Ignition Problems in Rain

XJ900F has had an issue with misfiring ignition in wet weather, so I have changed the coils, the HT leads and spark plug caps; started the engine and turned on my garden hose and ran water all over top of engine and leads. No misfire great I think, I have cured the problem!................I keep the engine running a short while to dry it off, as it stated to dry and steam rose up under the fuel tank, yes you guessed it it started to misfire. I am going to rewire the loom under the tank to all electrical connections, and water proof grease everything else there. Has anyone else had a similar issue if so how did you resolve it. I will post the results I get after I do the work.

 

Many years ago I experienced misfire on a triple KH250, Major problem occured in wet weather caused by spray from front tire onto engine.

This because I changed front mudguard to a new improved one ( well I thought so at the time!) only resolved it by positioning tax disc holder to stop spray hitting ignition leads.

 

I have thought of that, it seems to be evaporation os water vapour from top engine rather than the soaking itself.

 

That's an unusual one, when you say changed coils do you mean NEW coils?


Have heard these coils can develop a small crack between leads & this may not let the water in until they get the "steam cleaner" treatment?

Good idea to ensure all connectors are clean & tight anyhow, you're on the right track I feel

 

Usually cracked coils are the culprit for wet ignition issues, but since you said you replaced them, that's odd.

Be sure to solder and heat shrink all the new connections for best results.

 

Coils can get "hiarline cracks" VERY hard to see.Had the same problem with my 650 maxim.Where the metal comes out of the plastic body they really like to split there.I sealed mine up with 2 part apoxy never had a problem after that.

 

Thanks for all your comments, yes they are new coils, yes I have soldered all connections and heat shrunk all joints , removed connector blocks and direct soldered all wires. I have only just put it back together I will probably get a chance to test it in the rain next week. I like the idea of two part epoxy over the coils, if the problem continues I will try that next.

 

None of the relays are truly sealed, and there are a few up under the tank. Something could very well be reacting to getting a steam bath coming off the top of the motor.

 

Just realised you haven't mentioned if the misfire is random or if it's always a particular cylinder/cylinders that miss.

If it was a particular cyl, I was going to suggest an easy way to check if it's coil/lead/cap related would be to swap the 1/4 coil connections with 2/3 coil and see if the misfire moves next time it's wet.

 

The misfire was there before I changed (new) coils, leads, caps, I did not know about relay's under the tank!
where are they exactly?

 

Directly under the tank along the backbone(s). You'll need to remove the tank to access them.

 

Thanks I will check them out tomorrow, can't believe I missed them.

 

True, it isn't unknown for new parts to be faulty also though. I think the relays are the sensible thing to jump on next though, but if the miss IS always in the same place don't forget you can prove out the coil etc by swapping :wink: