Mercruiser Ignition Control Module

[Keith Wilhite]

I've got a problem with my 1996 Mercury 5.7L Thunderbolt V not wanting to fire. With the engine spinning, it seems to initially try and fire, but then won't. Oddly enough, when I toggle the ignition kill switch on & off, it seems to try to make the engine fire each time the switch is in the "on" position. Switch tests okay, so not that. Timing light on plug# 1 lights maybe once when trying to start, then not again. In the Mercruiser manual, under...

"Troubleshooting Thunderbolt V Ignition
Ignition Control Module / Coil / Distributor"

I've successfully made it as far as....

"Unplug WHT/
RED bullet connector
from Distributor.
Check for 12 volts
on lead coming
from module"

I have 0 volts on the lead coming from the mudule with key "on". Manual says replace the ICM. I just wondered if there's any better way to confirm a bad ICM before I purchase a mildly expensive new one. I've read that they normally do not go out unless wet or struck by lightning, neither is the case that I'm aware of. I've actually had this same basic problem for three years. On occasion, after running the engine under a load, it would die when returned to idle. I'd try and re-start and experience the exact same behavior as described above. However, after sitting for about 20 minutes or so it would always start right back up just fine. Won't start at all now. Appreciate any advice available. Thanks!

 

[jerryjerry05]

Re: Mercruiser Ignition Control Module

Check the position of the stall switch.It might be stuck open.Not letting the motor fire.J

 

[Keith Wilhite]

Re: Mercruiser Ignition Control Module

I can't find any information in the manual about a stall switch. Where is that located?

 

[joseph1980]

Re: Mercruiser Ignition Control Module

just a shot in the dark here as i have a different ignition system on my boat but you may want to check your ignition switch. my was bad and was only energizing the ignition module with the full 12 volts intermittently. so sometimes it would start just fine, sometimes not.

 

[Bt Doctur]

Re: Mercruiser Ignition Control Module

Run a test jumper from the battery to the + side of the coil.

 

[Don S]

Re: Mercruiser Ignition Control Module

I can't find any information in the manual about a stall switch. Where is that located?

It's actually called a shift interrupt switch, not a stall switch. It's found in the Alpha I gen II outdrive manual. Of course if you have a Bravo drive, you don't have one at all.
But, if you have made it up to that step in the troubleshooting chart and the previous checks tested out OK, then you don't have a problem with power to your coil, or the shift interrupt system. You need a module.

But, you need to make sure you did the tests before the one you mentioned were all done correctly.

 

[Keith Wilhite]

Re: Mercruiser Ignition Control Module

All initial tests were re-run and it all looks like about the same thing. It does not appear to be a problem with power to the coil. I now have my kill switch wires disconnected from the kill switch. Kind of back to what I was first describing, while spinning the motor over, with the kill switch wires disconnected, I can re-connect the wires and when I do, immediately the motor tries to fire for just a second but doesn't. Does that every time.

 

[thegexbird]

Re: Mercruiser Ignition Control Module

I'm having the exact same problem with my '97 5.7LX. I saw a test procedure online say to test the tach wire in the ICM connector to insure it isn't grounded out. Is this right?

I also don't want to spend a lot of money on a module(that can't be returned, and is a conversion that requires doing some wiring) just to find out my old one isn't bad.

 

[Don S]

Re: Mercruiser Ignition Control Module

You need to start your own thread gexbird.


You must have missed the announcement at the top of this forum. http://forums.iboats.com/announcement.php?f=443