Fuel Pump Control Circuit: Description

When the engine is cranked, a signal is sent from the power source control ECU's ST SW terminal to the ECM's ST SW terminal. Then voltage travels from the ECM's STA terminal through the park/neutral position switch to the starter relay (Marking: STARTER) coil. The STA terminal also sends a signal to the STA terminal. When the STA signal and NE signal are input to the ECM, the ECM interior's Tr1 turns on, which causes power to be supplied to the circuit opening relay (Marking: C/OPN) coil (C/OPN on). As a result, the fuel pump relay (Marking: F/PMP) actuates, which causes the fuel pump to operate. If the engine is operating and NE signals are being output, the ECM interior's Tr1 is on (C/OPN on), and the fuel pump will continue operating. The fuel pump has a high and low speed setting. When the engine is starting or operating with a heavy load, the ECM interior's Tr2 turns on to actuate the fuel pump relay so that the fuel pump operates at the high speed setting. When the engine is idling or operating with a light load, the Tr2 turns off, and current flows through the fuel pump resistor to the fuel pump so that the fuel pump operates at the low speed setting.