Yamaha Waverunner VXS VX1800 Service Manual page 309

Symptom 2
Spark plug does not
spark (some cylin-
ders)
Fuel not supplied
(some cylinders)
Compression pres-
sure is low
Cause
Spark plug malfunction
Ignition coil malfunction
Short, open, or loose con-
nection in ignition coil cir-
cuit
ECM malfunction
Fuel injector malfunction
Short, open, or loose con-
nection in fuel injector cir-
cuit
Clogged fuel injector filter
ECM malfunction
Compression leakage
Improper valve timing
Checking step
Check the spark plug.
Check the ignition spark.
Measure the ignition coil input volt-
age (from the battery).
Check the red/yellow (R/Y),
black/red (B/R), black/white (B/W),
black/yellow (B/Y), and black/green
(B/G) ignition coil leads for continui-
ty.
Measure the ECM output peak volt-
age.
Check the fuel injector operation
sound using the YDIS.
Measure the fuel injector resistance.
Measure the fuel injector input volt-
age.
Check the red/yellow (R/Y), pur-
ple/red (Pu/R), purple/black (Pu/B),
purple/yellow (Pu/Y), and pur-
ple/green (Pu/G) fuel injector leads
for continuity.
Clean the fuel injector.
Replace the ECM.
Measure the compression pressure.
Measure the valve clearance.
Check the camshaft for damage.
Check the cylinder head gasket and
cylinder head warpage.
Check the valve and valve seat for
wear.
Check the piston and piston ring for
damage.
Check the cylinder for damage.
Check the timing chain.
9-18
Engine unit troubleshooting
See
page
3-5
7-11
7-11
A-2
7-11
7-29
7-29
7-29
A-2
4-7
—
5-1
3-11
5-35
5-47
5-48
5-76
5-76
5-76
5-37