• This site contains eBay affiliate links for which Sea-Doo Forum may be compensated.

RFI Injector Mystery - Or Something

Status
Not open for further replies.

kleary

New Member
Greetings - My 99 GTX-RFI is dead in the water. I don't know why, but I have lots of observations, so bear with me. Any and all help would be greatly appreciated. Here's the rundown:

-Ski has run great all year. After a long day on the water, my son paddled it in.
-No evidence that anything was amiss, except that when he chopped the throttle 100 yards offshore, it stalled rather then returning to idle.
-Found the oil tank completely drained and the oil lines to the rotary valve dry (teenagers, grrr!). Very bad, but it doesn't seem terminal. I refilled the oil tank and primed the lines. Plenty of oil in the bevel gear chamber and do I run a little oil in the gas (a habit from the break-in period from a top-end job four years ago).
- Engine spins fine. Seems to fire once, then stops immediately. Some evidence of backfiring through the intake. Very repeatable.
- Spark on both cylinders
- Seems to be good compression on both cylinders, although I didn't measure.
- No metal particles to be seen anywhere.
- Exhaust seems all clear. Disconnected exhaust down by the muffler. Seems all clear.
- Crank position sensor looked clean and connected. No contamination in magneto housing.
- Spinning the engine without plugs, I noticed that front cylinder was blowing fuel mix, but the rear was not.
- Replaced only the front spark plug, and the engine starts and runs, but very rough.
- Pulled the fuel rail and removed both injectors. Both look clean and undamaged.
- Spun the engine, and both injectors spit seemingly equal plumes of fuel
- Replaced fuel rail. Spun the engine, and getting only fuel to the front cylinder!!!!!
- I'm getting the Low 12V display, but it may have only showed up after lots of cranking. Not sure. No other warnings.
- New battery this year. No previous evidence of charging problems.
- I believe the 12V low error does stay on even when I jump the battery from another boat.
- I've heard about limp home mode, but I've never experienced it. Could the rear injector be spitting during startup then cutting out right away? I spun the engine for a few seconds with the fuel rail removed . . . enough to put a good coating of fuel on the ski! I didn't notice any evidence of the rear injector turning off.

So . . . When I saw the oil starvation, I was ready to call it a year and start shopping for a crank. Then I thought I had dodged a bullet, and was being hit by an entirely unrelated fuel issue. But I'm not a big believer in in coincidence, so I'm thinking this is a secondary symptom of a minor seize in the crank or Rotary Valve.

Sorry for writing a book on this one . . . but I could really use some ideas! Thank you in advance.

Kevin
 
I didn't read the whole post but already saw the first part about running oil in the gas. I believe this is a no no on an Rfi ski
 
sounds like a stuck rotary valve

Does the Bevel Shaft disengage from the Crankshaft somehow? Because the Rotary valve is hardened steel set on a beefy spline with no obvious way to disengage from the Bevel Shaft. If the Disk started seizing, i'd expect a loss of power before shutdown and evidence of aluminum shavings in the engine Neither of these a present. Also, I'm getting plenty of airflow from both open sparkplug holes. So its working well as an air pump . . . just missing the internal combusting!
 
If the rotary valve is stuck the piston will still move up and down and push air out of the spark plug hole but will not let any of the fuel/air mixture from the intake in. The gear on the crank is steel and so is the gear that the rotary disc is on but the gear on the rotary shaft that engages the crank gear is brass and is designed to strip out before the crank is damaged. Running with no oil could cause the shaft to stop and strip the brass gear. Only way to tell is to pull enough of the intake to see if the rotary valve is moving.
 
it does idle on 1 cylinder, running out of oil , did its damage for sure, and backfiring is usually rotary valve and/or compression ..even if you have oil in the gas on a rfi, the gas is shot in on other side of motor, and it would only lube the top of piston ... oil and air comes in through the t/body and lubes it all .. you hurt it, by running it out of oil ... it siezed, and when it cooled down it started.
 
it does idle on 1 cylinder, running out of oil , did its damage for sure, and backfiring is usually rotary valve and/or compression ..even if you have oil in the gas on a rfi, the gas is shot in on other side of motor, and it would only lube the top of piston ... oil and air comes in through the t/body and lubes it all .. you hurt it, by running it out of oil ... it siezed, and when it cooled down it started.

Yep - Understood about the oil paths. What I don't understand is how it can run on the front cylinder without the Rotary Valve turning. Or how it could seize enough to strip the brass gear without a single aluminum shaving migrating into the cylinders. But I agree with you and Miki that the next step is to pop off the intake. That'll have to wait for the weekend unfortunately . . . when I'd rather be OUT on the water! I'll let you know what I find.
 
I think you need to check the compression using a known good gauge. Idling on 1 cylinder, this one does (apparently), thus that injector shuts off (I would imagine).

A NOID light plugged into the injector harness connector will tell you if the MPEM is firing the injector.
 
I took things apart and indeed it was a Rotary Valve scrub due to lack of lube. The Brass gear looked like a corn cob with all the kernels eaten off. So two more questions before I reassemble:

1) What is the best way to flush the metal shavings out of the oil bath? The tube fittings look like they're pretty low in the casting, but not at the bottom. I have a vacuum oil changer, so can more oil/debris be sucked out somehow?

2.) it looks like there is about 0.06" of end play in the Gear/Spring/Spacer stack. Is this normal, or is the spring sacked out and in need of replacing? Thanks, Kevin
 
Status
Not open for further replies.
Back
Top