More testing on Farmall Super C electrical system

[JohnV2000]

Hello,

I tried to follow the tests outlined in replies to my previous post.

I will try my best to summarize what I found.

First, the resistor on top of the distributor is definitely getting voltage from the battery/ignition switch. Also, there is a notable (albeit small) voltage drop across the resistor, which I have heard means the resistor is doing its job.

Then, I used my multimeter to check resistance in the coil. Per the posted instructions, I tested the coils primary winding to be about 1.7 ohms of resistance.

The secondary winding in the coil (the one with the high voltage output to the distributor) tested at about 8500 ohms. From what I read, both of these are good figures.

Next, I tried the test where I put the test light on the distributors small side input, the small wire that comes from the coil and attaches to the side of the distributor. Based on the instructions from a previous post, my test light should flicker when I crank the engine.

However, I ran into a problem doing this test. I am not sure how to slowly crank my engine over. I used the starter to crank the engine, but the test light did not flicker, it only got dimmer when I used the starter. However, I think the starter was cranking the engine too fast for me to even see a flicker with the test light. I do not have a hand crank, so I am not sure how to more slowly crank the engine.

I am also not sure what to test next. The weird thing to me is, the coils secondary winding shows proper resistance (8500 ohms) but yet the high voltage output of the coil will not create a spark when held 1/8 inch from the block.

Any help is greatly appreciated,

John

 

[teddy52food]

Did you clean & gap the points yet?

 

[Steve@Advance]

You would have seen the light flash off and on cranking it with the starter.

Open the distributor, turn on the ignition with the light in place. It should be illuminated.

Short across the points with the blade of a screwdriver. The light should go off.

If it does, the points are corroded or burned or out of adjustment.

Try cleaning and check the gap.

 

[JohnV2000]

Well, I am pretty sure I just discovered the problem.

I really had no idea what to look for in the distributor when it comes to points and gaps, so I watched a YouTube video about distributors and replacing the points, and I think I found the problem.

The metal strip, not sure of the name, that is part of the rotor or points assembly is broken. At first, I thought it was supposed to be two separate things, but I now realize it s broken. When spinning the fan blades, I can see that the points NEVER close because the broken metal strip has the gap way too far.

I apologize if I did not listen to everything everyone said, I was just trying to learn and do my best. I will order the replacement part and hope it works.

Here is a picture of what I think is wrong, the silver flat metal strip is what I think is broken and is the problem:

 

[wore out]

John

"The weird thing to me is, the coils secondary winding shows proper resistance (8500 ohms) but yet the high voltage output of the coil will not create a spark when held 1/8 inch from the block."

John, I'm NOT saying your coil is "bad", it well may not be, but an Ohms test of a coil can only prove it "bad", if a winding tests "open" or way out of "spec.".

On the other hand, an Ohm reading within "specs." does NOT prove it's good/will throw a HOT spark.

Even a single short between windings will weaken the output and dissipate the potential spark energy as heat, yet not affect the Ohms reading noticeably.

To test a coil with reasonable accuracy, a special "ignition coil tester" is needed.

That instrument "rings" the coil with a pulse of electricity and measures how long the coil "rings" as the pulse decays and shows the results on a "good/bad" meter.

Even a good coil tester won't necessarily "catch" a bad coil that shorts when it warms up.

Below is an oscilloscope trace of PART of an ignition spark waveform. The vertical line is the END of a spark event, and the "squiggly lines" following it are an example of "ringing" in the coil.

They will be reduced in intensity and duration, or not present at all in the waveform of a coil with one or more windings shorted.

 

[Rich'sToys]

Yep, John, I think you got it! A new set of points should do it. Make sure they're gapped properly when you install them. Some also suggest running a piece of cardboard between them to clean off any film that may be on them.

Good luck! Glad it was something simple! It often is!

 

[Janicholson]

Yup that was it. Be careful with that pass through terminal where the remainder of the points spring is bolted on. Don't
take it all the way out, in fact just remove the nut from the inside with an ignition wrench (very small %/16 I think). The gap is .020", with the points rubbing block on the high point of the cam. Put a tiny dab of grease on the run=bbing block to keep it from wearing rapidly (about the size of a paper match head. Jim

 

[Rich'sToys]

Ditto on what Jim said. In fact, you shouldn't even have to take that nut all the way off--just loosen it. The end of that spring is slotted and will just slip into place.
Good luck!

 

[John T]

CONGRATULATIONS, Many of us, yours truly included, kept telling you CHECK THE POINTS as that's more often the problem then the coil. Thats
why I (as well as other fine gents) kept telling you to check voltage with points closed versus points open. If they never closed good n
tight your test lamp on the dist terminal WOULD STAY ON ALL THE TIME ...........

YOU DID GOOD !!!!!!!!!!!! I think you learned something yayyyyyyyyyy

Even though I didn't suspect the coil so much, its good to hear you learned and took good resistance checks of the LV primary and HV
Secondary which looked fine. Remember me warning you earlier that although it might pass the low energy low voltage ohm meter tests IT
COULD STILL BE BAD AND EXHIBIT HV BREAKDOWN ONCE WARM AND UNDER ACTUAL OPERATING CONDITIONS.

Thanks so much for the feedback and again you did good

John T

 

[John T]

John, regarding your statement "Also, there is a notable (albeit small) voltage drop across the resistor, which I have heard means the
resistor is doing its job."

FYI had the points been good and fully closing as normal allowing full current flow through the ballast and coil then closed points the V =
I x R Voltage Drop across the ballast would then have been in the 5 to 7 volt range versus the small drop you measured.

John T

 

[Mark-Ia]

Might not hurt to spray the inside of that dist. with electrical contact cleaner to clean it up.

 

[JohnV2000]

Thank you everyone for the kind words and replies.

I just ordered the replacement parts, so I will install them as soon as they come next week.

I will also clean the inside of the distributor like you said, Mark.

 

[Jim.ME]

Do Not throw your old condenser away. It was working. Some failures of new condensers have been reported so it won't hurt to keep the old one as a spare.

 

[gab]

That's it, I've seen that several times on cars. Take an air hose and blow some of the crap out of the dist.

 

[Russ from MN]

The points are the only mechanical part of an ignition system, that's why you should look there first. Electrical and electronics not so much.

 

[JohnV2000]

Thanks for the tips. I will save the old condenser and make sure to use my air compressor to gently blow out the debris from inside the distributor.

 

[timcasbolt]

Hopefully the new contact set will come with a small capsule of grease for the rubbing block. That little bit of grease is far more important than many people realize.