Fuel Pump Control System - BOMBARDIER Johnson 90 Service Manual

ENGINE CONTROL SYSTEM
ELECTRONIC FUEL INJECTION SYSTEM
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:
lnforms ECM of engine speed.
[ Battery voltage:
ECM
lgnitlon switch:
lnforms ECM of "STARr' signal.
Signal
Fuel pump
ECM
Rectifier
and
regulator
ECM
CPU
Sensor/ switch
signal input
Battery
Fuel pump
Duty cycle algnal for fuel pump
(example: 80% duty)
"ON" time x 1
oo
= duty (%)
OFF
ON
0.8ms
L....__.., _ .__.1--',__. _ .,__L..._Time
1 ms {1cvcle
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 volt­
age.
3-18