Lost 250-300 RPM on 2003 XP DI

[Team Bilford]

Pull the Raves and look for scarring on the exhaust side of that front cylinder. Low fuel pressure on the DI tends to eat up the front piston first.

I looked at the cylinders when I had the RAVEs out earlier and saw no issues. Remember that the problem is frequent, but intermittent. If it was compression or reed, the problem would be constant, it is not.

I haven't looked at the water control valve on the water box. Doesn't the valve restrict water flow on the top end? If it was clogged, wouldn't the top end run cleanly and show a loss of power on the bottom? I don't see any signs of excessive heat on any of the exhaust couplings.

[Myself]

If everything else looks good, AND there's no corrosion or rust in the coil box,....then it might be time for a simple fuel filter change. You can hook up a gauge inline and go for a ride and watch what happens with fuel pressure at wot.

[nmpeter]

I would be suspect of the air injectors, 200 hours seems to be the typical lifespan of those bits, sad to say they have been discontinued and serviceable ones are as rare as a vegas virgin during EDC week.

Checking the fuel pressure while wfo is also, as previously mentioned, suggested.

I would give the water box control a real good look especially where the clip sometimes will poke a tiny hole in the diaphragm

The Di was a great ski in its day, but like my beloved 1986 3g honda accords, they eventually reach the end of their track with the lack of absolutely vital parts being discontinued and the supply of salvage parts being exhausted

while 300rpm off the top isn't exactly the end of the line, I see red lights in the distance, so enjoy her while you can.

In the world of computer controlled combustion 17 years is damm good

Partszilla surprisingly still have a few in stock(maybe) 275500545 good price too compared to what people are profiteering on ebay.( double the price!)

Since these bits are discontinued, if you are committed to keeping that di as long as you can bite the bullet, drop a couple of hundred on a pair, install the new ones and go from there. With new air injector in place you have a better chance of getting to the bottom of the rpm loss and reduce the chance of a engine failure if and when one of them finally do crap out.

again, as mentioned, air injector faults do not throw codes, so while its a guess, I can tell you that every injector I ever replaced ( and there were quite a few, as I was one of the very few shops that would take them on) all had over 200 hours on them

Just for reference, when I moved to New Mexico I took some of my NIB accord parts with me, including a brand new carb. I sold that on ebay and in the end I was absolutely flattened to the last minute bidding war

The accord carb was literally the most complicated thing on earth and the new one was as rare as an albino elephant. It sold for over $1000. I recall paying $350 for it..didn't need it as I eventually found the pinhole leak in a vac line that was causing me to fail an emissions test in NJ ( they used a dyno there).

good luck

[Team Bilford]

If the air injector does not throw a code, is there a way to test it without plugging in new parts? The ski starts and idles perfectly, would the air injector only cause issues up top? I have never had the fuel sending unit out of this ski and have never changed the fuel filter. Since the problem shows at higher fuel demands, maybe the filter should be R&R as a possible issue. The problem did not come on slowly, it was instant all at once after filling with fuel. That's why I was only suspecting bad fuel.

[nmpeter]

there is an electrical spec for the air injector's resistance, but that won't tell the entire story, neither will checking the air pressure coming out of the pump

Obviously you'll want to check the actual fuel pressure at wfo and perhaps change out the filter too. careful on the filter, the fuel pressure on DI is quite high so you must use the correct spec filter for it

an air injector malfunction can go either way and you can seize the engine from an overly lean condition if the injector cannot keep up with the expected pulse rate. In the orbital system the air injector is used to atomize the fuel so less the adequate pressure will mean an uneven fuel burn at high rpms, like a leaky valve on a 4 stroke, not very noticeable at the top end except for the loss of rpms

I'm assuming you have a candoo and have also zeroed the TPS.

I bought a poorly winterized DI the first month I opened my shop for a song and used those parts to confirm my diagnostics on that particulkar model, as I quickly found the candoo cannot provide any data on the air injection system unless the injector failed totally and threw the MAINT lamp

Of course labor is free compared to parts, so certainly pulling the sender to check the tank sock and fuel condition is a cheaper solution then spending hundred on parts. I'd concentrate on the fuel pressure, far easier to check then the tank sock

Of course if you don't have a spare injector on hand when one goes out, the ski is sidelined. I think its a good investment/insurnace to perhaps just buy one, there will always be a market for them and you can easily get your money back at end of life.

I sold both of my test injectors for the new price ( that DI actually had ten hours on the meter when it came in with water in the engine) when I shuttered the two stroke side of my business as the customer that needed them was always good to me and at the time, they were pure unobtainum, at any price.

I still have the fuel injectors and the rail. I sold the exhaust manifold a few years ago and I still haven't pulled the rusted engine out. I know good cases for the DI are like gold, so I'll eventually get around to that, or not. I've gotten a little too old(still younger the steve45 to be dicking around with stuff I'm not making really good money on, not that I've been open at all this year due to covid and our draconian governors policies on shutting our lake down without much notice, and then only allowing in staters to use it, with no overnight camping.

If you have a sales tax certificate and a physical business you can get those parts at dealer cost from partzilla and if things work out on the fuel side, you can just list them on ebay for retail, they _will _ sell.

so end advice, leave the air injector to the hail mary and go thru all other possibilities first. I don't like dropping a couple of hundred on a guess either.

My very expensive kitchen aide 5 door refrigerator developed a fault in one of the controller boards and the replacements were hundreds of bucks. Rebooting the fridge solves the problem. Lately it has not misbehaved quite so much so I count myself lucky I didn't drop $500 on the power supply or controller board only to find out it was the "other one"(the boards are exchange only). I didn't get an extended warranty for this one as nobody in elpaso knew how to fix my samsung when the compressor failed and after being without a fridge for 5 months ( and having paid $500 a year for the contract-which came in handy the couple of times the icemaker crapped out) I threatened to sue sears and they coughed up the kitchen aid for a small extra payment (american made), but the compressor still came from chy/na. So I know the pain of dealing with a black box problem

[Team Bilford]

Thanks to all of you that have taken the time to post. My season has ended and I won't be able to test ride till next year.
What is the best gauge to use on the fuel rail? Is it a standard Schrader connection?
I don't have a fuel pressure rig, so I'll have to buy one.

[Myself]

You can rent a fuel pressure kit from the auto parts store. There is no test port. You must insert an adapter tee in the supply quick connect fitting. I believe it's a Ford type.

[winterstick]

Check the fuel filters in the tank

[Team Bilford]

Check the fuel filters in the tank

I agree that the in tank filters could cause high demand fuel flow issues. The problem started immediately and not over a period of time making me lean towards electronic or mechanical, not filter.

Can the filters be cleaned and reused or should they be replaced? If they need to be replaced, then I would have to find them before starting that task.

[nibroc]

replace the filters