1999 XP Limited Fueling Issue

[SeaDooDoo90]

Got the siphon tubes installed yesterday which fixed the elbows pissing inside the hull.

Now, I think I have an electrical issue. The ski is running worse than it ever has, and now has a hard time cruising above even 3500 RPM. Yesterday, it was able to sustain ~5000 RPM for a quarter mile before it started bogging down badly. At one point, I opened the throttle completely and it held constantly at about 3500 RPM. Shortly after, the engine died on me. I got it started again without much effort and limped back to the trailer at about 2k RPM, where it runes fine without issue. When I attempted to restart it on the trailer in the water to move the ski to the front of the bunks, the starter was completely dead. The solenoid would consistently click, but the starter made zero sound. This is a first.

The plugs still look great, so I don't think it's starving for fuel and risking a lean condition. In my experience, fueling issues can often be "overcome" with some creative throttle feathering (so long as the fuel supply is sufficient, which I've confirmed mine is). It makes for suboptimal riding, but is doable. This ski acts differently though. No combination of throttle voodoo is of help, and it runs worse the longer it stays out on the water.

I now fear my MPEM is on its way out, likely from the hundreds of gallons of water that have collectively entered the hull thanks to the missing siphon tubes. I was just reading through the 1999 shop manual on how to function test the MPEM with an ohm meter, and it only lists a procedure for the GTS. It says for all other models "It is not possible to accurately check the MPEM condition without specialized tools. Therefore, replace MPEM with a good known unit to conduct testing."

Is this really true? There's no way way test this on a '99 XP???

 

[FL-Rider]

If you think its electrical, you could check the ground strap connection on the front of the motor. I would also check the negative battery cable connections at the starter and battery. You could unplug your harness connections and use a bright flashlight to look at the pins and sockets. If you want to check spark strength, you can get an Echo PET-4000 spark checker. Since I wouldn't know how or have the equipment to check the MPEM, I would use my time to go back through the carbs. Even if you think the aftermarket parts are good, its possible something is failing the pressure test, like needle seat orings, the needle & seat set, the arm angle for the needle might be bent out of adjustment, clogged passageway, bad check valve, etc. Also, some of those aftermarket diaphragms have thicker center buttons than original and in my opinion could throw off the calibration of the fuel delivery.

 

[SeaDooDoo90]

If you think its electrical, you could check the ground strap connection on the front of the motor. I would also check the negative battery cable connections at the starter and battery. You could unplug your harness connections and use a bright flashlight to look at the pins and sockets. If you want to check spark strength, you can get an Echo PET-4000 spark checker. Since I wouldn't know how or have the equipment to check the MPEM, I would use my time to go back through the carbs. Even if you think the aftermarket parts are good, its possible something is failing the pressure test, like needle seat orings, the needle & seat set, the arm angle for the needle might be bent out of adjustment, clogged passageway, bad check valve, etc. Also, some of those aftermarket diaphragms have thicker center buttons than original and in my opinion could throw off the calibration of the fuel delivery.

Finally getting around to verifying wiring connections I should have done long ago.

I followed the ground wire from the battery and to my surprise it terminates at the e-box and not the block. Where is this ground strap you speak of at the front of the motor? I have the airbox removed for easier access, but no other parts ATM.

The more I think about it, the more a bad wiring connection makes sense. I think you're onto something with your suggestion. Over the summer, my main ground failed on my '97 SPX. It acted not identically, but somewhat similarly, before the ring terminal completely broke and the ski was dead in the water.

 

[FL-Rider]

Mine is a 98 xpl so it might be different. On mine there is a ground strap (approx 14 guage wire) that is connected to the engine by one of the front magneto cover bolts. My negative battery cable bolts to the starter housing.

 

[SeaDooDoo90]

Ok, finally got around to doing some further investigation.

First, disregard my prior post to this about the ground cable terminating at the E-box. It does indeed connect to the bottom of the block from the battery.

I unscrewed it at the block to check the condition of the ground terminal. It was extremely oily, pretty much completely covered. In its current state, I did a continuity test of the cable with one lead on the battery terminal end and the other the block end. On the block end, the continuity was intermittent at times, depending on exactly where the probe was positioned on the terminal. I would move the probe around the ID of the ring and on both sides of the terminal, and was never able to get a constant beep for more than a few seconds. I also tested the battery side terminal, which I thoroughly cleaned last season, and it didn't skip a beat - perfect continuity.

So, I thoroughly cleaned and took some sandpaper to the block side terminal. Tested continuity again and this time, it was constant just like the battery-side terminal.

I am hopeful I'm onto something here. I'll report back once I have the ski back together and can take it for a test ride.