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davh 
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Joined: 27 Apr 2016
Location: Kansas
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 Topic: Allis B with #3 cylinder missing
Posted: 22 Sep 2016 at 12:33pm |
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I have good compression and fire to the plug on #3 cylinder. Have replaced spark plug 2 times. Will not take off and fire. Tractor starts but misses on #3. Have not changed cap and wires and am using Pertronix pointless ignition. Any ideas?
Thx. davh
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gcnoyes
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Joined: 21 Sep 2014
Location: Hesperus co
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Posted: 22 Sep 2016 at 12:59pm |
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first swap plug wires between 2 and three if the will reach and see if the problem moves to #2. if it does you have a bad plug wire. if not it could be the distributer cap but I would check compression on on #3 while you have the plug out.
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steve(ill)
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Joined: 11 Sep 2009
Location: illinois
Points: 86529
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Posted: 22 Sep 2016 at 4:35pm |
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yes, either you have two wire switched, or the cap has a crack between #3 and another.
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Like them all, but love the "B"s.
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CTuckerNWIL
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Joined: 11 Sep 2009
Location: NW Illinois
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Posted: 22 Sep 2016 at 4:45pm |
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You could possibly also have a carbon arc inside the cap, letting the spark find an easier path to ground than going thru the plug.
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Dusty MI
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Joined: 13 Sep 2009
Location: Charlotte, Mi
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Posted: 22 Sep 2016 at 6:45pm |
Most likely firing order is 1-2-4-3. Someone will correct me if I'm wrong.
Dusty
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917 H, '48 G, '65 D-10 series III "Allis Express"
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Dick L
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Location: Edon Ohio
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Posted: 22 Sep 2016 at 7:58pm |
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Could also just be a bad plug. When I was farming with my Oliver 1850's and 1650 I bought sets of eight new plugs each spring for 6 cylinder tractors. After a short time under load I would loose a plug on one or two of the tractors. Put in a new plug and back at it. I have had the problem with all makes of plugs. I have had plugs in a tractor for years and not go bad also. If all else fails switch plugs to see if the problem stays on the same cylinder.
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davh
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Joined: 27 Apr 2016
Location: Kansas
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Posted: 23 Sep 2016 at 6:18am |
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Thanks for the replies. #3 has good compression so I'm pretty sure it has to be ignition. I have changed the plug 2 times already but not the cap or wires. Oddly enough the plug has fire when I had it pulled and grounded to check spark. Going to change wires and then cap and see if that solves the issue. Thanks again, davh
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Allis dave
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Location: Northern IN
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Posted: 23 Sep 2016 at 6:50am |
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I've heard people say plugs will fire easier out in the open then when under compression, so pulling the plug and watching it spark doesn't always mean you have spark.
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davh
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Location: Kansas
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Posted: 23 Sep 2016 at 7:13am |
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I will change the plug again and check that out also. Thanks, davh
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Gerald J.
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Joined: 12 Sep 2009
Location: Hamilton Co, IA
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Posted: 23 Sep 2016 at 11:16am |
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The plug gap is fairly large for the voltage at 100 psi compression pressure. Its an easy gap in air. A more valid check is to look for the bare end of the plug wire to spark at least 3/8 of an inch, preferably 1/2" in air with a kind of fat blue spark. Yellow spark shows a bad condenser.
Gerald J.
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Dick L
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Posted: 23 Sep 2016 at 11:23am |
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Another trick is to hold the plug wire about 1/8" away from the plug to see if it will pick up.
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KenBWisc
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Posted: 23 Sep 2016 at 12:04pm |
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Correct me if I'm wrong but can't you have good compression and spark but have no fuel due a valve not opening? When I lost #3 it was because the rocker arms were wore out and one wasn't making contact with a push rod.
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'34 WC #629, '49 G, '49 B, '49 WD, '62 D-19, '38 All Crop 60 and still hunting!
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Bill Long
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Location: Bel Air, MD
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Posted: 23 Sep 2016 at 12:28pm |
You know I keep forgetting that these tractors that I grew up working on are now at least almost 60 years old. And yes strange things that I never anticipated in the 50's can and will happen to them. It seems you have covered all the bases with the exception of rotor, cap, and wire. May want to try them first since they require less work. If no success then go to the valves. Another thought, Check the manifold to be certain the intake is sealed so that the number three does not draw in too much air. In any event, I look forward to hearing reports of my favorite running well again. Good Luck! Bill Long
Edited by Bill Long - 23 Sep 2016 at 12:29pm
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Brian Jasper co. Ia
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Posted: 23 Sep 2016 at 12:57pm |
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Ken has a valid point. A worn out intake lobe can give you a dead miss but still give a good compression reading. I would be looking at the cap and wires first since they're the easiest and most likely to fail.
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"Any man who thinks he can be happy and prosperous by letting the government take care of him better take a closer look at the American Indian." Henry Ford
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Chalmersbob
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Location: Pennsylvania
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Posted: 23 Sep 2016 at 10:03pm |
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check for a bent push rod on # 3 if all else fails. Bob
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4 B's, 1 C's,3 CA's, 2 G's WD, D14, D15, B-1, B10, B12, 712S,
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allisguy.11
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Posted: 24 Sep 2016 at 8:41am |
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had one that was doing this last week on number one after I replaced points. turns out my gap was too wide (just did them quick by sight).... gapped them right and ran like a champ. after I changed wires, plugs, cap of course.... shoot
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Dick L
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Posted: 24 Sep 2016 at 9:26am |
Engines running are not a mystery operation. Hard to understand how it could still be missing if everything that has been suggested has actually been checked. The bent push rod or a push rod not under the rocker would be a good call if it is actually firing at the plug and it is firing on time on the other three. This engine can sound like it is running on three cylinders with plug wires out of order.
I stress details that get missed from time to time because they must be paid attention to have a successful outcome. Also because when I have had a problem it has been because I missed a detail.
Example:
I worked thru a Saturday night to finish building a stroker pulling engine for a Sunday pull. At day break I started the engine and had a miss. After changing plugs around I went in and eat breakfast still having a miss. While eating I remembered after starting and re-torqueing the head I had not checker the valve lash. I reset the rockers and loaded the tractor with the miss gone.
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Gerald J.
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Posted: 24 Sep 2016 at 10:51am |
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Wrong point gap can result in no spark when the distributor cam is worn off center and definitely with changed timing which is why the op manual says set the point gap, then set the timing.
Gerald J.
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davh
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Location: Kansas
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Posted: 26 Sep 2016 at 7:35am |
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Changed plug and wire and seems to fix problem. That was the 3rd plug but 1st wire. I had spark with old wire when I had plug out before. Still a bit of a mystery but it works now. Ran the tractor quite a while and started and stopped and it continues to sound good. Thx for all the thoughts. davh
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