No spark, what next?

[Jeff244]

I am trying to get an old piece of equipment running. It has a 12hp Kohler engine. It has been sitting for at least 15 years. I installed a new plug and a condenser. I can see a spark at the points, but nothing at the plug. What should I do next? I am told it has a magneto, could that be the problem?


Thanks,
Jeff

 

[bjcsc]

If it was the magneto, you wouldn't have the spark at the points. The magneto generates the electricity that makes the spark and it controls the timing. Just keep going. If the points are gapped right, follow it to the plug wire. Make sure the plug has a good ground when you're trying to check it.

 

[Jeff244]

bjcsc,

Thanks for the response. What do you mean by "Make sure the plug has a good ground when you're trying to check it"? I just stuck a screwdriver in the spark plug wire and held it next to the plug while cranking the engine, did I do it wrong? Sorry, I am not much of a mechanic but I am trying to learn.


Thanks,
Jeff

 

[Jeff244]

One more question.

I am trying to get some info on the web and came across this: " The condenser acts as an electrical shock absorber to prevent arcing between the contact points as they open". Does that mean that there should be no spark there? Because I see a pretty good spark at the points while the engine is turning.

Thanks,
Jeff

 

[Treemonkey1000]

I would wonder about the condition of the plug wire metal contact that fits on the plug. If you are getting spark across the points then that is half the battle. Did you say you were getting spark across a screw driver holding the plug down? If you can hold the metal body of the plug so that it makes contact with the cylinder head. Then crank it. If you see spark across the small gap in the plug then there is some other problem. Like valves are hung open for no compression. You could spray some starting fluid in the plug hole then reseat the plug and crank it. See if it pops. Gas, compression, and a bit of spark and you should be in business for the most part.

 

[zzvyb6]

If there is a spark at the points, the condenser is bad. Moisture probably got into it. The condenser stores the energy from the induction of the flywheel magnetic field into the primary side of the coil as the points close. When points open the condender dumps and the 'large' change in voltage (delta V) creates a VERY large inducted voltage in the coil secondary. Another option would be that the coil is bad (open). A meter would tell you this. It could just be a shorted spark plug, too. Oil soaks into the insulator over time and its not an insulator anymore. I've never been able to unshort a shorted plug once it goes bad.

All this is under the presumption that the flywheel has not spun by the keyway so that it got out of time. A backfire can cause this. If so, the points and the mag alignment are now seriously out of phase. You would notice that the key was split into 2 pieces.

Points & condenser from Home Depot or TSC would be my first play. Clean the wiring up so there is no possibility of short circuits from oil permeation.

 

[alchemysa]

bjcsc,

Thanks for the response. What do you mean by "Make sure the plug has a good ground when you're trying to check it"? I just stuck a screwdriver in the spark plug wire and held it next to the plug while cranking the engine, did I do it wrong? Sorry, I am not much of a mechanic but I am trying to learn. Thanks,
Jeff

He means unscrew the spark plug then somehow clamp it securely to some metal part of the engine. Re-attach the spark plug wire and crank the engine over. Its best done in the shade because the spark can sometimes be hard to see.

 

[bjcsc]

Exactly. Unscrew the plug, make sure the end of it is clean, put the plug wire on the plug. Then hold the end against a good ground, like a cleaned part of the block or head. If it's a pull start, it's easiest to have someone else pull it while you look. The spark can be hard to see and yes shade or darkness helps. Another thing you can check is the gap on the plug. Sometimes they are sold in spec, but most of the time (IME) they are out. While you have the plug out, you can turn the engine over and sniff the air coming out of the plug hole. Should smell like gas. Once you get a spark, turn it over a bit before putting the plug back it (in case it's flooded - helps dry it out).

Most small engine problems, esp. from sitting, come from carburetors. You may want to cut to the chase and just rebuild the carb from the get go.

Find your spark - you can do it!

PS. When you hold the plug, hold the insulated part of the plug wire...

 

[Soundguy]

A condensor in a kettering ignition system is a SWITCH DEBOUNCER.. check it out on the internet... primry current charges the field in the coil when points are closed.. points open, field colapses, large voltage is induced on the secondary... condensor helps prevent points from arcing and burning...

soundguy

If there is a spark at the points, the condenser is bad. Moisture probably got into it. The condenser stores the energy from the induction of the flywheel magnetic field into the primary side of the coil as the points close. When points open the condender dumps and the 'large' change in voltage (delta V) creates a VERY large inducted voltage in the coil secondary. Another option would be that the coil is bad (open). A meter would tell you this. It could just be a shorted spark plug, too. Oil soaks into the insulator over time and its not an insulator anymore. I've never been able to unshort a shorted plug once it goes bad.

All this is under the presumption that the flywheel has not spun by the keyway so that it got out of time. A backfire can cause this. If so, the points and the mag alignment are now seriously out of phase. You would notice that the key was split into 2 pieces.

Points & condenser from Home Depot or TSC would be my first play. Clean the wiring up so there is no possibility of short circuits from oil permeation.

 

[Jeff244]

Thanks for the responses,

OK, I filed the rust off one of the head bolts, put a wire in the end of the spark plug wire and held it next to the bolt. I got a small spark! It was small and seemed to be intermittent but that may be because its in a fairly bright area. I stuck the spark plug in the spark plug wire and held it next to the bolt and got a spark, but it seemed weaker and much less frequent than just using a piece of wire. I checked the compression while the plug was out, it's around 120 psi. I also smelled gas blowing out of the hole. But I cannot get the engine to catch at all. I sprayed starting fluid in the hole before putting the plug back in and sprayed it in the air cleaner. What now?

 

[Jeff244]

I was going to change the points, but I decided to try some sandpaper on the old ones. And it worked!!! The engine is running. This is just the beginning, but now I can start checking the other systems to see if they work. Thanks for all the help.



Jeff

 

[Treemonkey1000]

I would try a new plug if you haven't already. Then if you can get to the points make sure they don't look to burned and pitted. You can clean the point contacts with a very fine sandpaper. The gap on the points might be tweaked a little into a better gap. If you put starting fluid in it and it didn't give you a warm fuzzy feeling about trying to start then the spark maybe too weak. Rust and crud may have collected where the coil pick up is. You mentioned smelling gas coming out of the plug hole which is good. By chance is that fresh gas in the tank? Old gas will not burn too well and cause you headaches.. (voice of experience). 120 PSI of compression doesn't sound too far off the mark I think.
oops I hit the send for this message and then saw that you got it running.. YEAH

 

[Soundguy]

Now that you have sanded the points.. try to make them last by pulling a piece of brown paper bag.. or white typing paper thru them to clean any residual oil or grit of fthem that will cause them to pit and burn further..

soundguy

 

[Jeff244]

Treemonkey1000, thanks, you were right about the points. It seems that everything is working on the machine (an old asphalt roller) I drove it up an down the driveway for about 10 minutes. My wife was laughing at me but I am used to that.


Soundguy, good info, that makes a lot of sense.



Jeff

 

[Treemonkey1000]

Hey park your wifes fanny up there and let her drive it.. She might have a bit of fun then..
Soundguy is right about polishing them points up a bit.

 

[Jeff244]

Treemonkey1000, she has actually spent a lot of time on that roller. Right after we got married, I made a comment about women and truck driving. A month later she had her license and drove a truck for me(I had a small paving company). A few months later she tired operating the roller. She was the roller-person for about a year and a half until she went and got herself pregnant . She was one of the best drivers and operators I ever had.


Jeff