1997 Sea Doo SPX Intermittent, no spark/weak spark

[Just Luv Workin on Skis]

Ran great, then after sitting for a break it would crank but not start. Once home checked for spark; sometimes sparks, sometimes doesn’t but never started again. Here’s what I checked.

787 engine. Ignition circuit has: coil directly connected to MPEM and MPEM directly connected to trigger coil; does not have CDI unit or holder relay.

Battery 12.6 volts (will crank for a long time).

Squirted mixed gas directly into cylinders and cranked several times; also squirted directly into airbox (tries to fire once in a while but never starts).

New spark plugs (also tried with old ones) BR8ES.

Compression: Mag side 135 PTO side 140.

All electrical connections are extremely clean in both front and rear electrical boxes (not a hint of corrosion).

Spark plug boots: 5633 and 5164 Ohms. Also tried cranking while holding capless plug wire with safety pin pushed into the end, near to ground (with bare hand); didn’t get any spark that time (getting brave I know).

Ignition coil secondary winding: 13.02 Ohms

Ignition coil primary winding: 0.5/0.6 Ohms

Trigger coil: 251 Ohms.

Put test light on white (hot) lead to ignition coil while cranking; sometimes lights extremely dimly, sometimes not at all. Traced this wire to front electrical box (where it connects to MPEM and repeated the test with the same results (verified good ground of course).

Disconnected trigger coil wiring inside front electrical box (where it connects to MPEM) and placed test light between Yellow/White hot and Black/Yellow ground; cranked, did not illuminate test light. Also tried this with a Voltmeter and shows 0 to 0.2 volts. Then set range to millivolts and meter showed over range error.

I have both the Clymer’s and Sea Doo manuals and neither give much information on troubleshooting; they just say to use the Sea Doo ignition tester, which I don’t have.

This has happened twice before, but those times it re-started after the engine cooled; this time I wasn’t so lucky.

Sorry for being long, but I tried to be thorough.

 

[Just Luv Workin on Skis]

It looks like spark is not my primary issue. If I crank it over with a spark tester in low light conditions it does have spark. It is weak but it does spark. You can't see it in bright daylight. One reason it might be weak is that the manual calls out a resistance of 4,480 Ohms on the spark plug boots and one of mine was 1,153 Ohms higher than that. I can't say why I didn't get a jolt when I tried holding it with a bare hand; maybe I didn't get a good ground.

Anyway, the rotary valve jumped out of timing and this is my primary problem. With the front piston at TDC the rotary valve is completely closed. After disassembly I noticed a very tiny chunk of the edge of the rotary valve was missing and groove was cut into the case and cover on both sides of the valve. I am quite sure I didn't drop anything into the Carbs and the butterfly screws are still in place. Another thread said a wrist pin bearing could have come loose and caused this. It seems impossible for the valve to jump this far out of timing. I am aware that there is a brass gear that drives the valve, and this could have failed, but the rotary shaft turns consistently when I turn the crank.

So please give me some feeback. I kind of hope I am wrong but looks like it is time to junk this thing. It certainly isn't worth a $1,000. rebuilt engine. Should I part it out? Is there a demand for older Ski parts?

 

[TheGTIjetguy]

Hopefully someone with more experience can chime in. My thoughts right now.
If your rotary valve shaft jumped gear teeth there will probably be brass shavings in the case oil in the center sump area where the shaft runs Maybe you can suck it out and see if there is any contamination?
You could always retime the valve and try to run it. Depends how bad the groove in the case is, you have nothing to lose at this point if it works.

If your weak spark issue returns I would be looking at the coil. Your secondary winding reading should be in the thousands of ohms. Something like 9-15 kohms. Primary is ok at .6 but right at the top of the range. .3-.6.
Failing coils often exhibit the symptoms you described. (Works then breaks down internally when gets hot). Always replace with oem denso coil. Amazon coils cause issues.

 

[Babydriver]

I have the same spark issue with my 97 gtx. I bought a mpem and it seems like the spark is still a little weak. Maybe not. Not sure how bright the test should be with a spark tester. My ski has fuel 150 compression on both sides and spark and just couphs a bit when first trying to start it. My head hurts from trying to figure it out

 

[Just Luv Workin on Skis]

Well, as it turns out spark was not the problem at all. In the Florida sun it is terribly hard or even impossible to see spark. The spark can be seen only when the sun is very low in the sky or at night. Even in low light, it seems to be a weaker spark than anything else I have ever worked on. However, I found the real problem, a sheared Rotary Gear. Since this is unrelated to spark I am going to start a new thread describing what I found with the Rotary Shaft and Brass Gear.