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Old 05-23-2012, 02:30 PM   #1
louieglen
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Default #2 missing

I'm having a problem with #2 cylinder missing. It has 68#compression, a new plug, fire going to the plug but still continues to miss. I also installed a new distributor body, the car continues to miss. Any thought's. Thanks in advance.
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Old 05-23-2012, 03:08 PM   #2
mach0415
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Default Re: #2 missing

Have you verified that the valves are opening? Could have a flat lobe on the cam. You will get compression, but no fuel/air mixture if the intake valve is not opening
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Old 05-23-2012, 03:27 PM   #3
ctlikon0712
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Default Re: #2 missing

Have you verified that the plug is sparking? You can have spark to it and the gap be closed or it shorted some other way and not get fire.
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Old 05-23-2012, 05:05 PM   #4
louieglen
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Default Re: #2 missing

Yes the intake valve is opening, and I have put in a new plug with the right gap. Thanks
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Old 05-23-2012, 06:01 PM   #5
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Default Re: #2 missing

When this happened to me (#4 cyl). Same symptoms: Compression tested good, new dist body, new rotor, swapped plugs, etc, etc. Fire to the plug, but no fire in the cyl. It turned out to be a broken vlave stem.
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Old 05-23-2012, 08:47 PM   #6
mach0415
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Default Re: #2 missing

My 2 cents here, but there are base engine issues to look at here. You have established that #1 it is getting spark, #2 it is probably getting fuel and air, and #3 it is getting some sort of compression. To the average tech, he would say that the cylinder should be firing. He should also ask a few more questions and reassess.

Question #1 Was there anything unique that happened, leading up to this? (i.e. Is it a regular driver? or Was the engine sitting for a period of time? - I am having visions of corn and wheat berries, nesting material, etc. blocking the intake port because of critters making #2 intake port/area home sweet home, as found in dad's '29. I know 2 and 3 share the same intake runner, but 2 and 3 split in the block.)

Question #2 Is it a dead miss? I would recommend hooking her up to a vacuum gauge and see what it says. A vac gauge will tell a lot. http://www.fordgarage.com/pages/vacuumtune.htm

Question #3 depends on the answer to Question#2, but How did you conduct the compression test? Intermittent compression will still show up at 68 psi even if it produced that on only 1 good compression-producing stroke, because the schrader valve on the tester would not show an intermittent absence of compression, as it acts like a check valve on the tester.

If there is a result to Question #3, you could do a running compression test on that one cylinder to observe if it is intermittently hanging a valve open on a down stroke, due to a weak/broken spring. If its an exhaust valve hanging, the ole paper cup on the exhaust pipe trick will show it also. The cup will be sucked back to the pipe if the exhaust valve inadvertently opens on a power or intake stroke (sucked open). I have done this many times with great diagnostic success.

This happened on a MoPAR flat head six of mine. A weak valve spring was causing an intermittent loss of compression and a subsequent miss on #1. The tester did not show it for the same reason as above. A cylinder leak down test also did not point to it. Valve springs in these things are pretty low tension as it is. It wouldn't take much more weakness to make it leak.

Hope this helps. These mysteries intrigue me. What can I say? I am a nerd.
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Last edited by mach0415; 05-23-2012 at 09:10 PM.
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Old 05-23-2012, 09:03 PM   #7
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Default Re: #2 missing

Thanks; Some of the test's I have done, the other's I will do tomorrow, Again Thanks to all of you.
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Old 05-23-2012, 09:04 PM   #8
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Default Re: #2 missing

Perhaps a silly question: what instrument or method did you use to determine that #2 wasn't firing? In other words, how do you know it is #2 and not one or all of the others?
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Old 05-24-2012, 02:56 PM   #9
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Default Re: #2 missing

Quote:
Originally Posted by newshirt View Post
Perhaps a silly question: what instrument or method did you use to determine that #2 wasn't firing? In other words, how do you know it is #2 and not one or all of the others?
Good question and in addition to Marks questions in #6 we should learn a lot. It's best to short the plugs one at a time using a screwdriver to short to ground, rather than pulling the straps away, which can lead to coil failure.
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Old 05-24-2012, 08:53 PM   #10
louieglen
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Default Re: #2 missing

I use a screwdriver and short the plugs one at a time, It isn't a driver, it had been setting for a while, but I have pulled the manifold,valve cover, and nothing is amiss that I can find.
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Old 05-24-2012, 11:42 PM   #11
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Default Re: #2 missing

You said there was nothing amiss that you could find,but in your first post there was a miss---LOL Do you have the same point gap on all 4 lobes of the cam?
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Old 05-25-2012, 02:17 AM   #12
Tom Wesenberg
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Default Re: #2 missing

A slow to close valve will show up on a vacuum guage with the engine running, but won't show up on a compression guage at cranking speed. Ethanol gas can cause sticking valves, and Sea-Foam will help to correct that.
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Old 05-25-2012, 08:08 AM   #13
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Default Re: #2 missing

Quote:
Originally Posted by Tom Wesenberg View Post
A slow to close valve will show up on a vacuum guage with the engine running, but won't show up on a compression guage at cranking speed. Ethanol gas can cause sticking valves, and Sea-Foam will help to correct that.
x2 on that!
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Old 05-25-2012, 08:27 PM   #14
louieglen
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Default Re: #2 missing

After pulling the head, and getting a closer look I found that the intake valve keeper was broken letting the valve sit on top of what was left. Thanks for all of your help
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Old 05-25-2012, 10:50 PM   #15
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Default Re: #2 missing

This sounds like one more instance of modern 'improvements" that create problems.Ive never heard of original retainers breaking on mushroom stem valves.
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Old 05-26-2012, 03:33 AM   #16
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Default Re: #2 missing

good to hear it was fairly painless
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Old 05-26-2012, 11:27 AM   #17
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Default Re: #2 missing

Quote:
Originally Posted by columbiA View Post
This sounds like one more instance of modern 'improvements" that create problems.Ive never heard of original retainers breaking on mushroom stem valves.
I had never heard of the "mushroom" breaking off until this:
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