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1970 14 hp kohler no spark

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wayne huber
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PostPosted: Mon Nov 25, 2013 7:04 am    Post subject: 1970 14 hp kohler no spark Reply to specific post Reply with quote

my 1970's economy 14 hp kohler has no spark it has pointless ignition the wire from the stator to the a side of the trigger should that wire have power when you turn the key switch on ???
 
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Bob
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PostPosted: Mon Nov 25, 2013 10:16 am    Post subject: Re: 1970 14 hp kohler no spark Reply to specific post Reply with quote

The wire to the key switch is a "kill" wire and should NEVER have power from the ignition switch, or you will let the very expensive smoke out of the EI module.

The EI is self-powered by the action of the magnets on the flywheel and the coils on the stator behind the flywheel..

Troubleshooting info is in the Kohler factory manual at the link below: (.pdf format)
K series single cylinder

 
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Harvey2
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PostPosted: Mon Nov 25, 2013 12:44 pm    Post subject: Re: 1970 14 hp kohler no spark Reply to specific post Reply with quote

I also have a 1970 Power-King that had the breakerless igniton system.
When I found out how expensive the parts were I converted it over to battery ignition with points.
Usually when I work on a Briggs engine I switch them to electronic ignition, the price of a coil is less than points, condensor and the agravation of the points fouling.
I have several PKs to sell.
 
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joe csuti
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PostPosted: Tue Nov 26, 2013 7:55 am    Post subject: Re: 1970 14 hp kohler no spark Reply to specific post Reply with quote

As Bob said trigger module is powered by a seperate winding on alt stator & lead(s) to trigger module should only have AC voltage when cranking eng.

Before condeming trigger module/coil try a couple of things 1st.

Locate & disconnect ign kill lead to ign sw at Y/T connector close to ign coil connection,crank eng & check for spark,if you have spark now then problem in lead to ign sw,ign sw itself or safety sw's on tractor(if any).

If still no spark with kill lead disconnected,disconnect AC output leads from alt stator at rectifer/regulator,crank eng & check for spark,if you have spark now then problem in rectifer/regulator,depending on how tractor wired,if output from regulator is wired thru ign sw,if diode(s) in regulator shorted when ign sw turned on this will allow DC battery voltage to backfeed into alt stator & turn same into an electromagnet killing all AC voltage in alt stator.

If still no spark with kill lead/regulator disconnected,then download/save K series service manual at link provided by Bob & follow troubleshooting guide in sect. 8 of manual for solid state ign.
 
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wayne huber
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PostPosted: Wed Nov 27, 2013 11:43 am    Post subject: Re: 1970 14 hp kohler no spark Reply to specific post Reply with quote

Thanks guys for your feed back !! I went back and did the inspection as per the kohler service manual so I started at the stator I have 23 volts when cranking at the a terminal of the trigger mod . So I then bench tested the trigger itself it looks good as per the test then I did a bench tested the coil with a ohm meter witch seem to be good so I unhooked the kill wire from the switch and still no spark !! so I the took my test light and hooked to the connector at the bottom of the coil and I do get a dim light when cranking at the coil trigger wire. I really think its a bad coil !! but at $225.00 would like to be sure!!
 
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joe csuti
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PostPosted: Wed Nov 27, 2013 1:46 pm    Post subject: Re: 1970 14 hp kohler no spark Reply to specific post Reply with quote

Remove coil from eng & take with you,fri-sat check with several local mower shops to see if they have a coil tester that they can test coil with,some shops have a tester for this type coil,others don't.In the meantime if you haven't done so already,check plug lead with an ohmmeter,you might have a bad plug lead,also use a new plug for testing as old plug may be bad.

If local shop can test coil & same is bad,kohler online parts lists coil for $193 if that's any help.

One thing that confuses me in you reply,when you said you disconnected kill lead at sw,do you mean you disconnected kill lead where output from trigger module & coil join OR at ign sw itself?
 
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wayne huber
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PostPosted: Wed Nov 27, 2013 8:18 pm    Post subject: Re: 1970 14 hp kohler no spark Reply to specific post Reply with quote

unplugged the wire at the ignition switch to make sure my switch was not bad. and I did check the plug wire its good . I have a in line spark tester so I can see it flash when I get spark I have the coil with me so I can check with a few places to see if anyone has a coil tester. thanks again for your feed back!!!!
 
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Bob
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PostPosted: Wed Nov 27, 2013 9:42 pm    Post subject: Re: 1970 14 hp kohler no spark Reply to specific post Reply with quote

Interesting. IS there a machine out there that can definitively test this which, as you know, has diodes, a capacitor, and probably some other electronic components in it?
 
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joe csuti
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PostPosted: Thu Nov 28, 2013 3:02 am    Post subject: Re: 1970 14 hp kohler no spark Reply to specific post Reply with quote

Disconnect kill lead wire at junction of trigger module/coil also & check between each end of same with an ohmmeter unless you can see length of wire completely between eng connection/ign sw,wire may be grounded due to yrs of heat,vibration & rubbing against sheetmetal or brackets on tractor,if wire grounded it will give same result as turning ign sw to off/stop position even though kill lead disconnected from ign sw.
 
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joe csuti
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PostPosted: Thu Nov 28, 2013 4:05 am    Post subject: Re: 1970 14 hp kohler no spark Reply to specific post Reply with quote

Bob-I think you misunderstood my reply,I was speaking of coil which to my knowledge has no electronic parts in it except possibly an internal condenser as looking at diag on pg 8.4 in manual of trigger module the condenser is located down stream of kill sw & I know of no ext mounted condenser on this type of ign system & suspect condenser is internal in coil,this might also explain why manual only tells you how to check secondary of coil,but nothing about checking primary.

It's possible there are either old testers/newer testers running around out there to check trigger module operation without removing trigger from eng in addition many of newer kohler eng have smart spark system which have a pickup installed in coil,when this style coil is checked I don't know if different make/mod testers have provisions for checking pickup also when testing coil & possibly be backward looking to check trigger modules,it's been over 30 yrs since I've taken a coil to a shop to have checked so I don't really know what's out there now in the way of testers.
 
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Bob
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PostPosted: Thu Nov 28, 2013 7:34 am    Post subject: Re: 1970 14 hp kohler no spark Reply to specific post Reply with quote

Yep, no diodes, I see, but a capacitor in series with the primary winding. I wonder what the results are when checked with a Mercotronic... can it be tested as a normal coil with that capacitor in series?
 
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joe csuti
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PostPosted: Thu Nov 28, 2013 1:57 pm    Post subject: Re: 1970 14 hp kohler no spark Reply to specific post Reply with quote

If the the condenser is internal in coil which I more & more suspect,it probably serves the same function as a condenser in a normal points ign setup in that when points open a spike voltage up to 3 times supply voltage is generated for a fraction of a second as magnetic field in coil is collapsing,this spike voltage is induced into secondary winding of coil & boosts hv output,in addition spike also traveles back to source(points)the condenser across the points absorbs the spike voltage & reduces voltage in coil primary to as close to zero volts as possible before the next points cycle so you get max voltage buildup in primary of coil next time points close,in addition condenser prevents point burning/drawing an arc when points open,if condenser wasn't in circuit or if condenser open/shorted voltage would stay high in coil primary & have the effect of points staying open/closed all the time & no high voltage will be generated.

As far as solid state ign,I think the condenser in series with primary of coil is there to function as a buffer to protect scr in trigger so spike voltage from coil doesn't exceed piv voltage rating of scr,it may also function as a disconnect on load side of scr as usually when you use an scr in a DC circuit circuit when the scr turns on it will stay on an act as a latching relay till source voltage or load disconnected from scr so same can turn off,I found this out the hard way many yrs ago when I added foil defroster grid to rear window of my van,instead of buying a electro-mechanical relay I used a 20A solid state sw I had on hand,I killed battery in van 3 times in 2 days & couldn't figure out why,came to find out soild state sw was staying on/latched & powering defroster grid all the time after solid state sw turned on,even though sw on dash for sw turned off,only way to turn sw off was to disconnect load/supply voltage for a second or two.

As far as checking coil with a normal coil tester designed for 12v coils I don't know,it's something that would have to be tried,with condenser in series with coil primary if condenser open tester wouldn't work on coil,if condenser shorted it may give a false indication as to condition of coil or if coil working correctly,the only way I can think of to test solid state coil is to take a know good coil & see how/if it works with tester & use that as a standard when checking other coils.

Years ago I gave a thought to building a tester for trigger module/coil,however since that time either I no longer have engines with solid state ign or converted same to point ign as solid state systems went bad,just converting is an adventure in itself.
 
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Bob
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PostPosted: Thu Nov 28, 2013 4:03 pm    Post subject: Re: 1970 14 hp kohler no spark Reply to specific post Reply with quote

Actually, I believe the capacitor in those Kohler EI coils gets charged voltage from the stator that gets rectified by diode(s) in the trigger module, and when the SCR is triggered it discharges the capacitor through the coil and makes the spark, a primitive CD ignition system.
 
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joe csuti
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PostPosted: Thu Nov 28, 2013 7:18 pm    Post subject: Re: 1970 14 hp kohler no spark Reply to specific post Reply with quote

You may be right,I've never put a trigger module on bench & tried to do open heart surgery on it & figure out how it works,what does strike me as strange is condenser is non polarized,I would think same would have to be polarized to operate correctly in a cd system,but I may be/am probably wrong,it just may be another one of those mysteries of life/electronics.
 
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Bob
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PostPosted: Thu Nov 28, 2013 10:01 pm    Post subject: Re: 1970 14 hp kohler no spark Reply to specific post Reply with quote

HOW do we know the capacitor that's epoxied inside the coil is NP?

I've got a bad coil lying on the back of the bench somewhere... I'll try to find it and dissect it some cold and stormy day this winter when it's too cold to do much else!
 
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