Coils grounding each other out

[Mithral 14]

So my Kohler CH18S had a coil problem.  One coil tested out bad.  So I replaced both coils while I have things apart, ... and now I have a coil grounding issue.

 

When the kill wire is connect to both coils, the engine will not start.

If I remove both kill wires the engine will start, and will consequently stop when I reconnect the wires.

If I remove one kill wire from either coil, the engine will start and run on one cylinder, until I reconnect the second kill wire and then the engine stops.

If I disconnect the kill wire going to the wire harness, it makes no difference to the above.

 

It appears that the kill wire connected in series from one coil to the other coil is grounding out from coil to coil.

 

I have no idea why this might be.  Unless I simply got the wrong coils.

 

So I thought I would ask advice before I go rewiring myself a separate kill switch while I have everything opened up.   Or I guess I could fall back to just choking it to turn off.  Hmm....

 

 

 

Edited June 5, 2020 by Mithral

[Achto 29,228]

2 hours ago, Mithral said:

It appears that the kill wire connected in series from one coil to the other coil is grounding out from coil to coil.

 

Your ignition switch should have a M terminal. This term should be wired to the kill terminal on the coils and should be grounded out when the switch is in the off position. When the switch is in the on position the M term and kill terms should not have continuity to ground.

 

 

[ebinmaine 71,792]

10 hours ago, Mithral said:

thought I would ask advice before I go rewiring myself a separate kill switch while I have everything opened up.   Or I guess I could fall back to just choking it to turn off.  Hmm

It would be better to fix it correctly so you know whatever is causing the current issue:

 

1. Let's you figure out what the ACTUAL issue is.

 

2. Isn't causing something else you don't know yet.

 

3. Doesn't cause difficulty in future repair.

 

 

What is the tractor?

 

Have you triple checked the existing wire/wires to verify one or more isn't pinched?

 

Is the ignition switch bad?

 

Where did you get the coils?

 

Did you, or they, verify the coils are correct for the actual application and NOT a universal part or worse yet, a guess?

 

Have you tried putting the coil that tested good back to see if the problem changes?

After you do that, switch sides with wires and coils to verify the problem changes again, or doesn't...

 

Putting a known good part back will tell alot.

[Mithral 14]

What is the tractor?  416-H.  But with retrofitted Kohler CH18.

 

Have you triple checked the existing wire/wires to verify one or more isn't pinched?  Yes.  Wires are all good given I just rebuilt the wiring harness with proper schematics.

 

Is the ignition switch bad?  Switch is new.

 

Where did you get the coils?  Aftermarket.

 

Did you, or they, verify the coils are correct for the actual application and NOT a universal part or worse yet, a guess?  -  I thought I bought proper replacement coils, BUT ... they were cheap, and I'm thinking I got generic universal parts.  Which I'm now thinking is the real problem.  

 

Have you tried putting the coil that tested good back to see if the problem changes?  Yes, but the other replacement coil is still a problem.

 

After you do that, switch sides with wires and coils to verify the problem changes again, or doesn't...  -  The problem remains as long as one or both of the replacement coils are in.

 

Everything seems to point to me getting the wrong coils, doesn't it?

 

[ebinmaine 71,792]

1 hour ago, Mithral said:

retrofitted Kohler CH18

 

I'd see if you have a GOOD small engine repair shop and get the coils based on the information from the engine. Not the tractor.

If you don't have a good reliable place locally to buy parts call Lincoln at A to Z Tractor in PA.

Give him the engine numbers.

 

1 hour ago, Mithral said:

Switch is new

 

One of the things I learned working in Auto parts is not to assume a new part is either correct or working properly.

 

Remove the new switch and carefully compare it to the old one. 

Verify position and letter markings next to the terminals.

If the new switch doesn't have the terminals marked ... DON'T USE IT. Because you can't verify a correct circuit.

 

 

1 hour ago, Mithral said:

Everything seems to point to me getting the wrong coils, doesn't it?

 

Certainly seems headed that way...

[Mithral 14]

So after posting this message, I found the following comments on another site (eBay) with reviews of these aftermarket coils:

 

These aftermarket coils work, however, electronically are quite different.The kill pin has too low internal resistance. In a dual cylinder engine, if two of these coils are replaced together, the engine will not start because the kill pin resistance, when two coils are in parallel, is below the starting threshold and the engine thinks it is in the kill mode. So the engine will not start. Using one coil in single coil engine, or one of this coil together with a genuine Kohler coil is ok. Kohler coil has much higher internal resistance so the combined resistance is outside the kill mode and the engine will start. But it will not work if you have to replace both coils.

 

Looks like I wasted a few $ to learn a lesson about cheap aftermarket parts.

 

 

Edited June 5, 2020 by Mithral

[ebinmaine 71,792]

9 minutes ago, Mithral said:

learn a lesson about cheap aftermarket parts

Many of us have been there, myself included.

[Mithral 14]

Its kinda sad because other than the low resistance of the kill pins the coils work just fine.