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  1. #1

    FX HO injectors dumping fuel

    Help! Just bought a pair of 05 fx ho's. They both have 200 hours. One runs perfect, the other is dumping fuel past the injectors. I know this because I attempted to do a compression test prior to buying it and one cylinder blew so much fuel into the cylinder, I couldn't test it. The other three tested to 180 and this one appears to have plenty. I figured that the one injector was stuck/clogged so I replaced it. Now, after putting it all together, all four cylinders are blowing fuel out the plug holes. Given that the injectors are controlled electronically, what would cause them to stay open long enough to pump large quantities of fuel. Liquid fuel sprays out of the cylinders when I turn it over with the plugs out. The good news is I have a lot of "known" good parts to swap to figure it out any suggestions? Needless to say the oil has a lot of fuel in it.

    Any ideas would be appreciated.


  2. #2
    SHOBiz's Avatar
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    Pull the injectors from the ski that is okay and try them in the other ski.

  3. #3
    SHOBiz, thanks for the response. I did replace the offending injector with a new one and same issue. Took your advice and switched the entire throttle body and fuel rail from the good one and still have the issue. I think I am getting somewhere, at least it is not in those parts.

    Anyone know if the fuel pump unit has some sort of regulator? I suspect I am dealing with pressure too high and that is what is causing the excess fuel. (seems like excess pressure or duration is the only thing that would allow so much fuel to get to the cyl). I have the factory manual but the descriptions are cryptic and they don't really show the pump assembly in much detail. I don't have a fuel pressure guage but I think I will buy one. Switching the fuel pumps looks like a job. Anyone replaced one recently? I notice that there are check valves and such but I don't see a return line from the throttle body like a car would have. Is that a return line somewhere in the pump assembly?

    I noticed that the bolts on the offending ski's throttle body have been hosed up a bit so who knows what has been done to the ski. Good news is that I got a good enough deal on the pair that one can be a parts ski if it comes down to it. Again, any further ideas would be a great help.

  4. #4
    SHOBiz's Avatar
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    Hmmm. So am I reading this correct that this is a single injector? If so, if it is not the injector I would be looking at the wiring to that injector and then the ECU. The fuel regulator or fuel system SHOULD affect all injectors if that was involved at all. Odd if no wiring or ECU issue is found.

  5. #5
    Thanks for the response. I will trace the wiring back. Does the injector wiring go back to the ECU? Now that you mention it, voltage from either the other injectors or any source could fire that injector and cause the issue. Are there issues with moisture in connections or do you think I should concentrate on chafing?

  6. #6
    nicjak's Avatar
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    you are holding the throttle wide open when you are testing compression arent you? this on most ecu ski's switches the injectors off.

  7. #7
    SHOBiz's Avatar
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    Quote Originally Posted by nicjak View Post
    you are holding the throttle wide open when you are testing compression arent you? this on most ecu ski's switches the injectors off.

    ???
    It's ONE injector doing this ALL of the time...

  8. #8
    Making progress... Finally took the injector harness loose and tested each wire for continuity. The "offending" injector wiring was "open" for a while until I untaped the harness and moved the wires around a bit. Now, having the positive side be "open" would seem like the injector wouldn't fire at all, but my thoughts are that if there is a break or a weak spot in the wire, it might be picking up pulses from one of the others or maybe even a constant feed from something else causing it to be open. No noticable rub throughs on the insulation. Bottom line is the harness is probably junk at this point. I have a line on a used one. (Yamaha wants 250.00). I will now take the harness off the good ski...(no fun but I can be certain that my ECU is good) and test.

    No, I did not have the throttle wide open to do the compression test but I did unhook the injectors and got 240psi on all four cylinders. Now I know at least I don't have a very large pile of parts on my trailer. I put a new set of plugs in the machine, unhooked number two injector and it fired right up. Runs amazingly well on three cylinders throttle response is quicker that the VX... Thanks to SHOBiz for the insight and suggestions. Thanks to NicJak for reminding me of the correct way to do a compression test.

    Now for one more question. If you had a crankcase (oil sump) full of fuel diluted oil, how would you get it all out? I use a "sucker" machine to do oil changes but I barely get two quarts out when I use the tool. Before I water test this ski, I would really like to get the oil completely out and some fresh oil in. Anything other than doing a couple of oil changes back to back to hopefully exchange enough of the bad oil to get back to good?

    Oh yeah, anybody got a couple of "serviceable" trim cables and a reverse cable they would like to sell? This poor ski has had a rough life and all three are rusted so badly internally that when I lubed them then attemped to pull on them, the outer sheathing collapsed. I would buy new ones if I intended to keep the ski but I bought the pair of skis to keep the better one of the two so the goal is make it work "properly" and let someone else go broke making it new again.

    Gentlemen, thanks again for the help. I can only imagine what it would have cost to pay someone to track down a faulty wiring harness. This forum rocks!

  9. #9

    Wiring harness problem found!

    Well, thanks again to SHOBiz for suggesting a wiring problem. I took the harness out of the ski, tested all the pins and found what I thought was a continuity problem but that must have been me just not making good contact. I re taped it all up and put it back in with the same injector seeming almost always on and pumping fuel into #2 cyl. I ordered a used harness from a guy off ebay and I am waiting for it but I wanted to get to the bottom of the issue so off again and I began testing for voltage drop on all the circuits. (should have done that first). Well, when I ran 12volts to each pin in the main plug (one at a time), I got .2 to .4 volts coming out of every other wire. (except the one that had 12volts hooked to it). Now where in the hell would I pick up that much voltage in a harness that showed no damage or crimped wires of any kind? I inspected every inch, sprayed brake clean in all the plugs and dryed them, and still got the trace voltage. I looked at the big rubber grommet that goes in the bottom of the airbox. I pulled on the wires to move them and they barely budged. I then tried to slide one wire at a time and they pretty much moved freely. The first one I moved was the positive lead to the offending injector. After moving it, some of the trace voltage went away. I then moved all the wires about an inch out of the grommet and all trace voltage went away. The area of each wire that used to be in the grommet has some strange looking crimping on the insulation. I tested this area with 12 volts running through and sure enough, trace voltage. I am guessing that vibration weakend the isulation and moisture in the rubber grommet did the rest. Apparently when the other injectors fired, enough voltage leaked to number two injector to fire also. Strange but true. I taped each individual wire up around the crimped area and put the harness back on the ski. Fired up immediatley and runs perfect. Cannot wait to get it out on the water. I hope others can learn from this. I would bet there is a technical service bulletin out for this but I do not have access to Yamaha TSB's. Does anyone on the forum have access? I would love to know if there are any other "issues" with 05 HO's.

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