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RFI Fouling Plugs

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ranga97

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Hey guys,
Last weekend I took out the ski and all was well for the first hour, then in the second I fouled the PTO plug, it would go then if I pumped the throttle a little it would clear a little then go again. Went in and replaced that one, then going back out it would stumble to get up to the usual 6900RPM but all was well after about a minute, then 15 minutes later it fouled again.
Any idea on what could be causing this?
I believe its fuel fouled, black but the fuel evaporated off when I pulled it
Cheers guys
 
Spark issues won't "Foul" the plug. So... if there was no spark... nothing in the combustion chamber would burn... so when you pull the plug, it would be clean. (but wet)

If you suspect a spark issue of some kind... then put in a fresh set of spark plugs, and go for a ride. If one plug is dead... you will have very little power, and it will be immediate even on the new plugs. BUT, if you put in fresh plugs, and it runs well for a while... then eventually, it starts dropping a cyl (as the plugs foul)... then it's fuel.


The leaking injectors are becoming a very common issue, now that the RFI skis are becoming older.
 
2 freshies bought, how'd your replacement go? [MENTION=77639]Drunkenaviator[/MENTION]

Dirt simple, all you have to do is unplug the wires, undo the two 10mm screws, and the whole rail comes right out. Pop the old ones off, put the clips on the new ones, and they go right back in the same way. Takes 20 min, if that. Hopefully it helps yours more than it did mine!
 
Well - the injectors seemed to be the fix! Hooray!
But now a new problem has risen!
Anyone know what could cause a sticky rpm region? It's either 4100 or 4800rpm, nothing in between. I'll make a new thread for that...
 
Spoke too soon, any ideas on what I could try next?
It's as if the rear spark is just too weak, but it seems to only happen after the ski has gotten hot, I think I'll try using a BR7ES instead of an 8 in the rear cylinder. The front cylinder runs fine, the ski idles normally, just as soon as you apply throttle it doesnt go past 4500rpm and only is running on the front cylinder.
 
compression isn't the problem then, try removing the spark plug boots and clipping the wires 1/4" and try again, the plug wire can get corroded and cause spark issues. process of elimination.
 
there are many things that can cause the spark plug to be wet with fuel such as bad tps sensor or need to be reset if removed, bad coil, tps sensor and air pressure sensor plugs crossed, fuel injector plugs crossed or pto fuel injector and rave solenoid plugs crossed, a bad air pressure sensor, or bad mpem. mpem meaning not putting out enough volts to the coil to fire correctly i would highly recommend googling and shop manual or become a premium member here so you ca download the manual as it has the test procedures to ohm out all the fuel system sensors and had wire color codes for the sensors. the tps and air pressure sensors have the same 3 prong plugs and can be mixed up so color coding would help see if yours may be mixed up. also the rave solinoid and fuel injectors have the same plug type. again color coding the wires will help determine if yours are in the correct spot.
i just got rid of a gsx rfi that i completely rebuild and triple checked everything. after 1 1/2 seasons i decided i had enough and traded it in on a new ski. a month later, i spoke to someone in another forum that specializes in seadoo repair whom followed my post and said that he swore he had a customer that had my ski as he had the same issues, he finally tried a spare mpem which solved the issue! it had to do with the mpem not sending enough volts to the coil. the only thing i did not try. this guy had 2 rfi's in a row with the same mpem issue! not necessarily saying that is your issue. i hope you can get to the bottom of this. my rfi ran great on the lake once started but after it warmed up it would no start and fuel foul the plugs. keep us posted how it goes.
 
Thanks Jammin777, so I just tested the resistance of the primary side of the coils, and they are both in spec (0.4Ω/0.4Ω), the manual states the secondary side is untestable so next time I'll test the voltage supplied to the coil by the mpem. Anything else I could check while the coil is out?

Edit: I also recently trimmed the plug wires in an attempt to fix it, but no fix.. rats
 
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Isn't there two coils? Could you swap them to see if the problem moves ?
Also when you measure the A/C going to the bad side, compare that to the good side.
I think you can also trim the eires inside the coil too.
 
On an RFI the two coils are sealed inside a box, so I can't swap them around, or trim the wires there
 
Okay, so I took it for a quick look over by a mechanic, and he believes it to be the crankshaft not being able to push the piston right to the top under load, but without a load it will show normal compression. Would this sound correct? Therefore I'm up for a rebuild. The ski's got 200hours on it now and never been rebuilt before.
What do you guys think?
 
???? the crank just holds every thing together, it take compression,spark, fuel and air to make it all happen. if one of those is weak, then it will not run properly. you say you have 145 140 psi compression, that is not too terrible. have you tried with a well know working compression tester? i never heard of testing compression under load! i doubt that you need a new engine rebuild just yet unless the compression reading is off, no load needed! both plugs out, wires on grounding post, wot with a good battey.
spark plugs still getting wet with fuel? it is fuel or weak spark related.

how fresh is the gas?

maybe bad tsp or needs calibrating? not calibrated can throw the fuel mapping off = too much fuel or little. tps can only be thrown out of calibration if it has been removed from the throttle body. a bad air pressure sensor can also cause issues. i heard if it ever gets wet is is deemed bad. which also messes with the fuel mapping.
did you download a service manual to check for color coding on the wires to the plugs that go to the tps and air pressure sensors? those two can be accidentally swapped as they share the same plugs.
same with rave solenoid and fuel injectors.
speaking of rave valves, have you checked them for cleanliness? rave bellows for leaks?

now for spark. pull the crank position sensor and see if there are any metal shavings. could be coil or mpem? there is really no way to check the coil or mpem without the right equipment unless you have donor parts to swap. but one thing you can do is check all the connectors and amp connections at the mpem for corrosion or bent pins.

one thing you might do is check the rotary valve for clearance and timing and while you have the cover off see if there's any slop/play by trying to turn the rotary valve back and forth.

also check battery voltage while running at 3 k rpm, should be around 13.2 14 volts. if closer to 15 volts, can cause weird things to happen. the cause would be bad rectifier.
check all your ground connections. from battery to starter, from starter to mag housing, there should be 2 ground wires from a harness to the top of the mag cover. make sure they are clean and secured.
about 90% of these things can be checked for little time and free. i highly recommend downloading a repair manual as it will guide you how to check everything. good luck and keep us posted.
 
no problem, ive been there and checked everything but the mpem wife would not allow 500$$ for it to and take a chance. rather than let me buy a new ski instead! lol. she knew how much it meant to me to enjoy the sport again but hated wasting money on the gsx as i already had tons of $$ in it.
hope you find the solution.
 
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