Merc IO 140 4cyl. no spark


Old 07-04-02, 07:24 PM
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Unhappy Merc IO 140 4cyl. no spark

I have a 1986 Merc 140 3.0 I am perplexed with lack of spark. I have voltage at the coil of about 12.4 volts both at neg and positive posts. No spark from coil wire or plugs when pulled out and connected to wire. My neutural switch is bad but tied the wires together for temporary fix but now can not get spark. The points are opening and closing , any ideas?
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Old 07-05-02, 12:12 PM
telco tech
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Disconnect the two 12volt coil wires, place a 12volt test light across these, crank the engine. The light should pulse as the points open and close. If not the condenser maybe shorted, and the points can't send pulses to the coil. Most meters won't due for this test, they don't respond quick enough, you might be able to use an analog meter for this. Also an opened or shorted coil maybe to blame, it's hard to test a coil with a meter though, unless the coil is completely open. A coil can measure good on a meter, but be arcing inside when it develops high voltage. A bad condenser can also cause a very weak spark.
Old 07-07-02, 11:24 AM
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After changing the points and condensor $13 my engine fired! Thanks.

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