Engine miss

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Re: Engine miss

Postby Jason_Coffey » Wed Nov 06, 2013 2:22 pm

I just noticed on my coil in small white letters (printed on light gray, and not so easy to see) the coil requires an external resistor. Could this cause a miss? I don't have a resistor connected to the coil. Should I go by the IC14 coil from Napa?
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Re: Engine miss

Postby Eugene » Wed Nov 06, 2013 2:45 pm

Jason_Coffey wrote:I just noticed on my coil in small white letters (printed on light gray, and not so easy to see) the coil requires an external resistor. Could this cause a miss? I don't have a resistor connected to the coil. Should I go by the IC14 coil from Napa?

http://www.pertronix.com/support/manual ... 12vneg.pdf

Cheaper to purchase a Chrysler ballast resister.
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Re: Engine miss

Postby John *.?-!.* cub owner » Wed Nov 06, 2013 6:56 pm

Missing resister would not cause a miss, but would cause coil to fail sooner
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Re: Engine miss

Postby Eugene » Wed Nov 06, 2013 8:36 pm

Go back to my previous post. If your description of the problem(s) is/are accurate.

1. You have a problem with the mechanical advance within the distributor.

2. You have a problem with the Petronix's firing the #3 cylinder multiple times when it should be firing the cylinder once per combustion cycle.
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Re: Engine miss

Postby Jason_Coffey » Thu Nov 07, 2013 10:29 am

I was messing with the timing again last night. I installed the $12 Chinese tach and noticed that my cub is idling around 690 rpms. Per the manual it should be around 475-500. I can't get it to idle that low. If I lower the idle below 610 rpms it will die. Could these two issues be related?

Eugene, I agree the advance in the distributor is not working. I can't really pull it out right now to mess with it. We are moving to our new place next week, so I will have to wait until we get moved. So I will be picking your brain about this in a couple of weeks I'm sure. I am also going to Napa today to get a different coil and some 8mm wires. The cap and rotor were new when I picked up the cub from the PO, but I may buy those too just to rule them out as a problem. I'm starting to think, I might be better off just having the engine rebuilt.
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Re: Engine miss

Postby Eugene » Thu Nov 07, 2013 12:43 pm

Rebuilding the engine won't solve the ignition problem. Previously stated, #3 cylinder 80 psi, other cylinders good. So, I wouldn't overhaul the engine at this time, just operate it for a while to see if things improve.

I also wouldn't purchase and exchange parts hoping that would solve the problem(s).

First thing to fix is the distributor. Then go back to points and condenser ignition. Once tractor is running properly, then install the Pentronix ignition system.
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Re: Engine miss

Postby Bus Driver » Thu Nov 07, 2013 12:52 pm

The Pertronix rules out the possibility of a bad insulating bushing/grommet where the primary wire passes through the body of the distributor.
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Re: Engine miss

Postby Smokeycub » Thu Nov 07, 2013 12:58 pm

Jason_Coffey wrote:I put the light on it and checked all four cylinders. The only thing I noticed was the rate the light flashed on #3 would flash so fast at times it was almost a solid light for 1-2 seconds then it would go back to a normal rate of flash.

I have two thoughts. The air gap for the pickup coil needs to be fairly precise. It sounds like something isn't quite spaced right, like maybe something is shifted so that when #3 is set to fire the air gap is a bit too large. ...and or the distributer shaft has a little slop or wobble in it.
Eugene wrote:Pull the distributor. Check mechanical advance and condition - repair. Then reinstall the points and condenser - see if the condition persists.

I believe Eugene is saying replace the electronics with the points.

If it's not the ignition then it sounds to me like a valve isn't seating well.
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Re: Engine miss

Postby Jason_Coffey » Thu Nov 07, 2013 1:08 pm

I will have to buy points, condenser, and a leaf gauge to swap out the petronix. I don't have the old ones. If I were to record the engine running so you could hear the miss, would that help diagnose the problem?
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Re: Engine miss

Postby Eugene » Thu Nov 07, 2013 1:26 pm

Jason_Coffey wrote:If I were to record the engine running so you could hear the miss, would that help diagnose the problem?
No, an audible recording won't help.

Problem should be plural as in problems. Solve one at a time.

You should have the points and condenser on the shelf, as spares.

Thickness gauge. 4 sheets of regular typing paper will get you to around .019 to .020" for the point gap. Or two thicknesses of manila folder will get you to .019 to .020" Close enough for the Cub's engine.
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Re: Engine miss

Postby newfurrows » Thu Nov 07, 2013 9:23 pm

How old is your gasoline? My '64 ran like that when I got it. Drained the gas tank, put new gas in and it ran perfectly without a miss. Worth a shot.

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Re: Engine miss

Postby Jason_Coffey » Thu Nov 07, 2013 9:44 pm

Swapped out the coil with an IC14 from Napa. I also switched out the plugs again. The miss is gone. The #3 plug was fouled and the other three were a perfect tan color.
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Re: Engine miss

Postby mrdibs » Fri Nov 08, 2013 4:23 pm

You said #3 was at 80. What's the difference between the other 3? When mine was missing, it would periodically backfire through the carb and had no HP. In my case the head was warped. Compression mismatch was about 15 between the best and worst. Only other evidence was a little bit of bubbling from between the head and block near #3. Having the head milled was the last thing I tried, and the only thing that worked. Maybe there's a way to positively test for it.
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Re: Engine miss

Postby Jason_Coffey » Sat Nov 09, 2013 11:58 am

20psi difference between the other three and #3. The compression has come up considerably since I first checked it. I think it just needs to run and free everything back up. I plan to add some seafoam to the oil soon and let it run a while before I drain it.

If there is a way to test for a warped head I would definitely try it.
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Re: Engine miss

Postby Eugene » Sat Nov 09, 2013 2:39 pm

Jason_Coffey wrote:If there is a way to test for a warped head I would definitely try it.
Compression test, dry then wet. I don't think that a warped head is the problem with #3 cylinder. More than likely worn or stuck rings since that cylinder is pumping oil - fouling the spark plug.

Just go ahead with the SeaFoam treatment, work the engine. It may take a while for the rings to free up - maybe never. In the mean time, you will probably continue to foul the spark plug. Next time you have to replace the #3 plug, go with a hotter plug and open the gap up a bit.
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