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John Deere D100 - No Spark
My friend has a D-100 two cylinder (likely a Home Depot model) that died after it was parked.
No spark from either plug. I cannot find a schematic online. It has twin coils with diodes that go to ground (I think), I would expect this to be grounded to kill the engine? No manufacturers name on the engine. Might be Briggs and Stratton? A schematic would point me in the right direction to figure out why both coils have failed. Anybody have any suggestions?
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06-29-2016, 03:03 PM
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Pull the kill wires off each of the coils(at the coil) and see if it sparks.
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Don 1988 Targa |
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06-29-2016, 03:19 PM
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Pulled one off, broke it and stopped. Still no spark from the one I took off...
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06-29-2016, 03:29 PM
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Pull both off. How are you checking spark?
Also, some have a low oil sensor that won't allow spark if the oil is low, but pulling the diode wires eliminates that. Post a pic of the motor so we know what you're dealing with.
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Don 1988 Targa Last edited by Red88Carrera; 06-29-2016 at 03:37 PM.. |
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06-29-2016, 03:31 PM
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I'm just grounding the plug to the case. No blue spark.
I will get a picture if it doesn't start. Since I unplugged the one coil I should have got a spark there...
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06-29-2016, 03:47 PM
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Yep, if you unplug the kill wire from either coil, that coil should spark. Have you tried new plugs?
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Don 1988 Targa |
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06-29-2016, 03:49 PM
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I have not tried new plugs, but since they both died at the same time it has to be something else...but all I can think is the flywheel magnet died...what else is there in common?
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06-29-2016, 03:51 PM
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I have seen both plugs fail to fire at the same time.
The only way for the flywheel magnet to fail is if it let loose from the flywheel. I'm assuming this is electric start. Make sure there is a good ground between the engine block and the battery.
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Don 1988 Targa |
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06-29-2016, 03:55 PM
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Riding mowers have numerous "cutout" switches that will kill spark....Seat, blade engage, reverse, etc.
Run a jumper wire straight from your battery positive to where your engine gets it voltage.
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06-29-2016, 03:59 PM
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weekend wOrrier
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+1 For the oil pressure cut off switch.
LOL on the other cutoff switch(es). I remember buying my JD and trying to unload it from the delivery truck. Every time I got off the seat to see why it kept cutting off, it would- CUT OFF!!!!! THE FIRST THING TO GET BYPASSED WAS THE SEAT CUTOFF!!!!! Last edited by LEAKYSEALS951; 06-29-2016 at 04:32 PM.. |
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06-29-2016, 03:59 PM
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Quote:
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Don 1988 Targa |
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06-29-2016, 04:00 PM
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I am thinking two things: poor ground on the plug when I tested them and low oil.
I will report back, thanks for the suggestions.
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06-29-2016, 04:53 PM
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weekend wOrrier
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I like the suggested idea of disconnecting the ground line from the magnetos.
That confirms they are good, and something else is shorting it. Then it's just a matter of confirming what is shorting it. As for the oil pressure cutoff... perhaps low oil. I would think the oil if ok, but switch itself is frozen shut from disuse. Also, longshot- oil pump intake/line itself is clogged from disuse, Interesting stuff, these little engines. Also? was ignition switch changed at any point. Wrong type reinstalled could spell trouble. They look the same from outside, but there is a huge difference between the coils and magneto type switch internals.(another longshot) updates please! Last edited by LEAKYSEALS951; 06-29-2016 at 06:20 PM.. |
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06-29-2016, 06:16 PM
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Again, disconnecting the kill wires from the coils will eliminate everything ahead of it.
I have a 16hp Briggs twin making close to 50hp. This is my favorite motor, so I know a little about it.
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Don 1988 Targa |
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06-29-2016, 06:29 PM
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Still Doin Time
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50hp?? Please tells more / possibly new thread.....
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06-30-2016, 02:29 PM
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40 shot of nitrous...
I've been sent to sunny California for work. I doubt I can update this thread before next week.
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06-30-2016, 04:05 PM
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Bland
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I just finished rewiring our JD mower last night. There are no more safety switches, you turn the key, it starts.
Previously, there were safety switched for the pto, seat, clutch, etc... The connections are corroded and I was tired of screwing with it constantly... The wire going to the coils should never have positive voltage hooked up to it, it will melt down... You ground this out to kill the spark - my notes in the top left are incorrect in this regard...  This is what happens if you hook up 12v to the coil...  Also, arns equipment is cheaper and better to deal with than EJ Mower and can get you aftermarket parts.
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06-30-2016, 04:51 PM
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He pulled the ground from both coils over the weekend, now the starter won't engage...
I need to go have another look when I get home. Curiouser and curiouser. I think I will pull the coil grounds and hot-wire the starter solenoid when I go back there.
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07-04-2016, 12:13 PM
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Just to be clear...
The wire going to the coil is not the coil ground. The coils are grounded to the engine casing, which is grounded to the battery. The wire going to the "Magnetron" coil is for the ignition kill circuit. Grounding that wire will kill the coil, and shut down the engine.
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Don 1988 Targa |
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07-04-2016, 01:26 PM
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This is what I was referring to....
 There is only one connection on each coil, it's a ground wire (I think) that kills the spark. There are two (since it's a two cylinder) and the ground from each has been removed.
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07-04-2016, 01:51 PM
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Crop Duster
Kachow
1976 Porsche 930
