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no ignition but spark OK, gas OK

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CaperKen
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no ignition but spark OK, gas OK

Postby CaperKen » Sat Sep 15, 2018 3:09 pm

Hi

Sorry if this is a dumb question or answered before, but I could not find an answer.

1. My '48 Cub is 12 volt with coil.

2. It was running smoothly and strongly and starting without hesitation and then stopped running altogether (no ignition). It cranks great but no hint of ignition.

3. Battery is good, starter turns over the engine quickly.

4. I just replaced the coil, coil-to-distributor wires, points, condenser, distributor cap, alternator, plug wires and plugs. The wires are 1, 3, 4, 2.

5. I removed and cleaned the carb and replaced parts -- all internals looked quite fine.

6. I checked the spark with a MacTools external spark tester -- blue/white spark.

7. I removed a spark plug and dripped a small amount of gas into the cylinder but no ignition whatsoever -- none.

8. I removed the air intake hose and sprayed ether starting fluid into the carb but no ignition whatsoever -- none.

I have a Pertronix electronic ignition but have not installed it yet since I should have ignition.

I have not done a compression test, but the tractor was working great prior to refusing to ignite.

Other than installing the Pertronix and checking compression, what else can I do?

Most everyone says if you have spark and gas you must get ignition.

I must be overlooking something really simple. Please, what could that be?

Thanks,
Ken

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ricky racer
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Re: no ignition but spark OK, gas OK

Postby ricky racer » Sat Sep 15, 2018 3:43 pm

You've got to have compression as well. Check compression to see if possibility you have a valve stuck open.
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Re: no ignition but spark OK, gas OK

Postby Bob McCarty » Sat Sep 15, 2018 4:44 pm

Where did you check the spark? Sometimes new points have a protective coating/glaze that can be removed by running a strip of brown paper between them. Double check the wiring order.
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Re: no ignition but spark OK, gas OK

Postby tst » Sat Sep 15, 2018 5:14 pm

with the electronic ignition you need to use suppression wires or it can fry the module

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CaperKen
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Re: no ignition but spark OK, gas OK

Postby CaperKen » Sat Sep 15, 2018 5:31 pm

Spark was checked with a MacTools tester. An alligator clamp attaches one end of the wire to the spark plug while the other end has a metal rod that is inserted into the boot at the end of the spark plug wire.. In between is a simple screw device that has an adjustable gap. Turn over the engine and observe whether a spark crosses the gap. I got a good spark. I also tested by removing the plug and grounding against the block and cranking the engine. Again, a good blue white pulsing spark.

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Re: no ignition but spark OK, gas OK

Postby Rick Spivey » Sat Sep 15, 2018 7:32 pm

Depending on what was replaced and what a previous owner might have done, you could still have a timing issue. Double check that at TDC your rotor is pointing to the tower with the #1 plug wire on it.
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Re: no ignition but spark OK, gas OK

Postby Waif » Sat Sep 15, 2018 8:20 pm

No mention of an ignition switch. Or the stock coil grounding kill/run switch. (Assuming 12v was not stock in 48 ,or to my faint knowledge ,a distributor vs a magneto).
Either a separate toggle switch ,or key switch ,or if a stock type switch but with an additional connector....

Anyways ,did you check whatever it has for a switch?
You shouldn't have spark with a bad switch ,but .....

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Re: no ignition but spark OK, gas OK

Postby IHCFan1950 » Sat Sep 15, 2018 9:54 pm

Don't rule timing out of the equation just yet. You may want to check that as well.
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Re: no ignition but spark OK, gas OK

Postby Hnewman144 » Sat Sep 15, 2018 10:23 pm

I had the same exact problem with a cub I bought last week, I had spark, fuel, air, and compression. These guys on here finally pounded it into my head to check timing. So I did, and it was off. I set the timing and she came right to life.

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Re: no ignition but spark OK, gas OK

Postby CaperKen » Sun Sep 16, 2018 11:41 am

Thanks. I've been trying to follow the directions and have hand-cranked the engine to where I feel air pressure on my finger on the #1 plug hole.

I then turned the crank clockwise until the timing slot on the wheel and the timing point on the block matched.

At that point, I checked to see where the rotor pointed and it was NOT in the 2 o'clock position pointing at the #1 spark plug post in the distributor cap.

So, here's my problem. While my Cub is 12 volt with coil, it still has the magneto mounted. The directions I've found seem to all refer to the distributor that replaced the magneto completely in many conversions.

With my setup, how to I rotate the rotor in the 'distributor' cap to point to the #1 spark plug post?

The Blue Ribbon Service Form GSS-1012 seems to explain the procedure under Magneto Ignition on page 5. Is that what I follow even though my Cub is 12 volt with coil? This is a bit confusing for a non-pro.

I'm very grateful for any help.

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Re: no ignition but spark OK, gas OK

Postby butchs38 » Sun Sep 16, 2018 1:34 pm

Check and see where the wire runs to from the post the rotor lines up with. If its not #1 just move the #1 wire to that post then move in order 3,4,2 so your wires would be in this order 1 3 4 2 in a clockwise rotation. Just remember that they are not in the factory position. If it starts you can always move the distributor later running it this way will not damage anything.

,

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CaperKen
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Re: no ignition but spark OK, gas OK

Postby CaperKen » Thu Sep 20, 2018 5:16 pm

I've now static timed my Cub using the Wisconsin Cub Man's YouTube video.

While my Cub is 12v with external coil and magneto, I think that's the right way to go.

Unfortunately, my Cub still won't start. I sprayed some ether into the carb and got two brief burps, but that's it. I still have to check compression but I need to get an adapter for my compression tester for the larger plug hole.

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Re: no ignition but spark OK, gas OK

Postby staninlowerAL » Thu Sep 20, 2018 7:39 pm

CaperKen wrote:....The Blue Ribbon Service Form GSS-1012 seems to explain the procedure under Magneto Ignition on page 5. Is that what I follow even though my Cub is 12 volt with coil? This is a bit confusing for a non-pro. I'm very grateful for any help.

Short answer, yes. The difference with the internal mag coil and a 12v external coil is just the source of the electricity. Mag coil makes its own, external coil comes from the battery.
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Re: no ignition but spark OK, gas OK

Postby Rick Spivey » Fri Sep 21, 2018 5:29 am

Just to repeat some basics. The magneto has a pinion gear that drives the rotor. The pinion gear has a flat in the inside of it's shaft that fits over the armature of the magneto. Be sure that is on correctly. Also, there are casting marks to get the pinion and rotor lined up, they also MUST be correct. Once all that is done, then you can normally only be off by 180 degrees due to placing the magneto drive lugs into the governor slots at 180 off. The governor slots should be at approximately 2:00 and 8:00 positions when viewed from driver perspective. For a magneto to work correctly, even with external coil, all of that has to be "timed" correctly. If any of that is off, you can search or inquire here for further instructions. When using a magneto with external coil, the post that normally connects the kill switch becomes your hot post, delivering the primary voltage to the points. Be sure it is not grounded out on the magneto casing, and that the kill switch has been removed from that post.Your external coil would, instead, be switched upstream of the coil, likely from an ignition switch of some kind. Popping but failing to start usually indicates timing is off, and often by 180 degrees due to faulty insertion of the magneto.
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Re: no ignition but spark OK, gas OK

Postby jim turner » Fri Sep 21, 2018 9:02 am

Spark, fuel at the right time is the key.
Jim Turner


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