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Old 06-10-2018, 07:57 PM   #1
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Default Thunderbolt V Ignition losing spark

Hello,
im hoping someone will be able to help me out. I have a maxum 2300sr with a 5.0 mercruiser alpha 1 gen 2. Boat ran great when i winterized it but now the issue is, i have great spark for about 2-3 seconds when cranking then it dies out. I have a spark tester in line with the coil and distributor and see it fade to barely lit. I replaced the coil, cap, rotor, distributor sensor and sill having the same issue. I disconnected the white/red wire from the dist and have 12v. I have gray wire at the tach is showing ground but if i disconnect there is no change. Also should my + and - at the coil be showing 12v? Are there any tests i can perform to diagnose the Ignition control module? Any help would be greatly appreciated.

Thank you in advance!
Chris
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Old 06-10-2018, 08:58 PM   #2
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By replacing the coil, cap, rotor. Yo just norow down to the problem.
Must of the time is the coil what do this things, but you replace that, so the only one left is the Ignition Module.
Wait for some more opinions.
My only suggestion is, if you have to buy a Module, don't buy aftermarket one, they are junks. Quiksilver is o good choice.
Good luck.
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Old 06-10-2018, 10:20 PM   #3
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Originally Posted by Chris H View Post
Hello,
im hoping someone will be able to help me out. I have a maxum 2300sr with a 5.0 mercruiser alpha 1 gen 2. Boat ran great when i winterized it but now the issue is, i have great spark for about 2-3 seconds when cranking then it dies out. I have a spark tester in line with the coil and distributor and see it fade to barely lit. I replaced the coil, cap, rotor, distributor sensor and sill having the same issue. I disconnected the white/red wire from the dist and have 12v. I have gray wire at the tach is showing ground but if i disconnect there is no change. Also should my + and - at the coil be showing 12v? Are there any tests i can perform to diagnose the Ignition control module? Any help would be greatly appreciated.

Thank you in advance!
Chris
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The + terminal on the coil should read 12V to ground and the - terminal should pulse between 2V and 8V approximately.

When you say distributor sensor you are referring to the internal trigger sensor, correct. The newer sensors have three wires instead of two is this what you new one has and did you connect it correctly? If I recall the third wire is connected to ground.
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Old 06-11-2018, 04:26 PM   #4
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The + terminal on the coil should read 12V to ground and the - terminal should pulse between 2V and 8V approximately.

When you say distributor sensor you are referring to the internal trigger sensor, correct. The newer sensors have three wires instead of two is this what you new one has and did you connect it correctly? If I recall the third wire is connected to ground.
Yes, the internal trigger sensor in the distributor has 3 wires. white/red, white/green and black to ground post on engine block. I should also mention i have tach signal while i have spark and no signal when spark dies out. If i stop cranking and try to crank again without turning the key to the off position no spark after the initial drop out. If I turn the key off and then back on again it will spark for a few seconds every time. As for the coil, i have 12v on the + terminal and im about to go check the - terminal for pulsing signal.
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Old 06-11-2018, 06:02 PM   #5
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When you loose spark verify there is 12V on the purple wire on the back of the ignition switch. If no power the ignition switch is bad.
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Old 06-12-2018, 04:53 PM   #6
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When you loose spark verify there is 12V on the purple wire on the back of the ignition switch. If no power the ignition switch is bad.
I have 12v on the purple wire which drops down to 9.5v when cranking. + terminal of coil is 12v, - term is a pulsing signal. I have spark for approx 3 seconds and lose spark and tach signal at the same time. Should have have a pulsing tach signal on the grey wire leaving the ICM? Also if i disconnect the white/green wire from the dist and with the ignition on strike the white/green from the ICM to ground rapidly, i dont see any spark in my spark tester. Im leaning towards a ICM, going by the troubleshooting flowchart for TBV ignition systems i found on this forum.
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Old 06-12-2018, 05:46 PM   #7
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I have 12v on the purple wire which drops down to 9.5v when cranking. + terminal of coil is 12v, - term is a pulsing signal. I have spark for approx 3 seconds and lose spark and tach signal at the same time. Should have have a pulsing tach signal on the grey wire leaving the ICM? Also if i disconnect the white/green wire from the dist and with the ignition on strike the white/green from the ICM to ground rapidly, i dont see any spark in my spark tester. Im leaning towards a ICM, going by the troubleshooting flowchart for TBV ignition systems i found on this forum.
Mike ask you if you have 12V. at the purple wire after you lose the spark.
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Old 06-12-2018, 06:23 PM   #8
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Drops from 12v to 9.5v while cranking and yes i still have it after i lose spark.
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Old 06-12-2018, 09:59 PM   #9
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Well Iím sorry to say but itís seems to be the ICM.
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Old 06-13-2018, 07:40 AM   #10
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Well Iím sorry to say but itís seems to be the ICM.
Thats what im thinking, i appreciate your time and help. I will order an ICM and post again after i replace with new one.
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