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MSF30B 2012 No or intermittent spark

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  • MSF30B 2012 No or intermittent spark

    Hello,
    I've been searching and reading post after post for weeks now, all diagnostic references and testing procedures etc I can find and cannot figure this one out.

    I purchased a 13' mini speed boat about a year ago which has the Tohatsu 30 efi 4 stroke. It always started so easily. The boat sat for about 2 months and I went to go take it out and it would not start. I found it had no spark in any of the 3 cylinders. I checked the kill switch, was not the problem. I gave up after about 20 minutes as I had better things to do that day and decided Id take another, more professional, stab at it in the morning.

    The next morning I pulled the cord once and it started. Took the boat out on the lake and ran it on and off for the next 3 hours. No problems at all. Put the boat away that evening and attempted to take it out the following afternoon... No spark. that was 4 weeks ago and it hasn't run since.

    So here's where I'm at. I've followed my shop manual and tested all resistances. From what I'm seeing, they are all within spec. I made a DVA, pulses are all in spec.

    When it seldom gets spark, while cranking, the buzzer horn sounds. It always had done that since I owned it on every pull until it started, like a short whistle. Once started the horn shuts off. So now, every once in a while the horn will sound while trying to start it. At that time, if I have my spark tester hooked in line, it will light up on that pull. Next pull, and several pulls after, there will be nothing. Then it will have spark on one pull again, sometimes two.

    The only thing I'm finding strange in my testing's are, in the shop manual, there's a resistance test that is for the ignition coils. It shows testing from the, i.e. Black/white wire to the black, which shows resistance just out of spec on all three coils and the next test shows a resistance reading through the plug wire to the black ground. I'm not getting any reading on that test on all three coils, which leads me to believe I'm doing something wrong because I find it hard to believe all 3 of my ignition coils would fail simultaneously. Is that possible, but then all three suddenly light up on one pull, then for anywhere from 5 pulls to 50 pulls they're all dead again?

    I'm frustrated and ready to put a for sale sign on it. it seems, because of how its acting, it would be something simple. I've tried the jiggle test, ready to try the gentle persuader (hit it with a hammer) test.... For the life of me I cannot solve it.

    Thanks for any input or thoughts

    Scott





































  • #2
    I'd check the key assembly for issues. But it sounds like the computer is Doing it. I know if you try and start a four stroke with the engine tilted all the way up it will kill it and you have to turn off all battery juice and the back on to start... reset cpu... But it sou ds like I'd test out all the components that send a kill signal. Like the temp.. most of them when triggered send a ground signal..

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    • #3
      Thank you for the quick reply. I should have added a few more notes...

      Engine is the pull start only model, no key switch and does not require a battery. It does however have side mount throttle control, I've also disconnected the kill switch within the side mount box and went back to the kill switch on the front of the lower cowl.

      I've also done the "no no" of throwing a few parts at it, a temp sensor and an oil sensor. The temp sensor, although I did not test before replacing, looked nasty and I figured Id just replace the oil sensor while at it. Both easy and inexpensive.

      I too was leaning towards the ECU. I'm not sure what else to check as for the ignition kill circuit. I've chased wiring to no end. I've cleaned and checked the wire on the one ground I can find that installs behind the top right mount bolt that holds the plastic "tray" at the front of the engine.

      I also, although I believe not related, checked the TPS while going through the diagnostics in order in the shop manual and was only getting one of the three readings I should have. I tested it multiple times with the same results. I un-installed the sensor and checked it again on the bench and suddenly it read correctly on all three tests. It said it could be checked "with out removing parts" but I ran out of daylight and umph so I haven't got it re-installed yet to re-check.

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      • #4
        While it is possible that the ECU is failing, I've never had one quit. Remember that you need a good analog ohm meter to check resistances; It is normal for the coil secondaries to be to high in resistance that your meter sees that as an "open". If/when one fails, it usually goes shorted. Are you using the Factory service manual for a guide? If so, you can also test the ECU. Is there any chance that the oil is over full, even a drop? Temp and oil pressure sensors don't kill the ihgnition; rather they will limit RPM. There is a kit that your dealer may have, that allosw a laptop to connect to the ECU, and see the memories, as well as drop out ignition per cylinder, and drop out injectors per cylinder. Yes, if the TPS sensor is goofed-up, you can get weirdness. I would definitely revisit that. On the fuel side, remember that any time the motor will sit for a month or more, it's prudent to drain the vapor separator... but since the ignition seems to be the problem, I would definitely disconnect the brown wire from the kill switch, to make 100% sure that nothing is grounding it. If you are planning to test the ECU -- it gets pretty incolved -- remember that your ohm meter must be 3v or less; using a 9v meter could cook the ECU.
        Paul
        Buffalo NY USA

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        • #5
          If it's an all or nothing deal, where you have spark on all cylinders or you don't, it's highly unlikely 3 coils are going out or working at the same time. Safe bet eliminating the cols as your potential culprit.

          You can temporarily bypass/eliminate the temp and low oil pressures inputs from the ECU to rule those and associated wiring out of potential causes.

          That leaves the ECU or a ground/wiring harness issue.

          I'll share that I had an ECU that was just weak chasing my tail for 3 seasons. Yes 3 SEASONS! It was completely erratic, spark or no spark, but was most likely to fail if I had plans for others to join me. The following day, stuff all dragged out to troubleshoot, it would spark fine. I even removed the entire wiring harness at one point so I could inspect every inch of every wire, then re-taped it! Completely frustrated, I bit the bullet for the ECU, which fixed it permanently.

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          • #6
            Thank you all for the replies. Here's the latest...

            So I pulled the plugs, again, to make cranking on it easier. Spark tester hooked up. It sparks, along with horn sound, significantly more w/ plugs out than in.. or so it seems. I got tired of pulling and trying to figure out how to hold meters etc by myself so I removed the pull start and found the appropriate socket and began drill spinning it. I noticed when I pushed on wiring along side the port side of the engine it seemed to like to spark more than not.. coincidence? I'm thinking yes. because it wasn't consistent enough IMO. However, if I pushed the ground on the pulser coil on that side it really seemed to help. So, I removed, cleaned and reinstalled the ground wire. I spun it about 10 brief times with the drill and it horn sounded almost every time, as well as spark tester lit up. So, I reinstalled the pull start. Pulled it once.. no horn sound or spark in spark tester. Pulled it twice, same thing.. third pull, rope broke.... I removed the pull start and tried it with drill and cranked it about 30 times and couldn't get spark once.

            Ahicks, I replaced both the temp and oil sensors. What is the bypass procedure, just for giggles?

            thank you all for the help so far. I'm determined to figure this out.

            theres also an ECU for this motor on ebay, I'm tempted to purchase it but hate to just throw parts at it. I do not have a lap top and my local marina does not have tohatsu parts readily available so the hook up to test further is not an option unless I find and purchase it online... then I have to buy a laptop....

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            • #7
              Neither the temp nor oil sensor will kill ignition.
              Paul
              Buffalo NY USA

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              • #8
                Engine could have a hidden open cable between the sleeve and small plate holder that isecures it to timing plate if engine happens to have one. Constant cable flexing there when throttling will eventually break and give elctrical issues which will drive anyone crazy. Check with meter set at Ohm if exciter and pulser coils reads well or springs back to life when cables are wiggled around. Just my 1/2 cent theory...

                Happy Boating


                Sea Rider 320, 380 Sibs, 450 Rib, 2 Strokes Tohatsu 5,18 & 30 HP Proud Smokers

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                • #9
                  No timing plate. Advance is programmed in the ECU.
                  Paul
                  Buffalo NY USA

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                  • #10
                    Sign up today
                    Originally posted by Tiqueman View Post
                    Thank you all for the replies. Here's the latest...

                    So I pulled the plugs, again, to make cranking on it easier. Spark tester hooked up. It sparks, along with horn sound, significantly more w/ plugs out than in.. or so it seems. I got tired of pulling and trying to figure out how to hold meters etc by myself so I removed the pull start and found the appropriate socket and began drill spinning it. I noticed when I pushed on wiring along side the port side of the engine it seemed to like to spark more than not.. coincidence? I'm thinking yes. because it wasn't consistent enough IMO. However, if I pushed the ground on the pulser coil on that side it really seemed to help. So, I removed, cleaned and reinstalled the ground wire. I spun it about 10 brief times with the drill and it horn sounded almost every time, as well as spark tester lit up. So, I reinstalled the pull start. Pulled it once.. no horn sound or spark in spark tester. Pulled it twice, same thing.. third pull, rope broke.... I removed the pull start and tried it with drill and cranked it about 30 times and couldn't get spark once.

                    Ahicks, I replaced both the temp and oil sensors. What is the bypass procedure, just for giggles?

                    thank you all for the help so far. I'm determined to figure this out.

                    theres also an ECU for this motor on ebay, I'm tempted to purchase it but hate to just throw parts at it. I do not have a lap top and my local marina does not have tohatsu parts readily available so the hook up to test further is not an option unless I find and purchase it online... then I have to buy a laptop....

                    Not being familiar with your engine, I was speaking just generally. Without seeing the wiring diagram, anything I told you would be just a guess. I can tell you for sure it IS possible.

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