FUEL PUMP SPEED CONTROL OPERATION


BHE014000140T26

• Controls the fuel pump speed control relay according to the fuel amount required by the engine.

• The required fuel amount is determined by the engine speed, battery positive voltage and the ECT.

• When the required fuel amount exceeds the fixed amount, the PCM turns the fuel pump speed control relay on.

• The circuit driving the fuel pump switches by the fuel pump speed control relay turning on or off.

When Fuel Pump Speed Control Relay Off
– Electric current flows from the fuel pump relay to the fuel pump through the fuel pump resistor. Excess load on the fuel pump is reduced because voltage to the fuel pump is reduced by the fuel pump resistor.
When Fuel Pump Speed Control Relay On
– Electric current flows from the fuel pump relay to the fuel pump through the fuel pump speed control relay. Voltage to the fuel pump flows from the battery because the voltage does not flow through the fuel pump resistor. Due to this, the fuel delivery amount increases by the increase of fuel pump drive force.

1
Main relay
2
B+
3
Fuel pump relay
4
Fuel pump speed control relay
5
To PCM
6
Fuel pump resistor
7
Check connector
8
Fuel pump unit
9
Condenser

Operation Conditions

During cranking

• During cranking, the fuel pump turns on for improved startability.

At low engine speed

• As less fuel is required, the fuel pump speed control relay is turned off.

At high engine speed

• At high engine speed, the fuel pump speed control relay turns on because the required fuel amount increases.