Mercury 40 Service Manual page 75

IGNITION
Weak Spark Condition
(Low Primary Voltage)
Timing Fluctuates
Note: It is considered normal for the timing
to fluctuate approximately 1 - 2 within the
designated timing window.
*Recommended Test (cont.)
(1) DVA TEST (Direct Voltage Adapter)
(2) OHM TEST (Resistance Testing)
(3) Replace Component and Retest
(4) Mechanical Test/Repair
PROBLEM/CONDITION
Timing Will Not Advance
Engine Misfires At High RPM
Engine Hard To Start Cold
Engine Hard To Start Hot
Engine Will Not Run Over 2000 RPM
Page 2A-14
Ground Connection at:
a - ignition coil
b - (CDI) unit
c - stator
High Resistance To Ground at:
a - stop/lanyard switch (water/corrosion)
Weak Charge Coil
(CDI) Unit Failure
Ignition Coil/High Tension Lead(s)
Spark Plug(s)
Spark Plug Cap (Resistor)
Loss Of Oil Pressure:
a - timing retards and fluctuates, rpm will
drop below 2000 rpm
Flywheel Key Sheared
(CDI) Unit
Probable Cause
Low Oil Pressure:
a - timing retards and fluctuates, rpm
will remain below 2000 rpm
(CDI) Unit
Low Oil Pressure:
a - timing retards and fluctuates, rpm
will remain below 2000 rpm
Ignition Coil/High Tension Lead(s)
Spark Plug Cap(s) 5k Ω Resistor
Spark Plug(s)
(CDI) Unit
Ground Connection:
a - (CDI) unit
b - ignition coil
c - stator
Debris In Carburetor Enrichener Circuit
Weak Spark Condition
Throttle Plate in Open Position
Weak Spark Condition
Vapor Lock
Low Oil Pressure
a - timing retards and fluctuates, rpm
will remain below 2000 rpm
Stator
Ignition Coil/High Tension Lead(s)
(CDI) Unit
Spark Plug(s)
2
2
2
2
1-2
1-3
2
3
2
4
4
3
*Perform
Test No.
4
1-3
4
2
2
3
1-3
2
2
2
4
1
4
4
1
4
1-2
2
1-3
3
90-828631R3 MARCH 1999