"B" engine problem
Printed From: Unofficial Allis
Category: Allis Chalmers
Forum Name: Farm Equipment
Forum Description: everything about Allis-Chalmers farm equipment
URL: https://www.allischalmers.com/forum/forum_posts.asp?TID=162672
Printed Date: 28 Jun 2024 at 5:33am
Software Version: Web Wiz Forums 11.10 - http://www.webwizforums.com
Topic: "B" engine problem
Posted By: wigtrain
Subject: "B" engine problem
Date Posted: 10 Jul 2019 at 7:46am
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Here' hoping some of you have some valid suggestions. I have B that has decided to not run properly. It went from an intermittent miss to almost not running at all. Why during hay season who knows. The tractor is a 1940 and has worked it's entire life. I do not know how many times it's been rebuilt. As it is now it will only run a full throttle with the choke almost closed. Here's what has been checked so for. The compression is 89 pounds or slightly better on all 4 cylinders. The fuel supply at the carb will run a full stream for as long as the shutoff is open. The carb has been rebuilt twice and also swapped for a different one from another tractor. The mag has been swapped 4 times with others. 3 mags rebuilt by me, one rebuilt by Steve at B&B. The exhaust/intake has been removed and a new gasket installed. Plugs have been changed several times. Any suggestions on where to go next ? It difficult to get haying done and be down a tractor but we are managing. jim wiggin ------------- Jim Wiggin |
Replies:
Posted By: WF owner
Date Posted: 10 Jul 2019 at 7:58am
| I am betting that you have either an obstruction in the fuel system, possibly the inlet of the sediment bowl or a dirty carb. |
Posted By: Gerald J.
Date Posted: 10 Jul 2019 at 9:45am
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The shop manual should be a help. http://geraldj.networkiowa.com/Trees/Allis-Chalmers-G-B-C-CA-Service.pdf" rel="nofollow - http://geraldj.networkiowa.com/Trees/Allis-Chalmers-G-B-C-CA-Service.pdf There are many things that have to be right for an engine to run as planned and any one of those things can be the cause of poor running. Gerald J. |
Posted By: chaskaduo
Date Posted: 10 Jul 2019 at 10:13am
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Could a valve or two adjustments loosened up? ------------- 1938 B, 79 Dynamark 11/36 6spd, 95 Weed-Eater 16hp, 2010 Bolens 14hp |
Posted By: Dick L
Date Posted: 10 Jul 2019 at 11:57am
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Do you have a different manifold to swap with the one on the tractor? If you have a full stream at the carburetor, have changed carburetors that have been rebuilt, installed a new manifold gasket and still need a lot of choke I would guess you have an internal manifold leak. Here is a picture of an manifold I sawed into sections to find an internal leak caused by a core shift when cast. 
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Posted By: wigtrain
Date Posted: 11 Jul 2019 at 4:29pm
Thanks for all of the help. Today I swapped out the manifold from one of my other B's that was running well. No change with the problem. At this point I'm so frustrated I may turn it into a parts tractor to help keep my others running. Maybe I'll feel better tomorrow  ------------- Jim Wiggin |
Posted By: Dick L
Date Posted: 11 Jul 2019 at 7:03pm
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Never give up! Instead use it as a challenge that it will not stump you long. Having a full stream of gas at the carburetor and it being able to run wide open would mean you are getting gas thru the power jet it needs using the choke. Normally if you have an obstruction you would be able to run at idle and the obstruction would keep it from running wide open. You have proven that you do not have an air intake leak. You have proven you have fuel at the carburetor. You have proven you have compression. You have proven you have spark. How close have you proven it is in time? Have you proven the firing order is correct. 1243 This engine will run with two wires crossed up. Not well but will run. If it has the Zenith non adjustable carburetor the idle circuit might be plugged or not adjusted. an upside down gasket can plug that. Just some things to think about as you trace thru the details. |
Posted By: DougS
Date Posted: 11 Jul 2019 at 7:15pm
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I would lean toward a clogged carb jet, since it slowly started to run worse. If the mag is a little loose, it could have gone out of time. Are you using new spark plugs? Just because the plugs look good doesn't mean they are. |
Posted By: Boss Man
Date Posted: 11 Jul 2019 at 7:41pm
| Did you do the compression test with all the plugs out? When was the last time the plug wires were changed? Do you have copper core wires? |
Posted By: DaveKamp
Date Posted: 11 Jul 2019 at 10:52pm
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I'll second Boss's note... copper (not graphite) wires for a magneto... resistance wires will drive the magneto's voltage WAY TOO HIGH, and it'll internally short the magneto's coil. Start it up after dark, and look around each plug wire, and the magneto... do you see any 'fire' where there shouldn't be 'fire'? ------------- Ten Amendments, Ten Commandments, and one Golden Rule solve most every problem. Citrus hand-cleaner with Pumice does the rest. |
Posted By: festus51
Date Posted: 11 Jul 2019 at 10:59pm
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If it runs using the choke it sounds like not enough gas is getting through. I will go with a gas circuit being somewhat plugged up on the interns of the carb ------------- We the unwilling Led by the unqualified Doing the impossible for the Ungrateful |
Posted By: B26240
Date Posted: 12 Jul 2019 at 6:07am
| Whatever you end up finding keep us posted as that is how we all learn. I had a Farmall H that had a wiered miss when Idling and would spit a little fire out the exhaust. It turned out to be a bad manifold. |