve closed, current to the injectors is cut off to improve fuel economy at engine speeds over 850 rpm. Fuel cutoff control also occurs when the engine speed exceeds 6,900 rpm, regardless of the position of the throttle valve, to protect the engine from over-revving. When the vehicle is stopped, the PCM cuts the fuel at engine speeds over 5,000 rpm. Engine speed of fuel cut is lower on a cold engine.

Fuel Pump Control

When the ignition switch is turned to ON (II), the PCM grounds PGM-FI main relay 2 which feeds current to the fuel pump control module. The PCM sends a signal to the fuel pump control module to operate the fuel pump for 2 seconds to pressurize the fuel system.When the engine starts, the fuel pump speed is controlled in four levels by the fuel pump control module. The PCM selects the fuel pump speed based on calculating the injector activation time and the engine speed, and then sends an operation command signal to the fuel pump control module. This operation decreases fuel pump noise at low engine speed.

PGM-FI Main Relay 1 and 2

PGM-FI main relay 1 is energized whenever the ignition switch is ON (II) to supply battery voltage to the PCM, power to the injectors, and power for PGM-FI main relay 2 (FUEL PUMP). PGM-FI main relay 2 (FUEL PUMP) is energized to supply power to the fuel pump (fuel pump control module) for 2 seconds when the ignition switch is turned to ON (II), and when the engine is cranking or running.

Transfer Fuel Pump

The fuel in the right side of the fuel tank is drawn over to the left side by the transfer fuel pump.