Fuel Pump Control System - Suzuki DF 90 Service Manual

FUEL PUMP CONTROL SYSTEM

OUTLINE
To supply the optimum fuel amount, the ECM controls the fuel pump drive duty cycle, a repeated ON / OFF
signal, at a specified rate (1000 times a second).
Based on engine speed and battery voltage, the ECM determines the optimum duty (repeating "ON" time rate
within a cycle) and sends this signal to the fuel pump.
CKP sensor :
Informs ECM of engine speed.
Battery voltage
Ignition switch :
Informs ECM of "START" signal.
Battery
charge
coil
Rectifier &
regulator
30A fuse
60A fuse
Battery
CONTROL MODE
BEFORE START :
For 3 seconds after ignition switch is turned "ON", the pump is controlled to operate at 100% duty in order to
initially pressurize the high pressure line.
WHEN CRANKING :
The pump is controlled to operate at 100% duty.
WHEN RUNNING (NORMAL OPERATION) :
The pump is controlled to operate at 70 – 90% duty based on the current engine speed and battery voltage.
ECM
CPU
ECM
main
relay
Ignition FP
switch
Fuel pump
ENGINE CONTROL SYSTEM
ECM
Duty cycle signal for fuel pump
(example : 80% duty)
1 cycle time
OFF
Sensor / switch
signal input
ON
Signal
Fuel pump
"ON" time
× 100 = duty (%)
0.8 ms
1 ms (1cycle)
3-19
FP
Time