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.

 

[SeaDooDoo90]

Took the ski for a test ride and no improvement. Couldn't have hurt to clean those connections though, the bottom ground strap was very oily.

I tested my ignition coils again with a multimeter. I put one probe to each coil and my reading was 0.8 ohm.

Does this mean it's as simple as bad ignition coils? The shop manual states it should be in the following range:

 

[Widowmaker2011]

Sorry to pop in “mid-thread”…. But here is my 2 cents … I currently own 2 museum quality XPL’s , a 98 and a 2000 (both with under 10 hours total use in 25 years) and used to race 2 other XPL’s in endurance racing for many years .


You definitely do not have an electrical issue . Let’s put that to bed .

Your XPL was lean in the mid range which is indicative of air in the system or a multitude of other causes that will starve the motor for fuel ….. one thing I have not seen mentioned here is your carb pop off pressure …. Should be between 19-23 psi. If that has not been checked start there …. And the Venym kits are ALWAYS suspect ….they are not even in the same class as Mikuni , there are small almost indistinguishable differences in fit and that’s an issue when dealing with tolerances as tight as moving internal carb parts .

Ok so now into the bad news. What you’re describing now is indicative of water ingestion/ damage . Your friend mentioned taking some water over the bow …… , the 951 is notorious for inhaling water ( especially if the rubber water diverter flaps were never installed or removed at some point ) . It should be noted the water spraying out of your junction elbows can also wreak havoc with the 951 as it’s sucked in to the motor… But back to your current issue . Water in the air box means your motor did inject some water . On the 951 , gulping water usually doesn’t hydro lock the motor , it merely washes the cylinders ( cold water takes the place of the hot gas oil mixture between the piston and cylinder wall ) which chews the piston up and creates friction and puts deep grooves in the cylinder.

Motor will run but will exhibit the exact symptoms you describe .

Recheck your compression and let us know what it is now.
Good Luck -
WMaker

 

[2strokeboy]

I had the same problem with a 2000 gtx, same engine. Didn't work unit full genuine mikini carb kits were installed.

 

[SeaDooDoo90]

Sorry to pop in “mid-thread”…. But here is my 2 cents … I currently own 2 museum quality XPL’s , a 98 and a 2000 (both with under 10 hours total use in 25 years) and used to race 2 other XPL’s in endurance racing for many years .


You definitely do not have an electrical issue . Let’s put that to bed .

Your XPL was lean in the mid range which is indicative of air in the system or a multitude of other causes that will starve the motor for fuel ….. one thing I have not seen mentioned here is your carb pop off pressure …. Should be between 19-23 psi. If that has not been checked start there …. And the Venym kits are ALWAYS suspect ….they are not even in the same class as Mikuni , there are small almost indistinguishable differences in fit and that’s an issue when dealing with tolerances as tight as moving internal carb parts .

Ok so now into the bad news. What you’re describing now is indicative of water ingestion/ damage . Your friend mentioned taking some water over the bow …… , the 951 is notorious for inhaling water ( especially if the rubber water diverter flaps were never installed or removed at some point ) . It should be noted the water spraying out of your junction elbows can also wreak havoc with the 951 as it’s sucked in to the motor… But back to your current issue . Water in the air box means your motor did inject some water . On the 951 , gulping water usually doesn’t hydro lock the motor , it merely washes the cylinders ( cold water takes the place of the hot gas oil mixture between the piston and cylinder wall ) which chews the piston up and creates friction and puts deep grooves in the cylinder.

Motor will run but will exhibit the exact symptoms you describe .

Recheck your compression and let us know what it is now.
Good Luck -
WMaker

Thanks for the detailed post widowmaker.

To clarify, my ignition coils being out of spec does not cause you concern?

I have not checked the carb pop off pressure.

Thankfully I am fairly certain the engine is still good. It has been doing this odd behavior since day 1 of having the ski, and when I bought it last May, compression was strong. I will check compression again next time I'm at the ski, but these were the results I obtained last July with a quality, USA-made compression gauge. This is after the lions share of the water in the hull had already occurred and I knew I had a problem, and the ski has only been ridden in conservative testing fashion since then. I had also since learned the correct orientation of the rubber airbox flaps to help keep water out.

Perfect compression on the 947 is 130 PSI, correct? If so, these results being tested at 1600 ft elevation are totally serviceable. It's also worth noting, as I've described in prior posts, the ski screams for the first 30 seconds. It hits 58 or 59 MPH (tested with a GPS speedo) in this timeframe, which I don't believe a low compression ski would be capable of. Then, after that first little bit, it shits itself back into the vicious cycle.

As an aside, my buddy has a 2001 GTI. Last summer, it took on a LOT of water from a broken through-hull fitting, there were 10+ gallons of water inside and the MPEM was completely submerged for about 30 mins. It's a relatively low-hour ski in fantastic shape and his family is the original owner, but it has now started doing the exact same thing my XPL does. It actually runs fine for 4-5 mins, but after that it bogs down and accelerates just like in my video above. These folks are still running the grey tempo lines and original carb kit, which I explained are problematic and need to be replaced.

So, if your theory is correct, perhaps we both are in need of carb rebuilds with Mikuni kits

 

[Widowmaker2011]

The symptoms you describe do not correlate with electrical/coil . A Coil that breaks down electronically will start to spit and have misfires and based upon the way you are describing your symptoms, it doesn’t sound like that at all.

The reason I asked you to check your compression again was to compare it to the original readings that you had. Your original readings at 6000 feet. Elevation were fine. I agree. I’m just going to ask you to trust me that if there was actually water even a tiny bit sitting in your airbox, some of it was ingested and it can have a considerable impact. The very first technical service bulletin on the 951 engine was to add flaps to keep water from splashing into the airbox, because even a couple tablespoons of water sucked in during high acceleration can mean the damages done.. I have seen the Rotax 787 and 720 cc Sea-Doo motors survive multiple water ingestions, however the 951 is a different animal and very susceptible to damage of the cylinder walls and pistons with even minimal water ingestion.

Aside from that , absolutely check the pop off pressure. You can buy a good pop off pressure gauge for about $50-$75 or you can borrow one and it cannot be understated how much better an actual mikuni rebuild kit is vs any of the aftermarket manufacturers. I’m not against aftermarket parts. I run several parts that are not OEM on my boats but in this case it’s pretty critical.

Lastly , your description tells me that fuel is getting into the carburetors, but you’re not able to flow enough to keep up with the demand once it gets up to high-speed. The motor will draw in a lot of fuel during acceleration and then it will reach top speed, running fine, but it has scavenged all of the fuel at Ken out of the carburetors, and the fuel system is not replenishing it fast enough , thus the drop in rpm. These boats were actually jetted a tiny bit rich from the factory so using stock Jets and settings should give you more than enough fuel, unless you have heavily modified the boat.
It’s always important to eliminate possibilities before getting into the weeds and what it possibly could be in the very first thing you do in any situation even if it’s not a Sea-Doo is to ensure that you have factory parts in the critical positions. Good luck let us know how it’s going.

 

[SeaDooDoo90]

I had the same problem with a 2000 gtx, same engine. Didn't work unit full genuine mikini carb kits were installed.

I had the same problem with a 2000 gtx, same engine. Didn't work unit full genuine mikini carb kits were installed.

I believe you are the 2nd or possibly 3rd poster in this thread to report the same issue which was eventually solved with genuine Mikuni rebuilds.

My cognitive bias didn't want to accept this, as I would rather crawl naked through a mile of glass shards than remove/install that carb assembly again. But, it is time to face the facts!

 

[SeaDooDoo90]

The symptoms you describe do not correlate with electrical/coil . A Coil that breaks down electronically will start to spit and have misfires and based upon the way you are describing your symptoms, it doesn’t sound like that at all.

The reason I asked you to check your compression again was to compare it to the original readings that you had. Your original readings at 6000 feet. Elevation were fine. I agree. I’m just going to ask you to trust me that if there was actually water even a tiny bit sitting in your airbox, some of it was ingested and it can have a considerable impact. The very first technical service bulletin on the 951 engine was to add flaps to keep water from splashing into the airbox, because even a couple tablespoons of water sucked in during high acceleration can mean the damages done.. I have seen the Rotax 787 and 720 cc Sea-Doo motors survive multiple water ingestions, however the 951 is a different animal and very susceptible to damage of the cylinder walls and pistons with even minimal water ingestion.

Aside from that , absolutely check the pop off pressure. You can buy a good pop off pressure gauge for about $50-$75 or you can borrow one and it cannot be understated how much better an actual mikuni rebuild kit is vs any of the aftermarket manufacturers. I’m not against aftermarket parts. I run several parts that are not OEM on my boats but in this case it’s pretty critical.

Lastly , your description tells me that fuel is getting into the carburetors, but you’re not able to flow enough to keep up with the demand once it gets up to high-speed. The motor will draw in a lot of fuel during acceleration and then it will reach top speed, running fine, but it has scavenged all of the fuel at Ken out of the carburetors, and the fuel system is not replenishing it fast enough , thus the drop in rpm. These boats were actually jetted a tiny bit rich from the factory so using stock Jets and settings should give you more than enough fuel, unless you have heavily modified the boat.
It’s always important to eliminate possibilities before getting into the weeds and what it possibly could be in the very first thing you do in any situation even if it’s not a Sea-Doo is to ensure that you have factory parts in the critical positions. Good luck let us know how it’s going.

Those compression figures above were not the original readings at 5000 ft elevation, they were taken at 1600 ft. IIRC both cylinders were hardly pushing 100 PSI at 5k ft, but I don't think that's a surprise given the correction factor. I will be sure to check again just to make sure, but I'm 95% certain I will get the same readings. I don't doubt my engine has sustained at least some water ingestion, but in this case I either lucked out, or it was too trivial even for the 947 thanks to the airbox flaps.

I have the pop off pressure tester from OSD Marine, though didn't buy that until after I installed the Venom kits.

I will get a new set of Mikuni rebuild kits on order and test pop-off prior to reinstallation.

 

[Widowmaker2011]

I am in the process of replacing fuel lines on both of my XP limiteds and putting new Mikuni kits in the carburetors . The best way I can describe taking the carburetors off that motor in the XP hull is that I learn a new swear word I didn’t know existed every time I do it.

 

[SeaDooDoo90]

so true. It's one of the most challenging mechanicals procedures I've ever attempted, certainly the most so on a watercraft.

When I initially had them back together after installing the Venom kits, I somehow managed to hang up the throttle cable and it redlined upon start up. I'm just glad it didn't completely run away on me like I've had a Kawi do out of the water and the DESS key immediately killed it.

 

[SeaDooDoo90]

Finally got around to testing compression again, and this time I held WOT. Looking better than ever, holding the throttle open added about 15 lbs per cylinder.

I'm going to pull the carbs and rebuild with all Mikuni now.

 

[SeaDooDoo90]

Carbs are out and I've rebuilt them with OSD's 'back to OEM' kit. Also replaced the fuel line in the accelerator pump.

What should I run the adjustment screws at? I know factory spec is 1-1/2 turns on the low speeds and 0 on high speed, but I recall reading somewhere on this forum something about 1/4 turn open on one of the high-speeds

 

[SeaDooDoo90]

Got the carbs back in today. Water tested and it's ripping. Problem finally solved - thank you for the help everyone.

I think it's running a bit fat down low. It has a slight hesitation/bog when cracking the throttle from an idle. Honestly, it's nothing I can't live with, once it's off idle the throttle response is instant and it screams at all RPM levels.

I checked the plugs after a sustained WOT pull, and they look perfect, so I'm hesitant to mess with anything, but should I consider turning the low speeds 1/8 turn closed?

I'm currently at the factory spec of low speeds 1-1/2 turns, high speeds 0 turns.

 

[FL-Rider]

Glad to hear you got it running good. Thanks for following up. On the adjusters, you'll just have to make tiny adjustments like you mentioned and do trial and error.