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Old 07-08-2010, 08:35 PM   #21
Lt. JG
Join Date: Apr 2009
Location: Loch Lomond Scotland
Posts: 31

Changed crankshaft sensor, fuel & power relay all to no avail

Printed wiring diagrams and got stuck in with new multimeter, i have 12v at both the ignition coil and module so the ecm is not telling it to spark, having changed the ecm and most sensors here i have a question

Does anyone know exactly which sensors on the engine will tell the ecm not to alow a spark at the ignition coil??????

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Old 07-12-2010, 01:12 PM   #22
Lt. JG
Join Date: Apr 2009
Location: Loch Lomond Scotland
Posts: 31
Default Fixed - Fixed - Fixed

Finally got this problem licked, cheers for all the inputs and suggestions they all helped and I am now an expert on the Merc 350 mag mpi lol

Traced the fault down to a wonky ignition coil plug, had wiggled the wiring in this area many times trying to replicate the problem before but strangely this time it worked and cut the engine off, half a dozen more times and eureka cut out every time but only if I bent the wires a certain direction and only the pink wire (12v from power relay)

So with the plug being part of the loom and not sold separately I decided to solder 3 wires directly onto the terminals on the coil and then use connectors to the loom wires, all fired up, wiggled away no cut out, sea trials yesterday WOT superb ready to enjoy boating again

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Old 07-12-2010, 01:48 PM   #23

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Sure must be a relief to have sorted that issue - well done!
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Old 07-16-2010, 05:27 PM   #24
Join Date: Jun 2009
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I just had the same problem this week on Lake Chelan. Got towed in by the Lady of the Lake Ferry. Very embarrassing!!! Anyway.... The problem sounds the same. Running fine then dies even while running @ 3500 RPM. I had to replace the ignition control module. $385. This is the 2nd module I have had to replace. Mine is mounted on the exhaust manifold. After talking w/ a local Mechanic, trying to figure out why I had to replace the module again, he told me that the cause had to be heat or some overload in the electrical system. He also told me that if you order an ignition module w/ the wiring harness as a package the instructions say to mount the ignition control module on the hull not the exhaust manifold. So Heat will destroy the module.

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