High resistance in Secondary Winding on Ignition Coil

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Cronullalad

Cronullalad

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Hi all,
I have a 1998 Seadoo Challenger 1800 where the port engine has recently chosen to run on one cylinder once warmed up. In checking the resistance on the secondary windings of the Ignition Coil (spark plug caps removed) my meter registered 20.5k oms but the manual suggests the reading should be between 8.4 ~ 15.6k oms. Does this higher that expected reading indicate that the coil is malfunctioning ???
Any help on this would be greatly appreciated.
 
Correct, 2 engines and two separate coils. Have swapped the coils over and have the same result.
Have this morning installed the test harness and static tested Trigger Coil....should be between 190~300 ohms....mine is 259 ohms.....so should be ok, Then checked the good engine just for a comparision, it reads 255 ohms .
Then did Dynamic test for Trigger Coil on bad engine.....should read between 0.2~0.5Vac.....my reading was 0.8Vac, Checked good engine and also read 0.8Vac.
Primary winding on the Ignition coil should be approx 0.6 ohms, mine is between 0.7~0.8 ohms.
Really confused now....the readings are not that far out and it does run ok when cold but after a minute or so one cylinder starts to miss.
Any further ideas ???
 
I didn't want to do any damage.....its not really very happy running on one cylinder.
Will give it ago tomorrow.....hot !!
Thanks
 
Could it be that the insulation becomes less with increased temperature? When you say hot, do you refer to the engine or the coil. I would compare the coil temps of both engine simultaneously, if you have only an IR probe, or even better take a thermography if you get your hands on a FLIR. If you have some damage in the coil, it should show up as temperature?
My offer to borrow one of my coils is still on the table, I won't get my 787's together for another few month.
 
The way I was looking at it is you're out of spec but running on 2 cyl then it warms up drops to one cyl and you see how far out of spec you are then to narrow it down to the coil
 
The engine goes down to running on one cylinder when the engine warms up.
Will re test tomorrow with the engine warmed up.
Thanks again gfk for the offer......have used both my current coils on this engine and the other good one.....both coils appear to be good.
 
intermittent ignition issues are quite commonly affected by heat, if the symptoms only happen when it is hot then that is when you need to test it. Don't forget to check the resistance of the spark plug caps also, I have seen them go bad also.
the easiest thing to do first is put an marine quality inline spark tester on the engine that is running on one cylinder, then you can see if both cylinders are getting spark or not, if you find one cylinder isn't getting spark and the other is then the problem is definitely in the ignition coil, wires or caps. if you find both are still getting spark when running on one cylinder then you know to start looking at something else.
 
Also keep in mind that these coils fire both plugs at the same time so if one isn’t getting spark it has to be the wire or cap. If you switched the entire other good coil and wires it’s not a spark issue.
Are these engines twin carb? What’s the compression on each cylinder?
 
Hi Wrench, caps all test OK at 9k ohms. Have put an inline tester on both engines.....but the port engine starts OK, then you can see one cylinder with erratic spark. How can spark from the coil divide to limit one cylinder.....this morning I trimmed the spark plug leads on both ignition packs and reinstalled the caps....the connected caps show a solid a resistance / circuit.
Hi mikidymac, Both engines are twin carb.....are the plug wires twisted into the coil similar to the caps ??
 
that is pretty odd...at what rpm is the problem happening??

the secondary winding from the ignition coil is connected together so for it to be a problem with a specific coil you would have a problem on one wire or cap or the connection of the wire, yes the wire attaches the same way to the coil as it does the caps. so since your problem is the same with both coils I would think the issue has to be after the coil, the spark has to complete a path to ground so you would have to consider the condition of the spark plug itself and the ground connection the spark plug makes to the head and its connection to ground through the cylinder and crankcase and then of course to the ground wire itself and back to the coil and ecm.
 
Cronullalad said:
Hi Wrench, caps all test OK at 9k ohms. Have put an inline tester on both engines.....but the port engine starts OK, then you can see one cylinder with erratic spark. How can spark from the coil divide to limit one cylinder.....this morning I trimmed the spark plug leads on both ignition packs and reinstalled the caps....the connected caps show a solid a resistance / circuit.
Hi mikidymac, Both engines are twin carb.....are the plug wires twisted into the coil similar to the caps ??
Click to expand...

Is your ohm meter accurate? The plug caps are 5k ohms each, not 9k.

Chester
 
Hi Chester, Thanks...I just rechecked the manual, it suggests the caps have 10 ohm resistance, I guess there are different brands out there that will have different resistances. To my knowledge my meter is accurate.
 
Hi all, seems like the problem might have been the plug wire and cap connection joint.......since reseating both joints on both ignition coils, things seem to have settled down. The "bad" engine revs from 1500 up to and holds at 3000 ~ 3500 rpm without a problem.....then the next problem kicks in....transition from low to high speed throttle. When pushing through to 7000 rpm both engines work well for 5 to 6 seconds then appear to starve for fuel ???. The revs completely drop off at 7000 by about 750 revs then regain 500 revs and continue this overall reduction to about 3000 revs where they appear to run smooth. Tested each engine independently with the other engine off to determine this.
Looks like there may have been a spark issue plus a fuel issue. Will try again next week end and see what the fuel issue is or what other surprises there are.
 
Cronullalad said:
Hi all, seems like the problem might have been the plug wire and cap connection joint.......since reseating both joints on both ignition coils, things seem to have settled down. The "bad" engine revs from 1500 up to and holds at 3000 ~ 3500 rpm without a problem.....then the next problem kicks in....transition from low to high speed throttle. When pushing through to 7000 rpm both engines work well for 5 to 6 seconds then appear to starve for fuel ???. The revs completely drop off at 7000 by about 750 revs then regain 500 revs and continue this overall reduction to about 3000 revs where they appear to run smooth. Tested each engine independently with the other engine off to determine this.
Looks like there may have been a spark issue plus a fuel issue. Will try again next week end and see what the fuel issue is or what other surprises there are.
Click to expand...

Does it seem like it’s hitting a rev limiter? Make sure it isn’t overcharging, if the charging voltage gets to high it will put itself in a protection mode and activate the rev limiter
 
Hi Wrench,
Thanks for that info. Will check on the weekend.
I did have another thought, I'm wondering if the fuel tank breather is blocked or severely restricted...reason is late yesterday I was flushing the engines and both worked perfectly....no sign of a fuel issue. Again will have to want till the weekend to check.
 
The fuel valves are known to clog easy and can starve a motor to a lean melt down. They are easy to bypass and test with some 1/4 fuel hose
 
Cronullalad said:
Hi Wrench,
Thanks for that info. Will check on the weekend.
I did have another thought, I'm wondering if the fuel tank breather is blocked or severely restricted...reason is late yesterday I was flushing the engines and both worked perfectly....no sign of a fuel issue. Again will have to want till the weekend to check.
Click to expand...

ok, make sure you check the voltage when it is acting up. you could have a venting or restriction issue but it sounds more like a voltage issue to me with what you described before. when it is acting up make sure it isn't over 14.7 volts, also make sure you are running resistor spark plugs, non resistor plugs can cause all kinds of problems also. if that stuff checks out you will have to start going through the fuel system.
 
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