Fuel Control: Notes

The ECM computes engine speed from the signals sent from the Crankshaft Position sensor. This data is used for determining the time and amount of fuel injection. The CYP Sensor detects the position of No. 1 cylinder. ECM uses signal from the crankshaft/cylinder position sensor to determine duration of fuel injection and to determine when No. 1 cylinder is at TDC for timing sequential fuel injection.

The ECM contains memories for basic ignition timing at various engine speeds and manifold pressures. Ignition timing is also adjusted for engine coolant temperature. A knock control system is also used. When detonation is detected by the knock sensor (KS), the ignition timing is retarded. When the engine is started, the ECM provides a rich mixture by increasing fuel injector duration. When the ignition switch is initially turned on, the ECM supplies ground to the PGM-FI main relay that supplies current to the fuel pump for two seconds to pressurize the fuel system. When the engine is running, the ECM supplies ground to the PGM-FI main relay that supplies current to the fuel pump. When the engine is not running and the ignition is on, the ECM cuts ground to the PGM-FI main relay which cuts current to the fuel pump. Excellent engine performance is achieved through the use of VTEC (Variable Valve Timing and Valve Lift Electronic Control System), intake air bypass control and discharge volume control of the fuel pump.