Lost spark again after changing points

[marshall]

Points gap the same to cam on both sides. I've reinstalled being very careful of ordering the elements on the post so that everything looks good. I got fan rotated to the mark just after plug 1 generates air pressure and installed rotor pointing to top. Still no start. Am assuming there's still no spark at plugs.

Is the next move to buy a new coil and hope this is the failed part? I'm noticing no reading on my ammeter. Battery is definitely charged.

BTW. Is it true that operating at load can blow the coil???

[Glen]

Hi,
Thanks for writing about what you checked.

They usually say on here to replace the condenser first if there is no spark, since they cost less than a new coil. Either one can quit working.
NAPA sells points and condenser for the Cub separately, the last time I checked there.

I've never seen any problem with the Cubs I have seen, caused by working the engine for long periods of time, or lugging the engine down from high speed to stopped.
It hasn't caused any ignition system problem.
Just start the engine again, it should work normally.

[Rick Spivey]

Your points sound like they are operating just fine. If you have spark at the points, but not at the spark plug, then there is an issue in one of the following:
secondary winding of the coil
coil to distributor cap wire
distributor cap
rotor
spark plug wires
plugs

It is almost impossible to tell you which is most likely, so start eliminating the easy ones first. If your plugs are fairly new, I would eliminate those unless they are fouled out. If your wires and cap are fairly new, just check the cap for a crack; if not new check the inside and outside contacts for corrosion. Rotor should be easy to check. If all that seems good, then maybe the coil is bad.

There is only one test that I use for the coil, and it only tells you if there is a major flaw in the windings. You can use an ohm meter to check from the small primary wire to the tab that is under the hold down screw on the coil. That is the two ends of your primary winding so there should be continuity. Then check actual ohm reading from each of those ends of the primary winding to the "nub" on the coil that touches the coil cover; you should get a reading of 9500-11000 ohms. If open (0), there is an issue, and if the reading is anything else, likely a bad coil. This is not an exhaustive test but I find it catches most bad coils.

[marshall]

My son who fiddles with electronics tells me that if the condenser is a capacitor, then I should be able to connect it directly to the battery which will put a 12 v charge into it. I should then be able to use my volt meter on the condenser to see if it gives a 12 volt reading.

Would this be a way I could check to see if the condenser is shot?

[Eugene]

My son who fiddles with electronics tells me that if the condenser is a capacitor, then I should be able to connect it directly to the battery which will put a 12 v charge into it. I should then be able to use my volt meter on the condenser to see if it gives a 12 volt reading. Would this be a way I could check to see if the condenser is shot?

No on the 12 volt reading.
A condenser is a capacitor. The difference in terminology is where the capacitor is utilized.
Many multi-meters have the ability to accurately test capacitiors. Check your multi-meter's owners manual.
Less than accurate test. Multimeter on high Ohms setting. Connect leads to capacitors terminals. Ohms reading should slowly rise, then fall back to zero, then rise.

[marshall]

Using a multimeter I tested the ignition system and found that my condensor is working. I then did some troubleshooting on the remaining system. Spark plug wires have continuity, distrib cap in good shape with polished contacts - no cracks, plugs clean and gapped correctly (but no spark when cranking). Using the multimeter while cranking we found lots of numbers (noise) when testing the output of the coil so assumed there is voltage coming out (of some sort). After connecting coil cable we find same noise at the end of the cable where it would attach to distrib cap. After attaching coil cable to distrib cap and to magneto with multimeter on a plug output terminal on distrib cap, though, we don't see this same noise so the hypothesis is that the rotor isn't distributing the noise voltage to the plugs. I replaced J4 rotor but it didn't solve the problem. I'm wondering if maybe the rotor didn't mesh at the same location as the old one which would leave the timing off. If I didn't mesh the rotor correctly in conjunction with the timing of the engine, is the procedure to just get crank it to TDC at plug 1 and then move the rotor up to the top at plug 1? If this doesn't fix the problem, I'm kind of stumped because points have been replaced and I don't see ways to accurately isolate parts to determine culprits and just buying new parts and installing them is expensive. I guess buying a new coil and hoping is the final move.

[Waif]

Insulating piece points rest on intact?
Could be shorting out or partially grounded robbing current. Only guessing that because you had juice before connecting to distributor.

A known good coil is the only way for me to know if it's coil issues. But , that's just me too.

[Glen]

Hi,
The rotor and it's drive gear have timing marks on them that need aligning when you put them together.
You didn't say if you aligned them.
Since you replaced the rotor, check it drive gear's teeth, if they are worn, the drive gear, or pinion it is called should be replaced.
Below is a listing at TM Tractor for it, you can look at the pics.

http://www.tmtractor.com/new/el/615fp.htm

Below is a pic of the timing marks.
The old grease should be cleaned out, and new grease put on the gears, if it hasn't been done lately.

[Glen]

Hi,
To check the spark the magneto puts out, plug an ignition wire in the coil post, and hold it by the insulation of the wire, with the metal end about 1/4" from the metal of the engine block, if the magneto is on the engine, when checking the spark.
Be sure the transmission is in neutral, turn the ignition switch to on, and run the starter.
The battery should be fully charged before doing the test.
The spark should jump the 1/4" gap, and be blue or white. A yellow spark is weak, and needs improving.
The engine may not run with a yellow spark.

[marshall]

Glen. This sounds like a way I could check to see if the coil is good.
Also, thanks for the pointer about the timing marks on the rotor. I'll clean out the grease and look to make sure they're aligned. I'd be surprised if I got lucky and put it on correctly without seeing them.

I guess if I buy a new coil I may as well throw in new spark plug wires and a distributor cap and then I will have replaced everything. I've got Autolite 3116 plugs in there. They seem to have been fine. Are there others that people have found to be markedly better?

[Bob McCarty]

Make sure the new plug wires are solid core and not carbon core.

[69ranger]

Lots of good suggestions here, and I probably cant add much, but I feel your pain. I fought this one summer, and I was about to decide that I was too dumb to work on a tractor.

If I were you, I would remove the mag from the tractor. They are much easier to trouble shoot on the bench.

I check spark at the coil first and then move to the individual wires. As was mentioned rotor timing is critical.

Yes. make sure the spark can go to ground, and not discharge into the air. Discharging into the air is tough on coils. Your coil could be bad, as things are not as good as the used to be. However I would investigate a few other things before I gave up.

It may be a dumb suggestion, but wires, even copper core break down over time.
I fought hard starting, and poor performance a few summers ago. Knew it was ignition related, and had changed and reset points, replaced the condenser, cap, and even changed the coil. Things got a little better, but it started hard, and if I killed it under a load, it would usually not start.
Got to checking one night, with a self powered timing light, and I had good hot spark off the Coil, but a really weak at all the wires.
Changed the wires and solved the problem. After I finished putting the new wires on, it started like normal again.
So I cut into some of the wires, and found that corrosion, had eaten the copper up. The copper core was green and fell apart when you touched it.

[marshall]

It was indeed the rotor being on wrong. I got it lined up like in your picture and did a quick test of the coil wire and saw sparks, then tested a plug, saw sparks, and put it all back together and its running!

Thanks to all who guided me through this. I avoided buying another coil and only replaced points, condenser, and rotor so the outlay of money wasn't too bad. Now I'm back to troubleshooting the initial problem which was that my PTO pulley fell off and now I'm not getting PTO drive which I'm going to post in a new thread. Maybe by August I'll be able to cut the field that I was cutting in mid June when the failure knocked me out.

[Glen]

Hi,
Good that you got the Cub to run.