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  • Plugs keep fouling - any thoughts??

    I have a 2002 X-30 with the 8.1L engine with almost 800 hours. Over the past year, I have replaced the plugs 3 times. Each time its because most (not all - only 5 of 8) plugs are fouled. The boat runs fine, doesn't miss fire or sputter (technical term). I have had fuel issues over the past year and have done the following in maintenance and repairs.

    1) Replaced fuel pump with a new Millennium fuel pump
    2) Replace the MAP sensor
    3) Replaced the fuel pump relay
    4) Replaced the fuel rail fuel regulator (had no idea that was even there)
    5) Replaced the spark plug wire set
    6) Checked using a spark plug tester that all coil packs are operational
    7) Check the compression of each cylinder. All measured around 155 - 160 psi.

    I have no idea what is causing the spark plugs to foul in less than 10 hours of operation.

    At least this is not stopping us from using the boat but I would like to figure it out. I am chewing through fuel even more than more with this engine.

    Any and all thoughts are welcome...
    2002, X30, L-18, Red Metal Flake (the possessed boat)

  • #2
    Whats your fuel pressure while running?

    Have you tried an injector cleaner? I am a big fan of Star Tron Ring Clean.

    Have you tested or disassembled and cleaned the injectors?

    Comment


    • #3
      I'm assuming they are fouling from being rich and not from oil based on your comments. It has to be something fuel related and not spark. Is the exhaust also black and sooty? On a car or truck I would expect the exhaust tips to also be black, but on a boat the water probably washes this away. You want to be sure this is a fuel problem and not an oil burn problem.

      As the other person suggested, check your fuel pressure while running and maybe try replacing a couple of injectors, or swap injectors between a good/bad cylinders and see if the fouling problem follows the injector.

      Comment


      • #4
        Originally posted by lakedrum03 View Post
        Whats your fuel pressure while running?

        Have you tried an injector cleaner? I am a big fan of Star Tron Ring Clean.

        Have you tested or disassembled and cleaned the injectors?
        I suspect it is a fuel issue because it does have a smell of fuel (more than normal) when running. When I replaced the fuel pump, my pressure when running was 48 psi which is low compared to what Indmar says it should be. I haven't taken fuel pressure readings since I replaced the fuel rail regulator.

        I have dumped in some fuel injector cleaner in my last tank but I have not removed or cleaned any of the injectors. They are 20 years old.
        2002, X30, L-18, Red Metal Flake (the possessed boat)

        Comment


        • #5
          Originally posted by robadele View Post
          I'm assuming they are fouling from being rich and not from oil based on your comments. It has to be something fuel related and not spark. Is the exhaust also black and sooty? On a car or truck I would expect the exhaust tips to also be black, but on a boat the water probably washes this away. You want to be sure this is a fuel problem and not an oil burn problem.

          As the other person suggested, check your fuel pressure while running and maybe try replacing a couple of injectors, or swap injectors between a good/bad cylinders and see if the fouling problem follows the injector.
          Yes, I believe the engine is running way too rich. I burned a quarter tank of gas (15 gallons) in about 1.5 hours of clock time. Yes, the 8.1L is thirsty but that is not normal and I've owned this boat for 18 years.

          What is weird is since I've replaced the plugs 3 times in a year and have kept and labeled each plug with the cylinder number, the fouled plugs seem to be random in cylinder location. This time its cylinders 2 - 6 with 1, 7 & 8 looking great. Going back to those same cylinder's plugs the other times they were changed and it is different ones that are fouled. Makes no sense.

          Looks like I'll be removing the injectors and cleaning then this winter or replacing them if needed.

          Any other ideas?
          2002, X30, L-18, Red Metal Flake (the possessed boat)

          Comment


          • #6
            Originally posted by lakedrum03 View Post
            Whats your fuel pressure while running?

            Have you tried an injector cleaner? I am a big fan of Star Tron Ring Clean.

            Have you tested or disassembled and cleaned the injectors?
            If the injectors where dirty, wouldn't that cause the engine to run lean, not rich?
            2002, X30, L-18, Red Metal Flake (the possessed boat)

            Comment


            • #7
              A leaking injector will allow to much fuel as it won't shut off for the correct number of pulses. It may be possible to have an injector that is stuck open slightly. Cleaning the injectors is not as good as replacing them, but is super easy/cheap and has a small chance of working.

              Otherwise you are correct, a clogged injector would not deliver enough fuel and you would probably have issues under full throttle. Do you have full throttle issues like missing/bucking?

              One other thing to check, does your oil smell like fuel? With a leaking injector, not all the fuel burns and the oil gets polluted with fuel.

              Comment


              • #8
                Originally posted by robadele View Post
                A leaking injector will allow to much fuel as it won't shut off for the correct number of pulses. It may be possible to have an injector that is stuck open slightly. Cleaning the injectors is not as good as replacing them, but is super easy/cheap and has a small chance of working.

                Otherwise you are correct, a clogged injector would not deliver enough fuel and you would probably have issues under full throttle. Do you have full throttle issues like missing/bucking?

                One other thing to check, does your oil smell like fuel? With a leaking injector, not all the fuel burns and the oil gets polluted with fuel.
                After replacing the fuel rail regulator, I was able to regain my top speed of 43 mph. I will check to see if the oil has fuel odor. It does burn more fuel than it should even for a 8.1L big block.

                Where is a good place to get new injectors, if that is what I need?
                2002, X30, L-18, Red Metal Flake (the possessed boat)

                Comment


                • #9
                  Is your 2002 8.1L an Indmar engine? I think it is and Indmar used GM fuel injectors. The question is which GM part number.

                  You may need to search the board and/or contact Indmar.

                  I think this is the correct one, but you should verify

                  https://fuelinjectorconnection.com/p...lphi-e10-ready
                  Last edited by robadele; 09-08-2021, 05:04 PM.

                  Comment


                  • #10
                    you can pull your injectors and send them off for testing/cleaning/flow balancing without having to replace them. id probably lean that way if you have some down time this fall/winter
                    and doing that may actually net you better results than buying some random new injectors online.


                    Originally posted by prostar205 View Post
                    Each time its because most (not all - only 5 of 8) plugs are fouled. The boat runs fine, doesn't miss fire or sputter (technical term).

                    At least this is not stopping us from using the boat but I would like to figure it out.
                    but, this makes me have to ask - how are you determining that theyre so fouled they need replacement if its not causing running issues?
                    just that theyre black? that they smell funny? that theyre not all the same color? is it always the same handful that are "iffy"?
                    you could try moving injectors during a plug change to see if the iffy plugs follow an injector - but again if youre going that far id just send the injectors out for service.

                    i know it takes a few minutes - but maybe next time you pull them for replacement, take pictures of all 8 and post them here.

                    Comment


                    • #11
                      Personally I wouldn't jump on the injectors until I'd checked a few other things.

                      If it's just running rich (sooty or mildly wet plugs) then it could be more likely from the following things:
                      1) Poor Earth (sensor-block/loom-block)
                      2) Poor/loose connection somewhere
                      3) Miss reading / failing ECT
                      4) vacuum leak somewhere
                      5) Miss reading / failing O2 sensor

                      Non of them would throw an engine code as the sensors would still read within normal range, just slightly higher or lower than actual, tending to a rich mix.

                      You've done a lot of work on the engine so it may be worth just running through and checking each sensor plug is OK, no loom rubbing has occurred, earths are good and the plug wires are correct order (done that!)

                      Finally, take it for a blat and clear the system out, nothing worse than just sitting at a 2000rpm for 3hrs chugging away if a sensor is reading slightly out

                      Comment


                      • #12
                        Originally posted by chrislandy View Post
                        Personally I wouldn't jump on the injectors until I'd checked a few other things.
                        it being port injected and the plugs showing some degree of variability (tough to say without pics...) is what led me there

                        Comment


                        • #13
                          Originally posted by robadele View Post
                          Is your 2002 8.1L an Indmar engine? I think it is and Indmar used GM fuel injectors. The question is which GM part number.

                          You may need to search the board and/or contact Indmar.

                          I think this is the correct one, but you should verify

                          https://fuelinjectorconnection.com/p...lphi-e10-ready
                          Yes, the engine is an Indmar engine.

                          I got the GM part number from Indmar customer service. It's PN 12575073 (Indmar PN 551337).
                          2002, X30, L-18, Red Metal Flake (the possessed boat)

                          Comment


                          • #14
                            As a note, many of the Indmar engines of that era are open loop control, no O2 sensors. My 99 5.7 LTR is this way and I think the 8.1L is the same way. Not sure about the 6.0.

                            Comment


                            • #15
                              Originally posted by ValveCoverGasket View Post
                              you can pull your injectors and send them off for testing/cleaning/flow balancing without having to replace them. id probably lean that way if you have some down time this fall/winter
                              and doing that may actually net you better results than buying some random new injectors online.




                              but, this makes me have to ask - how are you determining that theyre so fouled they need replacement if its not causing running issues?
                              just that theyre black? that they smell funny? that theyre not all the same color? is it always the same handful that are "iffy"?
                              you could try moving injectors during a plug change to see if the iffy plugs follow an injector - but again if youre going that far id just send the injectors out for service.

                              i know it takes a few minutes - but maybe next time you pull them for replacement, take pictures of all 8 and post them here.
                              I have had fuel issues since last Aug. 2020. I replace the fuel pump but had low fuel pressure (48 psi). I could not get the boat past 3,000 rpm/30 mph. While trying to fix that issue, I pulled the plugs only to find most (not all) completely black some with crystals around the base of the electrode. There is also a stronger than normal smell of fuel when running. Here are some pictures of a couple of plugs that I am referring as being "fouled" and this is only after 5-7 hours of engine run time.
                              Attached Files
                              2002, X30, L-18, Red Metal Flake (the possessed boat)

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