Fuel Pump Control System - Suzuki DF 40 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
ECM
main
Rectifier &
relay
regulator
30A fuse
Ignition
switch
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 80 – 90% duty based on the current engine speed and battery voltage.
ECM
CPU
15A
Sensor / switch
fuse
signal input
FP
Fuel pump
ENGINE CONTROL SYSTEM
Signal
ECM
Duty cycle signal for fuel pump
(example : 80% duty)
"ON" time
1 cycle time
OFF
ON
3-18
FP
Fuel pump
× 100 = duty (%)
0.8 ms
Time
1 ms (1cycle)