Yamaha WaveRunner FX140 Service Manual page 26

Two pulser coils are used: one for cylinders #1 and #4 and one for cylinders #2 and #3.
When the projection on the flywheel magnet passes over the pulser coil, the sensor transmits a sig-
nal to detect the standard position (BTDC 70°) and initial timing (BTDC 10°) of each cylinder.
Crank position projections
Pulser coil signal
for cylinders #1/#4
Pulser coil signal
for cylinders #2/#3
Pulser coil signal
after corrected in
ECU (reference)
The cam position sensor is installed on the exhaust camshaft of cylinder #4.
When the exhaust camshaft passes the cam position sensor, the sensor transmits a signal to the
ECM. After the engine is started, after this signal is input into the ECM twice and the second signal
for cylinders #1 and #4 determines the standard position and initial timing of cylinder #4.
After this, the input standard position and initial timing distinguishe cylinders #3 → #1 → #2, respec-
tively.
Pulser coil
for cylinders
#1/#4
180˚
Initial timing for cylinders
#1/#4 BTDC 10˚
Basic position for cylinders Basic position for cylinders
#1/#4 BTDC 70˚ #2/#3 BTDC 70˚
360˚CA
Cylinder #1
Pulser coil
B70 B10
Cam position sensor
Cam position sensor
(after signal corrected in ECU)
ECU cam position sensor recognition
Pulser coil
for cylinders
#2/#3
360˚
360˚
Initial timing for cylinders Initial timing for cylinders
#2/#3 BTDC 10˚ #1/#4 BTDC 10˚
Basic position for cylinders
#1/#4 BTDC 70˚
Fig. 20
360˚CA
Cylinder #4
Cylinder #1
B70 B10 B70
720˚CA
ECU cam position sensor recognition
Fig. 21
19
Initial timing for cylinders
#2/#3 BTDC 10˚
Basic position for cylinders
#2/#3 BTDC 70˚
360˚CA
Cylinder #4
B10 B70 B10