No spark???

[citadel1995]

1992 merc 25 hp was running great & just died. Motor turns got fuel but no spark. Fuse is ok! What can it be?
Thanks

 

[citadel1995]

Re: No spark???

Ok so I got towed back to landing got home and motor fired up. So I let run for about 5 min and it died again. No spark again. How do I troubleshoot this? What could be the problem?

 

[aussieflash]

Re: No spark???

Start elimination process.Plug,coil,stator/trigger,switch box.There are tests you can do before running out and buying stuff.Procedures will be listed in your manual.

 

[ronsealdeath]

Re: No spark???

I just had a spark issue, I'm a relative newbie and a bit clueless so ran around like a headless chicken taking off flywheels, stators etc... In the end it turned out to be a simple issue, the kill switch was faulty and grounding out. So I would check this first. Get a manual, check the wiring diagram and see where to disconnect it from your switchbox. Mine was blk/yel. My engine fired up straight away after I did this compared to little/no spark before. I just need to find the fault in that circuit now which shouldn't be too expensive to fix!
Good luck and just try and follow the manual.
Al

 

[citadel1995]

Re: No spark???

Thanks for the insights so far. I have checked the ohms and the stator was within specs for the Black/yellow (Low Speed) but the Black/White (High speed) read 140 and specs indicate 200-300. Is this difference major?
The trigger measured within specs for ohms. I still need to do the DVA tests but need to go find one or make one. I have printed out the plans on how to make one so I hope to be able and find all the parts today. Kill switch is OK. New plugs. Ignition coils were all within specs for resistance. I'm feeling like it's going to be the stator, Im going to pull the flywheel here this afternoon as well and check for any noticeable issues there.

 

[citadel1995]

Re: No spark???

So I checked the wires in control box and discovered a loose crimped connector for the ground so I repaired it and checked all other connections. kill switch works fine and the key switch works fine. I put it all back together and she fired up and ran for a couple minutes then died. Back to the same problem, No Spark. I got my DVA and started testing. the trigger was within specs, wire to wire 9.8v and wire to ground 1.2 - 2v. The Stator was well below specs on Low Speed (Black/Yellow) to Ground was 12v, per specs it should be 180v +, and High Speed (Black/White) 25v and per specs it should be 25v +.

Now my question is am I correct in concluding I need to replace the stator?

Would that loose ground connection have caused the stator to go bad or is there anything else I need to check so that the new stator does not get destroyed when installed. I tried to DVA test the coils but got nothing, I'm assuming that is because of the bad stator.

Thanks for the help before I go spend money on a new stator.

 

[NYboater1969]

Re: No spark???

Does your motor have a switch box? These can malfunction when hot and kill spark. It seems that if your stator is good but no power at coils, then it is something in between.

 

[citadel1995]

Re: No spark???

yes there's a switchbox. but after testing the stator with DVA and only getting 12v instead of the required 180v I am planning on replacing the stator, even though the ohms test was ok. From everything I have read if it fails the DVA it needs replaced, even though the resistance test was within specs. I am wanting confirmation on my way of thinking!

Also, I was wanting to know how can I test the switchbox if the stator is not good? I have been looking around for any information on this but everything I have read says there's no real way to test the switchbox, except by eliminating everything else. I also have read several times that whenever the stator is replaced the switchbox should be replaced as well. Is this true? Do I need to buy a new switchbox in addition to the stator or will it be ok to connect the new stator. If the switchbox is bad will it hurt the new stator?

 

[Kyle C]

Re: No spark???

If you find that the stator is the problem you should replace the trigger as well. A new stator can burn an old trigger. Plus, you've already got the flywheel off.

 

[NYboater1969]

Re: No spark???

The first thing to do is search the 'sticky' posts at the top of the Merc forum for the link to the factory service manuals available for free download.
Second is download the free Ignition Troubleshooting Guide from the Support page of CDIElectronics.com
Their excellent guide will walk you through all the tests necessary to determine what part(s) are at fault. This includes testing the switchbox.
A few months ago I was able to fix my Merc 135 hp V6 using these steps, although I had no marine engine experience. Going through these steps saved me a BUNCH of money.