Riding Mower (Kolher engine) problem UPDATED - Changed out Ignition Coil and success!

[wkpoor]

Don't know if the OP said what kind of ignition system it has but unless its a fairly old one it will have a module and no points.
If it has points the condenser is there to stop the flow of current in the primary coil windings cleanly thus resulting in current flow in the secondary windings and a spark across the plug gap. When the points open the condenser begins to charge and when its fully charged current flow is stopped. That happens in a millisecond and is called the capacitance time constant. Hope that explains basic ign better than the condenser soaks up voltage.
Checking for spark in free air should be done with an increased gap to simulate compression. This is easily done with 2 points set 3/8-1/2 inch apart in a phenolic block. And as Jags said do as soon as the engine quits to see if it stopped do to loss of ign.

 

[Jags]

For the record the motor was said to be 12 yrs old. I am not sure when the cutoff from points to electronic occurs in the Briggs.

 

[ironpony]

o.k. lets really simplify this


Most four-stroke engines have used a mechanically timed electrical ignition system. The heart of the system is the distributor. The distributor contains a rotating cam driven by the engine's drive, a set of breaker points, a condenser, a rotor and a distributor cap. External to the distributor is the ignition coil, the spark plugs and wires linking the distributor to the spark plugs and ignition coil. (see diagram Below)

The system is powered by a lead-acid battery, which is charged by the car's electrical system using a dynamo or alternator. The engine operates contact breaker points, which interrupt the current to an induction coil (known as the ignition coil).

The ignition coil consists of two transformer windings sharing a common magnetic core—the primary and secondary windings. An alternating current in the primary induces alternating magnetic field in the coil's core. Because the ignition coil's secondary has far more windings than the primary, the coil is a step-up transformer which induces a much higher voltage across the secondary windings. For an ignition coil, one end of windings of both the primary and secondary are connected together. This common point is connected to the battery (usually through a current-limiting ballast resistor). The other end of the primary is connected to the points within the distributor. The other end of the secondary is connected, via the distributor cap and rotor, to the spark plugs.



Ignition Circuit Diagram - Mechanically Timed Ignition

The ignition firing sequence begins with the points (or contact breaker) closed. A steady charge flows from the battery, through the current-limiting resistor, through the coil primary, across the closed breaker points and finally back to the battery. This steady current produces a magnetic field within the coil's core. This magnetic field forms the energy reservoir that will be used to drive the ignition spark.

As the engine turns, so does the cam inside the distributor. The points ride on the cam so that as the engine turns and reaches the top of the engine's compression cycle, a high point in the cam causes the breaker points to open. This breaks the primary winding's circuit and abruptly stops the current through the breaker points. Without the steady current through the points, the magnetic field generated in the coil immediately and rapidly collapses. This change in the magnetic field induces a high voltage in the coil's secondary windings.

At the same time, current exits the coil's primary winding and begins to charge up the capacitor ("condenser") that lies across the now-open breaker points. This capacitor and the coil’s primary windings form an oscillating LC circuit. This LC circuit produces a damped, oscillating current which bounces energy between the capacitor’s electric field and the ignition coil’s magnetic field. The oscillating current in the coil’s primary, which produces an oscillating magnetic field in the coil, extends the high voltage pulse at the output of the secondary windings. This high voltage thus continues beyond the time of the initial field collapse pulse. The oscillation continues until the circuit’s energy is consumed.

The ignition coil's secondary windings are connected to the distributor cap. A turning rotor, located on top of the breaker cam within the distributor cap, sequentially connects the coil's secondary windings to one of the several wires leading to each cylinder's spark plug. The extremely high voltage from the coil's secondary -– often higher than 1000 volts—causes a spark to form across the gap of the spark plug. This, in turn, ignites the compressed air-fuel mixture within the engine. It is the creation of this spark which consumes the energy that was stored in the ignition coil’s magnetic field.

 

[stejus]

This should clear up the electrical comments out here. I have the service manual and pulled this for my CV14 Engine.

CV11-15, CV460-465, CV490-495 engines are
equipped with a dependable electronic magneto
ignition system. The system consists of the following
components:
• A magnet assembly which is permanently affixed
to the flywheel.
• An electronic magneto ignition module which
mounts on the engine crankcase.
• A kill switch (or key switch) which grounds the
module to stop the engine.
• A spark plug.


As the flywheel rotates and the magnet assembly
moves past the ignition module, a low voltage is
induced in the primary windings of the module. When
the primary voltage is precisely at its peak, the primary
circuit is interrupted, inducing a high voltage in the
secondary windings. This high voltage creates a spark
at the tip of the spark plug, which ignites the fuel-air
mixture in the combustion chamber.
The timing of the spark is automatically controlled by
the module. Therefore, other than periodically
checking/replacing the spark plug, no maintenance,
timing, or adjustments are necessary or possible with
this system.

 

[ironpony]

or magneto system for you aircraft guys

The simplest form of spark ignition is that using a magnet. The engine spins a magnet inside a coil, or, in the earlier designs, a coil inside a fixed magnet, and also operates a contact breaker, interrupting the current and causing the voltage to be increased sufficiently to jump a small gap. The spark plugs are connected directly from the magneto output. Early magnetos had one coil, with the contact breaker (sparking plug) inside the combustion chamber. In about 1902, Bosch introduced a double-coil magneto, with a fixed sparking plug, and the contact breaker outside the cylinder. Magnetos are not used in modern cars, but because they generate their own electricity they are often found on piston-engined aircraft engines and small engines such as those found in mopeds, lawnmowers, snowblowers, chainsaws, etc. where a battery-based electrical system is not present for any combination of necessity, weight, cost, and reliability reasons.

Magnetos were used on the small engine's ancestor, the stationary "hit or miss" engine which was used in the early twentieth century, on older gasoline or distillate farm tractors before battery starting and lighting became common, and on aircraft piston engines. Magnetos were used in these engines because their simplicity and self-contained operation was more reliable, and because magnetos weighed less than having a battery and dynamo or alternator.

Aircraft engines usually have multiple magnetos to provide redundancy in the event of a failure. Some older automobiles had both a magneto system and a battery actuated system (see below) running simultaneously to ensure proper ignition under all conditions with the limited performance each system provided at the time.This gave the benefits of easy starting (from the battery system) with reliable sparking at speed (from the magneto).

 

[Jags]

Primary and secondary windings speak of "coil". Please see my prior post.

You can chase this thing from a hundred directions till the cows come home. My simple spark test will eliminate at least 50% of possible problems (and cost you nothing but a few moments of time).

 

[ironpony]

Primary and secondary windings speak of "coil". Please see my prior post.

You can chase this thing from a hundred directions till the cows come home. My simple spark test will eliminate at least 50% of possible problems (and cost you nothing but a few moments of time).

agreed
spark and fuel = runs
one is missing

 

[stejus]

OK all here's the lastest after 24 hours since it last died...

Started engine on first turn and it ran for about 20 minutes.
I immediately tried to start and starter was turning the flywheel but it would not fire.
I pulled the sparkplug boot and put a plug in and grounded it to the block.
I tried to start it and there was no spark.

I am waiting for a while for the engine to cool and then try to get spark on the grounded plug.

 

[Jags]

I tried to start it and there was no spark.

For clarification - are you saying that when the spark plug was grounded and the motor turning over, there was no spark at the spark plug?

 

[basod]

COIL COIL COIL

 

[Jags]

COIL COIL COIL

Yep, yep, yep.

 

[basod]

sorry after reading through the finer points (no pun intended )of the whole magneto/coil(s) discussion above I was staring to wonder if Stejus was trying to troubleshoot his Kohler or understand how it worked.

 

[stejus]

I tried to start it and there was no spark.

For clarification - are you saying that when the spark plug was grounded and the motor turning over, there was no spark at the spark plug?

What I mean is I pullled the boot off the plug that is still screwed into the cylinder head. I then plugged another plug into the boot that was not installed but rather just resting on the block so it was grounded. I should see the sparkplug "sparking" but it wasn't.

 

[Jags]

I tried to start it and there was no spark.

For clarification - are you saying that when the spark plug was grounded and the motor turning over, there was no spark at the spark plug?

What I mean is I pullled the boot off the plug that is still screwed into the cylinder head. I then plugged another plug into the boot that was not installed but rather just resting on the block so it was grounded. I should see the sparkplug "sparking" but it wasn't.

Perfect.

Coil.

 

[stejus]

OK all here's the lastest after 24 hours since it last died...

Started engine on first turn and it ran for about 20 minutes.
I immediately tried to start and starter was turning the flywheel but it would not fire.
I pulled the sparkplug boot and put a plug in and grounded it to the block.
I tried to start it and there was no spark.

I am waiting for a while for the engine to cool and then try to get spark on the grounded plug.

Ok, just to add more testing I let the engine cool and then I tried to start it with the plug resting on the block so I could see spark. I saw spark so then I plugged the boot into the sparkplug installed on the cylinder head. I tried to start it and it turned over and fired up the engine.

So, everyone is thinking coil. I assume you are talking about the electronic magneto ignition module, right? I'll confirm I don't have any frayed wires that are shorting out the module as suggested earlier by taking off the flywheel housing to get to the module. If I don't see any problems with the wiring, it looks like I need to order the ignition module.

 

[Jags]

I assume you are talking about the electronic magneto ignition module, right?

Yep, dats da dude.

 

[wkpoor]

I think it is important to note (even though it does appear you headed in the right direction here) that checking spark in free air with a plug that only has maybe a .025" gap is not a valid check. It can lead you down the wrong path. To really know you have adequate spark you need to subject the coil to the same level of stress it sees under compression. I illustrated how to do that in my previous post.

 

[wkpoor]

This capacitor and the coil’s primary windings form an oscillating LC circuit. This LC circuit produces a damped, oscillating current which bounces energy between the capacitor’s electric field and the ignition coil’s magnetic field. The oscillating current in the coil’s primary, which produces an oscillating magnetic field in the coil, extends the high voltage pulse at the output of the secondary windings. This high voltage thus continues beyond the time of the initial field collapse pulse. The oscillation continues until the circuit’s energy is consumed.

Dude what planet are you on? It can't be earth. No sense in going any further with this as its not helping the OPs probelm at all.

 

[stejus]

I think it is important to note (even though it does appear you headed in the right direction here) that checking spark in free air with a plug that only has maybe a .025" gap is not a valid check. It can lead you down the wrong path. To really know you have adequate spark you need to subject the coil to the same level of stress it sees under compression. I illustrated how to do that in my previous post.

wepoor - I think I confirmed this by plugging the sparkplug boot into the plug that was installed into the cylinder head. This [lug was the same plug that started the engine, ran for 20 minutes and shut down. After letting the engine cool, I tested the open air plug for spark and then I plugged the boot into the installed plug and the engine started. This tells me after the engine has heated up, the coil seems to be failing. Once the engine cools, the coil is fine again until it heats up.

 

[wkpoor]

I think it is important to note (even though it does appear you headed in the right direction here) that checking spark in free air with a plug that only has maybe a .025" gap is not a valid check. It can lead you down the wrong path. To really know you have adequate spark you need to subject the coil to the same level of stress it sees under compression. I illustrated how to do that in my previous post.

wepoor - I think I confirmed this by plugging the sparkplug boot into the plug that was installed into the cylinder head. This [lug was the same plug that started the engine, ran for 20 minutes and shut down. After letting the engine cool, I tested the open air plug for spark and then I plugged the boot into the installed plug and the engine started. This tells me after the engine has heated up, the coil seems to be failing. Once the engine cools, the coil is fine again until it heats up.

Actually when it comes to solid state ignition with the coil built in (assuming as such) the failure could be in the transistorised points. Either way its a module replacement. Now for the record I'm not sure you understand any free air ignition check should be done with a much larger gap than what a spark plug has. A 3/8"-1/2" gap will simulate .025" under pressure. People do get away with checking spark by pulling a plug and lying it on the engine for ground alot but its only valid for hard failures.

 

[basod]

In case your having trouble finding the manual/pn
Found this site a while back to get some parts for a B&S
http://www.partstree.com/parts/?lc=...eed+1700+RPM/High+Speed+3350&dn=catalogs_1157
Not sure which specific model you have they only display CV12.5 and CH12.5 (you said 12hp)with multiple variations, I'd suspect they all have the same ignition coil/module.
(broken link removed)

 

[MasterMech]

I think it is important to note (even though it does appear you headed in the right direction here) that checking spark in free air with a plug that only has maybe a .025" gap is not a valid check. It can lead you down the wrong path. To really know you have adequate spark you need to subject the coil to the same level of stress it sees under compression. I illustrated how to do that in my previous post.

wepoor - I think I confirmed this by plugging the sparkplug boot into the plug that was installed into the cylinder head. This [lug was the same plug that started the engine, ran for 20 minutes and shut down. After letting the engine cool, I tested the open air plug for spark and then I plugged the boot into the installed plug and the engine started. This tells me after the engine has heated up, the coil seems to be failing. Once the engine cools, the coil is fine again until it heats up.

Which is the exact pattern of symptoms for coil/module failure. Get yourself a module and get it running.

 

[stejus]

In case your having trouble finding the manual/pn
Found this site a while back to get some parts for a B&S
http://www.partstree.com/parts/?lc=...eed+1700+RPM/High+Speed+3350&dn=catalogs_1157
Not sure which specific model you have they only display CV12.5 and CH12.5 (you said 12hp)with multiple variations, I'd suspect they all have the same ignition coil/module.
(broken link removed)

Thanks, I found my model and the the drawings and the part on this link. It's #18. I did happen to find the same part for a lower cost on another site though.

http://www.partstree.com/parts/?lc=...1750+RPM/High+Speed+3400+RPM&dn=catalogs_1289

I also found a video that walks you through it. How sweet is this... about a $150 savings rather than bringing it to the small engine shop.

http://www.youtube.com/watch?v=kAVubYlhAwM

 

[basod]

Glad we could help solve the problem and save some coin

 

[stejus]

Ok, here's the latest. I was able to get the Ignition coil out. I had to disconnect this wire that leads back to a connector with other wires. Look at the wire and notice it has been chewed and the insulation and rubber jacket is missing on some of the wire.

Could this be the root of the problem seeing the bare wire may be hitting metal and shorting out the ignition? I want to say no because it seems to happen when the engine heats up. In any case should I wrap the wire up with electrical tape or get a new wire kit?