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Two Cylinder Engines 1994-1996 (With the 18495A9, A14, A16, A20, A21 or A30 Switch Box)

(Continued)

WILL NOT ACCELERATE BEYOND 3000-4000 RPM:

  • 1.

    Connect an inductive Tachometer to each cylinder in turn and try to isolate the problem. A single cylinder dropping fire will likely be the switch box or ignition coil. All cylinders misfiring usually indicate a bad stator.

  • 2.

    Connect a timing light to #1 cylinder and verify that the timing is advancing. Also check to make sure the timing is not retarding too early.

  • 3.

    Connect a DVA meter between the stator’s blue wire and black wires. Perform a running test. The DVA voltage should jump up to well over 200V and stabilize. A drop in voltage right before the problem occurs indicates a bad stator. (read the blue wire to engine ground if the engine has a red stator kit installed).

  • 4.

    Connect a DVA meter between the stator’s red wire and black wires. The DVA voltage should show a smooth climb in voltage and remain high through the RPM range. A reading lower than the reading on the blue wire indicates a bad stator.

  • 5.

    If both cylinders become intermittent, replace the switch box.

  • 6.

    Perform a high-speed shutdown and read the spark plugs. Check for water. A crack in the block can cause a miss at high speed when the water pressure gets high, but a normal shutdown will mask the problem.

  • 7.

    Remove the flywheel and check the triggering and charge coil flywheel magnets for cracks or broken magnets.

Two Cylinder Engines 1994-2006 (With the 855721A3 & A4 Switch Box)

NO SPARK ON ANY CYLINDER:

1.

Disconnect the black/yellow stop wire AT THE PACK and retest. If the engine’s ignition now has spark now, the stop circuit has a fault-possibly the key switch, harness or shift switch.

  • 2.

    Check the cranking RPM. A cranking speed less than 250-RPM will not allow the system to fire properly.

  • 3.

    Check the stator and trigger resistance and DVA output as given below:

NO SPARK OR INTERMITTENT ON ONE CYLINDER:

1.

If the cylinders are only misfiring above an idle, connect an inductive an Tachometer to each cylinder in turn and try to

2.

isolate the problem cylinder. Check the trigger resistance and DVA output as shown below:

Brown/White Eng Gnd Brown/Yellow Eng Gnd

Green/White

White/Green

Green/White

Eng Gnd

White/Green

Eng Gnd

Brown/White

Brown/Yellow

660-710 Open Open 850-1100 Open Open

(*) This reading can be used to determine if a pack has a problem in the triggering circuit. For instance, if you have no fire on one cylinder and the DVA trigger reading for that cylinder is low – disconnect the trigger wire and recheck the DVA output to ground from the trigger wire. If the reading stays low – the trigger is bad.

3.

Check the DVA output on the green wires from the switch box while connected to the ignition coils. Check the reading on the switch box terminal AND on the ignition coil terminal. You should have a reading of at least 150V or more at both places. If the reading is low on one cylinder, disconnect the green wire from the ignition coil for that cylinder and reconnect it to a load resistor. Retest. If the reading is now good, the ignition coil is likely bad. A continued low reading indicates a bad power pack.

WIRE

Read To

Wire Color

Check To (Wire Color)

Resistance

DVA Reading

Brown/White

Brown/Yellow

850-1100

4V minimum connected

Brown/White

Eng Gnd

Open

1V or more (*)

Brown/Yellow

Eng Gnd

Open

1V or more (*)

OEM Ohms

CDI Ohms

DVA

350-450 Open Open 850-1100 Open Open

180V minimum connected None disconnected None disconnected 4V minimum connected None disconnected None disconnected

WILL NOT ACCELERATE BEYOND 3000-4000 RPM:

  • 1.

    Connect an inductive Tachometer to each cylinder in turn and try to isolate the problem. A single cylinder dropping fire will likely be the switch box or ignition coil.

  • 2.

    Connect a DVA meter between the stator’s Green/White wire and White/Green wires. Perform a running test. The DVA voltage should jump up to well over 200V and stabilize. A drop in voltage right before the problem occurs usually indicates a bad stator.

  • 3.

    If both cylinders become intermittent, replace the switch box if the stator tests good.

  • 4.

    Perform a high-speed shutdown and read the spark plugs. Check for water. A crack in the block can cause a miss at high speed when the water pressure gets high, but a normal shutdown will mask the problem.

  • 5.

    Remove the flywheel and check the triggering and charge coil flywheel magnets for cracks or broken magnets.

51

Mercury Troubleshooting

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