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I've been trying to find the cause of power loss. Loss of power through out rpm range and tops at 4100 rpm. After new plugs show lower left cylinder oiling up I put a new ignition coil on that cylinder. When taking it out for a run, I accidently left the right side plug caps off and it reluctantly started. However, it was noticeable I had strong spark on the two right mid and lower cylinders when I put them back on. Seems like nothing on top right. While removing top right coil there seemed to be corrosion and oil leak coming past the plug. Two questions. Could the engine start on just 2 cylinders? Can the loss of just 1 cylinder drop the top rpm over 1000 rpm. Any help would be appreciated. I'm taking it back out now to see if there's more power, but I'm far from getting it to run at the 5600 rpm it ran at earlier this year...I'm hoping not to replace another coil....maybe just a grounding problem.
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In answer to your two questions. Would that engine start on two cylinders? - probably not. Would it run at those lower revs with a cylinder not firing? - yes depending on load.
Marginally faulty ignition coils (includes poor earthing) predominately make starting difficult but once engine starts, can show little performance difference and only shows up under extreme load conditions such as pulling out a waterskier etc. Keep checking earthing. but faulty coils can be detected by moving them to known working cylinder and see if engine starting /running suffers (primary lead needs to be also reconnected not just HT lead!). Faulty coils can also be diagnosed by the resistance readings with a multimeter. Even marginal ohm reading differences can indicate a faulty coil. I took a coil that I suspected faulty (a very little detectably off it's siblings) to a shop that had a machine setup to test it sparking; they swore it was OK - they do this all the time - but I decided to part with bucks for a new one. It solved the starting difficulty I had (the coil was faulty). -
Testing things is a lot better on pocket book than throwing parts at a motorComment
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