Msd issues???
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Msd issues???

  1. #1
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    Default Msd issues???

    So this past weekend we had a major gremlin working against us in our drag boat. Saturday morning we warm the boat up and get put in the water for 1st run of test n tune Boat runs 7.54 @108 mph straight off the trailer No issues ran fine. Come back and put fuel in the boat. Go back out for another pass. Boat is hard to start on the rope. Put in gear and mash the gas, falls on its face and won’t rev at all. Spits and sputters down the track. We put a new msd box, coil, crank trigger sensor and trigger wire. Went back in the water and did the same thing. Won’t pull any rpms We know it’s not on the fuel side of things. We have pressure at the regulator and also put a new fuel pump in just to make sure. Sunday morning after the boat has sat all night. We go and make a test pass. Boat runs 7.65 @109 mph. Runs fine. Go back and make another pass and boat does exactly the same thing. Falls on its face and won’t pull any power. We’ve checked the power supply and grounds. Basically replaced everything besides front mount distributor. But checked cap and rotor. Prior to this the boat has been just fine

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    What kind of box, and coil? Are there any rev limiting boxes?

    Grounds are good?

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    Msd 7ml2 box. Msd pro power coil Had an 8000 chip for rev limiter. Motor spun 7400 on tach recall. We don’t run an alternator but charge battery between every round. Running optima red top We swapped the marine box for a non marine box that we had in the trailer just to see if box was the issue

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    It's a long shot, but check the air bleeds to make sure there is not a bug or something in them. The high speed is where I would start.
    It sounds crazy, but it happened to me.

    A good flash light will let you see if there is a problem there.

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    Senior Member ol guy's Avatar
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    sounds like a ground issue to me. Only shows up after warmed up or HOT. To be honest I am not very educated on MSD but I do know they are VERY touchy about their grounds, which is why I wont run one. MLAO

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    With aluminum heads I always run grounds from each head to the negative side of the battery.

    Paul

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    Different rpm chip?
    Originally Posted by gn7 "Stick to making the worlds best engine stand."

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    A friend has a 588 inch BBC Blower motor in a Daytona Eliminator. Has had nothing but problems with MSD boxes. One time runs perfect. Next time breaks up backfires and runs like SHIT!!!After replacing the MSD box three times he finally got one that works. The quality control must be ZERO!!!Click image for larger version. 

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    perhaps you are getting heat soak issues with a sensor? Does MSD have an intake air temp sensor? In the auto tuning world, we usually disable open-loop sensor readings for 30 seconds after hot restarts to keep it from running super lean. I'm not sure what all the MSD requires but I would guess it's a sensor.

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    Always try the cheapest thing first. Change the battery.
    I don't know what I don't know because I forgot !!!

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    are you using the side terminals on that red top, or the top posts?

    it very much sounds like a loose connection somewhere. I've had the same thing happen at the world finals in 2004. go through the boat, and see if anything has loosened even a little bit. check it with a wrench. make sure all connections are clean. a loose ground or power wire, even if it doesn't "look" like it's loose at all, can cause you fits. these boxes either work or they don't. there is very little in between, and the in between is usually caused by a faulty ground or a loose connection somewhere. the fact that you could get down the track the 3rd time makes me believe it's not the box at all.

  14. #12
    Lookout I'm Crankin it Baby Rattle Can Lou's Avatar
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    Quote Originally Posted by bp298 View Post
    are you using the side terminals on that red top, or the top posts?

    it very much sounds like a loose connection somewhere. I've had the same thing happen at the world finals in 2004. go through the boat, and see if anything has loosened even a little bit. check it with a wrench. make sure all connections are clean. a loose ground or power wire, even if it doesn't "look" like it's loose at all, can cause you fits. these boxes either work or they don't. there is very little in between, and the in between is usually caused by a faulty ground or a loose connection somewhere. the fact that you could get down the track the 3rd time makes me believe it's not the box at all.
    This is exactly what I've been told..if the box is bad...its bad...like no workie. In our case it was Alt not wired correctly...and it caused a drop in voltage...that was all it took. Almost a summer of lost fun over that..

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    Senior Member jockorace's Avatar
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    One word.........................MAGNETO!! Jocko

  16. #14
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    If MSD products are wired correctly, They rarely miss a beat. When you say grounds, that is not good. One ground should be used. nothing grounded to aluminum. also, check your ignition switch and kill switch. Battery voltage as mentioned above is key. Also, some batteries have internal issues as well so take the battery out and check it for internal shorts. The rotor tab usually has to be bent upward to the required dimension that MSD calls out. They come in the package bent down. We have been putting these in boats for over 30 years and had very few problems , and if we did , it was self inflicted .

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