Mercury 225 EFI Service Manual page 82

IGNITION
Symptom
7. Speed Reduction (RPM
reduced)
8. Engine RPM reduced to
idle only
9. Loss of spark on 1 cylin-
der
Page 2A-26
Cause
7.1 Low battery voltage
ECM requires 8 volts mini-
mum
Fuel Pump requires 9 volts
7.2 Overheat condition
7.3 Oil pump electrical failure
7.4 TPS failure
If TPS fails, rpm is reduced
to idle
8.1 TPS failed
8.2 Battery voltage below 9.5
volts
9.1 Loose wire or pin in connec-
tors between ECM and coil pri-
mary.
9.2 Faulty ignition coil.
9.3 Faulty spark plug.
9.4 Faulty spark plug wire
Note: If spark plug is partially
fouled or the plug gap is too
small, the DDT may indicate the
incorrect cylinder as having an
ignition fault. Example: If the
DDT indicates an ignition fault
on cylinder #4, the problem may
be on the prior cylinder in the
firing order – I.E. cylinder num-
ber #3.
Action
Check battery and/or alternator.
Check electrical connections.
Check water pump impeller/cooling
system.
Check electrical connection.
See 2.2
See 2.2
Use DDT to monitor system
Check connectors.
Replace coil.
Replace spark plug.
Replace spark plug wire.
90-884294 OCTOBER 2001