Seadoo Challenger no Fire in one cylinder

[danzr1]

Hi Guys,

My friend bought a 1997 Seadoo Challenger with the 800's. One engine doesn't seem to fire on one cylinder. I have swapped the spark plug cables and the same cylinder seems to fire just fine, one doesn't. Swapping cables eliminates the bad spark plug cable. I can tell because the spark plug in one cylinder is warm/hot, on the other isn't getting hot. Also, just looking at the plug, its looks clean and new, where the one firing is browning.

We are aware the compression is low. 120 no fire, and 125 in the PTO side. It definately needs a top end. Would it still not ignite that cylinder with low compression? We get about 4500 rpm on that engine.

 

[2x2smoke]

Maybe a mod will move the thread for you over to boats


If its a spark or compression issue, the plug should have unburned gas on it. probably a problem with the carb on that side. You could squirt some fuel into that throat while its running to see if the cylinder responds. Use a tiny bottle and have a big fire extinguisher on hand.

I'm not sure at what psi a cylinder will fail to ignite from poor compression but I'd guess its less than 120

 

[danzr1]

Well my friend told me the weak compression was actually on the engine that ran fine. The one not running right has 140/135 psi. Carbs are off for a cleaning now. Its pretty filthy in there. I'll update once they back in the boat.