No ignition when warm engine, 1990 2-stroke Tohatsu/Nissan 18 hp

[Rick_n]

Any idea what is the problem? My old 18hp Tohatsu starts well, operates well for a while but then when the engine is warm it starts misbehaving and shuts down and will not start again, gives no ignition. After waiting for an hour, it starts with first pull (without choke). Is it a CDI box problem?

 

[pvanv]

Could be. Test the electric components when failing hot.

 

[Sea Rider]

Welcome to Iboats,

Odds are having an electric failure due to electrical components which are 3 heating up and shorting and working normally back again when cold or you have a cylinder gasket failure which lets water droplets in and engine misses badly, even shuts down when KO until cylinder head cools back and "seals" combustion chamber again. Head gaskets don't lasts a lifetime and yours is a 25 year oldie head gasket. Who is the culprit, it's an electrical or mechanical flaw, that's the issue...

Happy Boating

 

[Rick_n]

Thank You for your replys. I have downloaded the service manual and will probably perform the ignition tests first.

 

[gm280]

You can help whittle down the possibilities with a little effort on your part. When it starts acting up and shuts down. Check to see if you have spark. If so, then it isn't any electrical issue and look towards mechanical. However, I'd bet it will not have spark. And then you can work back towards the ignition module. If spark is not on any cylinder, it isn't the spark plug coils. Well at least not the number one suspect anyway. Because the probability of all the spark plug coils stop working at the exact same time is questionable....but not impossible either. But I would then check the ignition module... Just a process of elimination. JMHO!

 

[Rick_n]

Back to this issue. I changed the CDI box. It was very easy job to do. Now the engine works fine!! No matter if it is cold or hot. Box was available here:

http://www.lowcostboatingstore.com/CDI-119-0602-Tohatsu-Nissan-Ignition-Module--2-Cyl_p_37791.html

 

[Sea Rider]

Yep, if one plug doesn't fire, it's a Ignition Coil issue as it's a siamese coil pack. If both plugs don't fire it's a CD related issue. That's a typical failure, electrical componenst heats, shorts whatever and misses, when cools down engine starts again to miss and so on..

Happy Boating