Announcement

Collapse
No announcement yet.

Strong misfire when starting?-gctid418144

Collapse
X
  • Filter
  • Time
  • Show
Clear All
new posts

    Strong misfire when starting?-gctid418144

    I wonder if anyone has an easy answer before I spend a fortune. . .

    I had a few issues with a misfire when running so I changed the coil, plugs, distributor cap and rotor and checked all the relevant wires. I also changed the fuel filters and checked the gauze filter on the mercarb2. The fuel side looked good. The plugs looked rusty but were a good slightly sooty brown. No water present. The exhaust is new.

    The engine is a 5.0L carbed v8 in a 1998 2452.

    After all that work, I now have a fuel efficient and sweet running engine again. The trouble is that it can do a huge misfire when starting. It is so bad that it stops the engine spinning and the nav computer turns off. It doesn't do it everytime. It is about once every 5 starts. Maybe it is when I pump the throttle to prime the carb. It has not done this before the misfire was noticed.

    I am still waiting for a timing tape to turn up but as soon as it arrives I'll check the timing and look for jitter. However, when the engine is started it runs really well. I am getting 1.8 to 1.9 litres/Nm at 22 Knots which is good as it gets on a 2452 in choppy British seas. I couldn't image the timing being out (but I am open to all suggestions).

    Anyone have any ideas?

    Terry
    Terry (Retired Diving Instructor and Part Time IT Consultant)
    1998 Bayliner 2452. 5.7l V8 - Edelbrock 1409 4bbl - Alpha1Gen2 - Solent UK.
    MMSI 235061726

    #2
    My guess is timing but until you can test it you wont know.

    Other choices are bad plugs/wires just because they are new doesnt mean they are good. Worn timing chain worn distributor bad valves.

    A compression test might be good and its cheap to do your self. That will rule out the valves.
    1989 Avanti 3450 Sunbridge
    twin 454's
    MV Mar-Y-Sol
    1979 Bayliner Conquest 3150 hardtop ocean express.
    Twin chevy 350's inboard
    Ben- Jamin
    spokane Washington

    Comment


      #3
      Rusty plugs raised my uh oh alarm.

      Where was the rust, on the outside or on the part in the engine?

      Doug
      Started boating 1955
      Number of boats owned 32
      Bayliners
      2655
      2755
      2850
      3870 presently owned
      Favorite boat. Toss up. 46' Chris Craft, 3870 Bayliner

      Comment


        #4
        Have you had the carb off lately? The q-jet has a few inherent flaws. One of them being the fuel wells. These wells are where the jets for the primaries pick up fuel off the bottom of the fuel bowl. These wells have a bad tendency to leak as the carb ages. They are leaking so badly on my OMC that it has a very rough idle and the carb will need this repaired in the spring.

        One way to tell it they are leaking is just by starting it. If you let the boat set for a few days, does it pop right off when you try to start it? If it has to be cranked for a few times then the fuel bowl is most likely dry from leaking down.

        If this ends up being the problem, the way to fix this is to obtain a rebuild kit for the carb, pull the well plugs, press in the new ones from the kit, and then thourally clean the outside of the wells with carb cleaner, mix up a batch of epoxy and cover the bottom side of the wells with the epoxi.

        I can post pics later if needed. (at work right now)

        Comment


          #5
          dmcb wrote:
          Rusty plugs raised my uh oh alarm.

          Where was the rust, on the outside or on the part in the engine?

          Doug
          ^

          Bingo. Those plugs should not be rusty. That means water in the cylinders.

          Time to do a compression test, and to look at your manifolds. Pull the plugs again to see if water comes out of the cylinders.
          Matt Train
          BOC Site Team
          Chicagoland, IL

          Comment


            #6
            +1 on the rusty plugs, that means moisture in the cylinders. If they are indeed rusty not electrically eroded. Run a compression check, all cylinders must be with in 5% of average reading and above 140 psi.

            Comment


              #7
              dmcb wrote:
              Rusty plugs raised my uh oh alarm.

              Where was the rust, on the outside or on the part in the engine?

              Doug
              Hi Doug,

              Rust was on the outside. . . thank heavens.

              The inside was a nice slightly rich, slightly sooty, rich chocolate brownie colour.
              Terry (Retired Diving Instructor and Part Time IT Consultant)
              1998 Bayliner 2452. 5.7l V8 - Edelbrock 1409 4bbl - Alpha1Gen2 - Solent UK.
              MMSI 235061726

              Comment


                #8
                my05hammer wrote:
                Have you had the carb off lately? The q-jet has a few inherent flaws. One of them being the fuel wells. These wells are where the jets for the primaries pick up fuel off the bottom of the fuel bowl. These wells have a bad tendency to leak as the carb ages. They are leaking so badly on my OMC that it has a very rough idle and the carb will need this repaired in the spring.

                One way to tell it they are leaking is just by starting it. If you let the boat set for a few days, does it pop right off when you try to start it? If it has to be cranked for a few times then the fuel bowl is most likely dry from leaking down.

                If this ends up being the problem, the way to fix this is to obtain a rebuild kit for the carb, pull the well plugs, press in the new ones from the kit, and then thourally clean the outside of the wells with carb cleaner, mix up a batch of epoxy and cover the bottom side of the wells with the epoxi.

                I can post pics later if needed. (at work right now)
                Hi,

                I was ordering a repair kit today. It is 5 years since I stripped the carb so I thought a strip down and clean must be called for. If you have some shots of the problem that would be very helpful please.

                Terry
                Terry (Retired Diving Instructor and Part Time IT Consultant)
                1998 Bayliner 2452. 5.7l V8 - Edelbrock 1409 4bbl - Alpha1Gen2 - Solent UK.
                MMSI 235061726

                Comment


                  #9
                  GrindKore wrote:
                  +1 on the rusty plugs, that means moisture in the cylinders. If they are indeed rusty not electrically eroded. Run a compression check, all cylinders must be with in 5% of average reading and above 140 psi.
                  Hi,

                  I did a compression test about 4 months back when looking for some unrelated overheating issue (caused by a bad outdrive repair). All cylinders are at a very regular 160 +/-2 or 3 PSI. The rust was on the outside of the plugs.

                  Many thanks

                  Terry.
                  Terry (Retired Diving Instructor and Part Time IT Consultant)
                  1998 Bayliner 2452. 5.7l V8 - Edelbrock 1409 4bbl - Alpha1Gen2 - Solent UK.
                  MMSI 235061726

                  Comment


                    #10
                    Rust on outside=OK.

                    Phew.

                    Doug
                    Started boating 1955
                    Number of boats owned 32
                    Bayliners
                    2655
                    2755
                    2850
                    3870 presently owned
                    Favorite boat. Toss up. 46' Chris Craft, 3870 Bayliner

                    Comment


                      #11
                      dmcb wrote:
                      Rust on outside=OK.

                      Phew.

                      Doug
                      Agreed. Quit giving us heart attacks here.

                      Next thing to check: Timing.
                      Matt Train
                      BOC Site Team
                      Chicagoland, IL

                      Comment


                        #12
                        TerryW wrote:
                        Hi,

                        I was ordering a repair kit today. It is 5 years since I stripped the carb so I thought a strip down and clean must be called for. If you have some shots of the problem that would be very helpful please.

                        Terry
                        When you get the kit there will be an instruction sheet that should have a parts diagram of the carb. There is a black heart shaped sponge that is installed between the bottom of the fuel bowl and the throttle plate. The fuel wells are what contact the top of the sponge when it is in place. These wells will have a plug that will be replaced during the overhaul. These plugs are what you will want to replace, and then epoxy with JB Weld.

                        Below is a pic of the bottom of the fuel bowl. The circled areas are the plugs needing epoxied. These plugs are where the fuel wells are for the four main jets.

                        .

                        Comment


                          #13
                          Many thanks for the picture. That really spells it out.

                          I await with anticipation for the rebuild kit to arrive. I ordered some marine JB weld as well.

                          Terry
                          Terry (Retired Diving Instructor and Part Time IT Consultant)
                          1998 Bayliner 2452. 5.7l V8 - Edelbrock 1409 4bbl - Alpha1Gen2 - Solent UK.
                          MMSI 235061726

                          Comment


                            #14
                            Hi Terry

                            That image doesn't look like the 2BBL carb fitted to mine, i might be wrong!!!! but i don't recognise it.

                            I have just rebuilt mine Terry send me an email if you need any pointers.

                            Regards.

                            Comment


                              #15
                              Hi dave,

                              It has been 5 years since I rebuilt mine. I can't remember what it looks like when it is pulled apart. I have the manual but as soon as I get into trouble I'll be straight on the phone.

                              My carb is a mercarb2 according to the manual. I don't know if that is the same as a 2BBL. I always thought they were the same but that is only guesswork.

                              Many thanks

                              Terry.
                              Terry (Retired Diving Instructor and Part Time IT Consultant)
                              1998 Bayliner 2452. 5.7l V8 - Edelbrock 1409 4bbl - Alpha1Gen2 - Solent UK.
                              MMSI 235061726

                              Comment

                              Working...
                              X