Merc 5.0 alpha 1 gen 2 thunderbolt 5 - no spark (2003 crownline 202)

Badtbone

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Hi

Memorial Day weekend I opened the boat from winter. Started right away and I ran it on muffs for about 45 min as I cleaned it up.
Next day started on first try. Put it in the lake started right up again. Left dock and after cruising for abou 5 min I stopped the boat to check on things. Gave it gas to continue on and it died. Couldn't get it to start again and had to call a friend to tow me in.
The engine turns but doesn't start.
In driveway I used a spark tester and no spark
I disconnected the shift interrupt or and connected the 2 wires to eachother bypassing the switch - no spark
Tested + terminal on coil/purple wire - 12v
Disconnected tac - no spark
Replaced cap rotor and sensor - no spark
Diconnected red/white wire to distributor - 12v
Couldn't get spark from coil while tapping green/white wire
I know this is leading to the ICM but is there anything I may be missing that could cause no spark?
It was running great until it died.

Thanks in advance...
 

Fun Times

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Couldn't get spark from coil while tapping green/white wire
I know this is leading to the ICM but is there anything I may be missing that could cause no spark?Thanks in advance...
Possibly the coil has gone bad internally causing a no spark situation.

Is the engine carbureted?

Take your standard test light and connect to Battery 12+ volt and touch the - side of the coil and crank engine over with the ignition key. Test light should flash/blink.

If it blinks and no spark should = bad coil. No blink may mean a problem with ICM, ICM wire harness or sensor under the cap.

Good luck.:usa::usa2:
 
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Badtbone

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Test light broken- my son swears he didn't touch it....
I will pick a new one up tonight
Thanks
 

achris

More fish than mountain goat
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Badtbone;n9976800...I disconnected the shift interrupt or and [b said:
connected the 2 wires to each other[/b] bypassing the switch - no spark...

And that will stop any sparks whatsoever.

When you disconnect the switch, isolate the wires. Connecting them is what shuts spark off.... (and you only need disconnect the white/green.)

Chris...
 

Badtbone

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Wait - so to bypas the switch I just disconnect the two wires from the switch?

Would I still get 12v at the coil and the distributor but no spark?

Thanks
T
 
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Badtbone

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Does the gray wire need to be connected to coil? I have a purple wire on + side And grey on - side. To test a new coil can I just use the purple wire?

I'm still confused about how to bypass the shift interrupter switch.

Thanks and happy 4th!
 

Badtbone

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I found this - and based on the advise from Chris I assume its incorrect .

3. Bypass the shift interrupter switch by disconnecting wires at the shift
interrupt switch.
Temporarily join the engine harness wires together ( the wires you unplugged
from the switch).

IMPORTANT: Do not fail to reconnect these two wires to the shift interrupt
switch when timing
procedures are complete.
 

Fun Times

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Does the gray wire need to be connected to coil? I have a purple wire on + side And grey on - side. To test a new coil can I just use the purple wire?
Believe you should have 2 gray wires. One going into the wiring harness to the main wire cannon plug heading to the tachometer and the other going to the ICM mounted on the port exhaust. You need the one to the ICM connected to start the engine. The gray wire going to the RPM gauge should be disconnected for a test to see if it's a problem.

I'm still confused about how to bypass the shift interrupter switch.!
I found this - and based on the advise from Chris I assume its incorrect .
3. Bypass the shift interrupter switch by disconnecting wires at the shift
interrupt switch.
Temporarily join the engine harness wires together ( the wires you unplugged
from the switch).

IMPORTANT: Do not fail to reconnect these two wires to the shift interrupt
switch when timing
procedures are complete.
The info you found is for a 3.0 4 cylinder engine and that's to set ignition timing...Your title says 5.0l V8? They are different procedures.

Please post your engine serial number so we can try to help you better. Thanks.:usa:
 
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achris

More fish than mountain goat
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27,468
I found this - and based on the advise from Chris I assume its incorrect .

3. Bypass the shift interrupter switch by disconnecting wires at the shift
interrupt switch.
Temporarily join the engine harness wires together ( the wires you unplugged
from the switch).


IMPORTANT: Do not fail to reconnect these two wires to the shift interrupt
switch when timing
procedures are complete.

This is for a 3 litre engine with an EST ignition system.You have a 5 litre engine with Thunderbolt V (at least that's what the title says)... Complete different systems... Joining the interrupt switch wires on a TB-V WILL stop all sparks....

Chris.......
 
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Badtbone

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Thanks for clearing that up. I reconnected the interupter switch then disconnected the white striped wire. It started. Then I reconnected bothe wires and it started. Then I reconnected original coil and it started. Took it to the lake tested shifting runs great.
So I'm still not totals sure what the original problem was. I replaced cap, rotor and sensor but I feel like it was something to do with the interupter switch.

First time out on Memorial Day after 5 min came to a stop then gave it gas and it died... Chris - thanks for the wiring info. I had it wrong while I was testing. I did try reconnecting it before and no luck. At some time in the process I fixed something or something fixed itself.

Is there any other testing I should do to make sure it's actually fixed so I can enjoy the lake with confidence?

Thanks for the help.
T
 

achris

More fish than mountain goat
Joined
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Messages
27,468
...Is there any other testing I should do to make sure it's actually fixed so I can enjoy the lake with confidence?...

Not really. Just ensure the wires are clean and the connections tight, that includes BOTH terminals on the battery and the leads (again both, red and black) on the engine... So many people forget the ground is just as important as the positive lead....

Chris........
 
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