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  1. #1

    Join Date
    Aug 2012
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    7
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    Florida
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    MTD - Yard Machines

    Briggs and Stratton 18 hp Twin II not getting spark

    I have a MTD lawn tractor with a Briggs and Stratton 18 hp twin II engine. I'm not getting any spark to the plugs. I know there are safety switches but I don't know where they are at. I know there is supposed to be one at the seat and one at the brake but I don't know where. This is approx 2002 tractor - 42" cut, B&S model number 42A707. Thanks for any help in advance!

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  3. #2

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    kioti/rhino finish mower

    Re: Briggs and Stratton 18 hp Twin II not getting spark

    Remove the blower housing, and unplug the wire going to the ignition module. Crank engine and see if you have spark. If no spark, replace the module. If you have spark with the wire unplugged then check the clutch switch, located either under the frame next to the rod for the brake, or just inside the dash housing between the steering rod and the engine on the left side on top of frame. The pto switch which is located most likely under the transmission tunnel between your legs if sitting on seat, if not electric clutch. I think you know where the seat switch is located.

    The PTO and clutch switch most likely prevent cranking in the first place, but have seen stranger things. If iswitches check out then you will have to look for bare wires, or shorts in the kill circuit. Mice have a tendency to chew the insulation off of the kill wire under the blower housing causing shorting of the kill wire to the sheet metal.

    I hope this helps.
    ILLINOIS ENGINE, BEECHER CITY, IL
    BRIGGS AND STRATTON MST (MASTER SERVICE TECHNICIAN)
    Sales and Service for Dolmar/Makita, Poulan, Briggs and Stratton, Kohler, Lauson(Tecumseh, LCT), Generac, Brute, Honda, Subaru
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  4. #3

    Join Date
    Aug 2012
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    Florida
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    MTD - Yard Machines

    Re: Briggs and Stratton 18 hp Twin II not getting spark

    Quote Originally Posted by ILENGINE View Post
    Remove the blower housing, and unplug the wire going to the ignition module. Crank engine and see if you have spark. If no spark, replace the module. If you have spark with the wire unplugged then check the clutch switch, located either under the frame next to the rod for the brake, or just inside the dash housing between the steering rod and the engine on the left side on top of frame. The pto switch which is located most likely under the transmission tunnel between your legs if sitting on seat, if not electric clutch. I think you know where the seat switch is located.

    The PTO and clutch switch most likely prevent cranking in the first place, but have seen stranger things. If iswitches check out then you will have to look for bare wires, or shorts in the kill circuit. Mice have a tendency to chew the insulation off of the kill wire under the blower housing causing shorting of the kill wire to the sheet metal.

    I hope this helps.
    We want to tell you that we really appreciate your help. We went from thinking it was a fuel problem to it involved an ignition problem instead. Your original response to the carberator/fuel problem was appreciated. Well it turned out that your first sentence in my question about the spark problem was the key.....Thank You!!! I replaced the module. The guy that I've been talking to here told me that this is the most common problem to this model. I can't thank you enough for your help. I was so puzzled I lost sleep. I can usally fix anything so I really needed input. I mowed my lawn tonite!! I will seek your help in the future if I have a problem. Hopefully.....I'm good. God Bless

  5. #4

    Join Date
    Sep 2016
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    Ontario
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    Wheel Horse

    Re: Briggs and Stratton 18 hp Twin II not getting spark

    Hello-am new to the sight but enjoy working on my own engines-recently had the same issue as mrduck with no spark to the plugs,checked all the switches and bypassed temporarily no difference.Read the advice from ILengine and unhooked the ignition module-no spark.I will be at the lawnmower shop in the morning for a new module hopefully this will fix the problem.

    My lawn tractor is a 25 year old Wheelhorse looks like new and bought new by me.Tks for the great advice.Gord

  6. #5

    Join Date
    Sep 2016
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    Location
    Ontario
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    Wheel Horse

    Re: Briggs and Stratton 18 hp Twin II not getting spark

    Hello again-I picked up a new voltage regulator today and installed it but still no spark at the plugs-cost me 100 dollars for a new regulator-on ebay 22 dollars-but at least I have a spare.
    Anyhow the owner of the lawnmower shop told me the voltage regulator had nothing to do with having no spark on my 16hp Vanguard OHV twin.He told me it also was unlikely that both coils went bad at the same time so he figures its the resistor wire connected between the two coils.
    My question is does this sound right and is there a way of testing the resistor wire??Tks for any help.Gord

  7. #6

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    Re: Briggs and Stratton 18 hp Twin II not getting spark

    Always a problem when you piggy back on an old thread.
    The regulator /rectifier has nothing what so ever to do with the ignition.
    Undo the wire that connects the two coils together and undo the wire that connects the ignition modules to the mower.
    In this situation you will need to be able to ground out both the coils to stop the engine if it starts.
    The little black wires ground the coils to turn them off the ignition switch breaks the ground contact to turn them on.
    The chip in the coil measures the tiny voltages being generated as the magneto coil just starts to generate to work out when to fire the plug.
    The ripple effect means one coil firing will interfere with the second coil so there is a DIODE between the two of them.
    The diode can go bad and that will cause erratic sparking of the second coil.

  8. #7

    Join Date
    Sep 2016
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    Ontario
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    Wheel Horse

    Re: Briggs and Stratton 18 hp Twin II not getting spark

    Thanks bertsmobile1 for all the great info-yesterday I went back over all the wiring and switches in case I had missed something simple.Lo and behold where the kill switch attaches to the fan shroud I found the nut loose and the one black wire grounding on the case.
    I tightened the nut and first turn the engine was running.Anyhow as a newbe to this site it is great to get some help when a person gets stuck.Tks againGord

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