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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Tractors Owned: 1948 Farmall Cub (sn 26136), named Rosalie
Location: Cape Breton, Canada

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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IHCFan1950
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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.
If a sharp rap with your hammer doesn't work, you know it's an electrical problem! :lol:

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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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CaperKen
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Tractors Owned: 1948 Farmall Cub (sn 26136), named Rosalie
Location: Cape Breton, Canada

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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