Celica Liftback L4-122 1998cc 2.0L DOHC Turbo (3S-GTE) (1992)
Fuel Pump Speed Control Relay: Description and Operation
Fuel Pump Relay And Resistor Circuit Schematic
PURPOSE
The fuel pump relay controls the speed of the fuel pump based on intake air volume and engine rpm. Passenger compartment noise is reduced
during load engine demand conditions.
OPERATION
When the circuit opening relay sends power from terminal FP, the ECU grounds terminal FPR and sends current to the fuel pump through the fuel
pump resistor. This causes a supply voltage drop, slowing the fuel pump speed slightly. When engine conditions dictate (under ECU control), the
ground from the ECU is interrupted and current is sent to the fuel pump via terminal FP. Fuel pump speed is increased with the increase in voltage.