My Cub's Fire Has Gone Out!

[jpate831]

Happy Saturday, Everyone!

I was moving mulch with my '47 Cub and IH 1000 loader a couple weeks ago. It was running great as always. I'd been working with it for about an hour or so with no issues, when suddenly it shut off like I'd hit the ignition button. I checked and there was plenty fuel, so I tried to start it again. It turned over a few times, but the 6V battery was weak and it soon stopped turning over. I turned it with the crank several times, but it never fired.

I had the 6V battery tested, and it was bad, so I replaced it. When I engage the starter, it turns over great, but it never fires.

I don't seem to be getting much if any spark to the plugs. I took one out and cranked while I looked for a spark, but I did not see any spark.

Most of the people I talked to said it was either the Coil or the Points and Condenser, so I replaced each of them one at a time, but it didn't change anything. I've been fiddling with it for the last 2 weeks. Here's what I've done so far.

Replaced 6V Battery
Replaced 6V Coil
Replaced Points and Condenser
Replaced Distributor Rotor Button
Replaced Distributor Cap
Replaced Spark Plugs
Replaced Spark Plug Wires
Replaced Ignition Switch

I tried connecting a light bulb to the Coil output wire, but I can't seem to get the light to come on. If I actually hold the wire coming out of the coil I can feel a bit of current coming through it as the engine turns over, but it seems quite weak. It my experience, holding the lead like that would be enough to put you on the ground if a distributor was firing correctly.

My next thought is replacing the Distributor, but I don't want to do that unless it makes sense to do so. But that's about the only component of the ignition system that I haven't already replaced!

Any thoughts?

Thanks in advance.

[SamsFarm]

I'd probably try a jumper wire from the battery to the coil.

Well actually, I would probably grab my meter and check to see if I was getting proper voltage to the coil first.

Everyone is saying new points have a coating on the contacts that needs cleaned off!

[Glen]

Hi,
I agree with the above.
Test to see if battery voltage is getting to the coil. You could test at the battery, and see if the battery has a full 6 volts.
It's unlikely replacing the distributor will do any good, if it's in good condition.
There is an insulation in the side of the distributor where the small wire is connected to, the end of the point spring is there on the inside. The insulation can crack and cause a short there.
TM Tractor has a new insulation if you need it.

[jpate831]

Should the points spring touch the condenser wire connector?

[Glen]

The end of the condenser wire goes on the post, along with the end of the point spring, if that is what you meant. The nut holds them both on the post. Tighten the nut gently, the insulation in the side of the distributor can crack.
A point file removes the coating that they say on here is on some new points. Wipe the points with a clean rag after using a point file.

[tst]

did you set the point gap to .020 ?

[jpate831]

Yes, I did set the point gap to .020, and I filed the points somewhat...maybe not enough, I guess.

Let me see if I understand this system. The coil has a wire coming from the ignition switch to it's negative post. The coil's positive post has a wire going to the distributor terminal, which is insulated from the distributor itself. Inside the distributor, on the same terminal, the points spring and the condenser wire are connected. The other (non-spring) side of the points is grounded to the distributor, and the tractor. So when the points make contact, they complete the circuit to the coil, which also charges the condenser. Then when the points open, the condenser releases its charge back to the coil, producing a spark. Do I have that correct?

So if the terminal insulation is broken, it's essentially grounding out the condenser and not allowing a healthy spark through the coil. Maybe that's my problem? And if the points aren't making good contact, then the condenser isn't getting charged sufficiently to produce the spark the tractor needs.

Am I on the right track?

[staninlowerAL]

I do understand that you have replaced the 6v coil but I suggest that you try a known good coil to determine if your new one is working correctly. I had a similar problem when my engine would not start even though the points arched every time the distributor rotated. In my situation the problem was a failure of the high voltage side of the coil (internally). When I replaced it with a known good coil, it resolved my problem. You can observe the points action by removing the dist cap and internal cover, then rotate the engine a watch for the points to arc when they open and close. Good Luck! Stan

[inairam]

A few years ago I started using NAPA for all my ignition parts. With the ignition parts from the tractor sites I have had condensers be DOA (even IH/case-labeled ones) and coils have a short life. The NAPA points are noticeably different at the spring and contacts.

As others have said the first thing is to check for voltage at the coil before you start replacing parts.

[Rick Spivey]

Yes, I did set the point gap to .020, and I filed the points somewhat...maybe not enough, I guess.

Let me see if I understand this system. The coil has a wire coming from the ignition switch to it's negative post. The coil's positive post has a wire going to the distributor terminal, which is insulated from the distributor itself. Inside the distributor, on the same terminal, the points spring and the condenser wire are connected. The other (non-spring) side of the points is grounded to the distributor, and the tractor. So when the points make contact, they complete the circuit to the coil, which also charges the condenser. Then when the points open, the condenser releases its charge back to the coil, producing a spark. Do I have that correct?

So if the terminal insulation is broken, it's essentially grounding out the condenser and not allowing a healthy spark through the coil. Maybe that's my problem? And if the points aren't making good contact, then the condenser isn't getting charged sufficiently to produce the spark the tractor needs.

Am I on the right track?

You are correct in most everything stated above. The main function of the condenser is to "buffer" the amperage going through the points when they open, so they won't burn as fast. I've heard the condenser also discharges back into the coil when the points open. helping the spark. I was never taught that, but I suppose it can be true. However, the bulk of the spark comes from the coil, which has a primary and a secondary winding internally. The primary winding is the smaller wire going to the points. The secondary winding is the larger wire going to the plugs. The two windings are separated in the coil. When you create current flow in the primary winding, you inductively create a current flow in the secondary winding. Because the secondary winding is much larger, your current is higher in voltage, but necessarily lower in amperage. That is why a coil or spark plug wire will zing your hand, but not kill you. I may be somewhat mistaken in my memory, but when I was in shop class I think we were told older points-based systems were capable of something between 20,000 and 40,000 volts, but at very low amperage. Today's HEI ignition systems are likely more like 60,000 - 80,000.

It does sound like you should insure that the terminal insulation is working, and that none of the terminal ends is touching the distributor housing. The condenser wire in particular often likes to touch the distributor housing on its back end if you don't pay attention.

[SONNY]

got a 340 just did the very same thing yesterday!! LOL!! still messin with it out in the middle of the field and so far no go yet! sumpin gotta be shorting out! got juice to the resistor block and coil down thru the points but nuttin to the plugs! Gotta go truckin today so cant work on it til tomorrow!

[jpate831]

Mystery Solved!

I had 2 issues:
1. The distributor terminal was shorted out to the housing. I was getting continuity to the terminal even when the points were open, even when the condenser wasn't connected. Apparently I had the insulator installed with the tab to the bottom? I rotated it 180 degrees, and the continuity stopped. If I have any more issues with that, I think I'll replace the insulator.

2. The new Condenser was apparently bad. I was getting continuity from the barrel to the end of the wire, with it lying on a wooden workbench. I tested the old Condenser, and it had no continuity, so I put the old one back into the distributor. I hit the starter, and it turned over the customary half revolution and started right up!!

Thank you all for your help and suggestions. My Cub's fire has returned!

[Glen]

Good that you got the Cub to run.
Below is a listing at TM Tractor for a new insulator for the Battery Ignition unit, or magneto. You can look at the pics.

http://www.tmtractor.com/new/el/957fp.htm