S650g ignition coil questions

[ShelleyJ]

My Satoh S650g hasn't been started in years and it won't start now. It turns over good but not firing up. I am getting very weak spark, you have to look close to see it, and it's yellow/white. I have been trying to test the coil. It's getting battery voltage when key is on. Across the 2 outer terminals measures 2.3 ohms (multimeter set at 200). Center terminal to either outer terminal reads 8.9 ohms (with multimeter set at 20k). So, I'm thinking I'll try a new coil, but am confused what I need. The one on the tractor now says "use only with external resistor" 12v Made in USA and the number 503. I assume this is not the original coil. But I can't see the external resistor anywhere in-line. Should I buy one of the coils that doesn't require external resistor? Could the lack of a resistor with the current coil be causing the starting problem?

 

[Roadworthy]

Lack of a ballast resistor could indeed have damaged the coil. If you have no ballast resistor and no provision for one by all means get a coil which doesn't require one. Just make sure it fits your mounting area.

 

[jaxs]

There isn't a silver bullet answer covering not start situations.
Did you use starting fluid? How many volts coming into coil? Have you checked point gap? Have you cleaned contacts? What is max distance spark will jump? If an engine with less than perfect psi compression sits for years cylinders dry causing low compression. With upright horizonal cylinders 1/2 oz diesel or transmission fluid in each hole followed by a few revolutions with plugs installed followed by cleaning plug tips with solvent helps initial start up. For slanted vee cylinders use straw to spray top of cylinder walls through plug holes with oil.

 

[ShelleyJ]

Sorry this is a total learning experience. I've been reading up on points since I had no idea how they work and that is what I planned to check next. What I can answer is the spark jumping...the gap had to be very small, almost touching, before I got any spark, and it's very weak. This was checking it at the coil, distributor cap, and one of the spark plugs. Also the voltage coming into the coil was 11 something volts, which I'm assuming the battery is slightly down.

Roadworthy, do you know if this model originally came with an external resistor? Maybe it's hidden up inside the dash where it's not obvious? I read one thing about a different brand tractor that had the resistor mounted that way.

 

[jaxs]

Sorry this is a total learning experience. I've been reading up on points since I had no idea how they work and that is what I planned to check next. What I can answer is the spark jumping...the gap had to be very small, almost touching, before I got any spark, and it's very weak. This was checking it at the coil, distributor cap, and one of the spark plugs. Also the voltage coming into the coil was 11 something volts, which I'm assuming the battery is slightly down.

Roadworthy, do you know if this model originally came with an external resistor? Maybe it's hidden up inside the dash where it's not obvious? I read one thing about a different brand tractor that had the resistor mounted that way.

11 "something" volts to coil tells us there is no resistor UNLESS you are keeping it secret that coil has 2 wires connected to incoming side. Charge battery,use a piece of cardboard such as from a cereal box to clean points then see how much spark you have.

 

[Roadworthy]

With eleven volts to the coil when the ignition switch is on you probably don't have a ballast resistor in the circuit. You may have a weak battery or bad contact at the battery. Clean and tighten cables. Don't overlook the frame ground. Battery voltage should be about 12.6. Check the gap on your points, it is important that it be correct for proper spark. Your condenser can be defective and that can affect the spark. Opening and closing the points is what causes the spark. If they're open too long or not long enough the spark is affected. The condenser is supposed to damp the spark at the points to slow or reduce burning and pitting. If it's leaky the points are not "seen" as opening properly. If it's removed from the circuit or open there will be significant sparking at the points which burns them.

 

[ShelleyJ]

Well I killed it completely somehow. I took off the distributor cap and the shaft was turned to where the points were closed. I read on another post here that you can turn the key to start with the cap off to check for position. I did it twice and the position still wasn't right. The next time I turned the key to start I got absolutely nothing. Not even a click from the starter. The gear shift and range lever are both in neutral, just FYI for the safety switch. Still getting battery voltage at the ignition coil + post when key is in run position. (Battery is at 12.1 volts.) I stopped there since I don't know what could have gone wrong or what else to test. Sigh...

 

[ShelleyJ]

Is there supposed to be spark at the points or is that what burns them up? I was getting a pretty big spark.

 

[ShelleyJ]

So after sitting overnight, the tractor healed itself and will turn over again. What on earth could cause it to do that?

 

[jaxs]

Things can't be so bad you can't afford a mechanic. I have to hire professionals to do several things for me and I wouldn't dream of cutting my own hair using instructions from people here.