Celica L4-122 1998cc 2.0L DOHC Turbo (3S-GTE) (1990)
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Circuit Opening Relay: Description and Operation
Fuel Pump Relay
Fuel Pump Relay And Resistor Circuit Schematic
The Fuel Pump Relay, mounted in the center of the firewall, controls the speed of the fuel pump based on intake air volume and engine rpm. When the
Circuit Opening Relay sends power from terminal FP, the ECU grounds terminal 1 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 unresisted battery current is sent to the fuel pump via terminal 2. Fuel pump speed is increased with the increase in voltage.
