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Mark in Iowa 
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Joined: 22 Dec 2009
Location: Iowa
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 Topic: AC B starting when hot issue
Posted: 26 Jun 2017 at 9:03pm |
I have a '39 B, hand crank tractor. It starts well when the engine is cold, but I have difficulty starting it when the engine is hot .
Is it likely the coil in the magneto?
I apologize if this has been asked before.
As always thanks for your help, Mark
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Hubert (Ga)engine7
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Joined: 12 Sep 2009
Location: Jackson Cnty,GA
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Posted: 26 Jun 2017 at 9:19pm |
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Could be the coil in the magneto or possibly a crack opening up in the intake part of the manifold or just the nature of the beast. The old Wisconsins were just about impossible to start when hot. We would leave the one on the hay baler running when we stopped for lunch.
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Just an old country boy saved by the grace of God.
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CrestonM
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Location: Oklahoma
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Posted: 26 Jun 2017 at 9:43pm |
I thought they were mostly all that way. Mine sometimes is. I know All-Crop combine engines (B125 units) had a petcock on the manifold. I was told that was to allow fresh (cooler, in theory) air into the engine to help it start easier.
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Hubert (Ga)engine7
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Posted: 27 Jun 2017 at 6:47am |
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That petcock was also to allow it to be used to operate a vacuum milker. They were found on a lot of the older B's and C's.
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Just an old country boy saved by the grace of God.
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Ted J
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Location: La Crosse, WI
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Posted: 27 Jun 2017 at 8:14am |
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Yep, when we lost electricity on the farm, we would start up the C and hook the hose to the manifold and finish milking. Funny we never burned that barn down........using kerosene lanterns to milk by......
It's a good memory, but scary now.
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"Allis-Express"
19?? WC / 1941 C / 1952 CA / 1956 WD45 / 1957 WD45 / 1958 D-17
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Bill Long
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Posted: 27 Jun 2017 at 10:33am |
I'm not the expert Steve NJ is but you may want to try the condenser first. Sometimes it will work but usually it is the coil. Remember these units are almost as old as I am. I really don't think when my father sold them in 1939 that they would still be alive and well in 2017. Take good care of my favorite. Good Luck! Bill Long |
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Gerald J.
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Location: Hamilton Co, IA
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Posted: 27 Jun 2017 at 10:48am |
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Could be condenser, coil, points, wires, plugs, shut down switch and its wiring, or impulse start mechanism. Every piece has to work right for starting hot or cold. The impulse start mechanism in the magneto is crucial for starting, but you should be able to detect its working by the clicking from the magneto as each cylinder passes top dead center. There won't be starting spark without it working.
Not to say that fuel can't be a problem with the engine warm, a valve not closing could upset the intake manifold vacuum to make starting difficult. Restricted fuel flow from junk in the screens and lines can make it hard to start and run.
Fact is everything in timing, fuel, and ignitions systems has to work right for the engine to start and run.
Gerald J.
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Brian Jasper co. Ia
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Joined: 11 Sep 2009
Location: Prairie City Ia
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Posted: 27 Jun 2017 at 12:41pm |
BEFORE you start fiddling with the carb, best place to start is with a good tune up. I'd get Standard Blue Streak points and condenser and avoid everything else. I would check with Arnold's if you have one close. The Pella Arnold's had Standard Blue Streak points and condenser for an old Caddy a while back so they should be able to get them. My preference on plugs would be AC Delco. Champion is a 50/50 chance of getting good ones. Get the ignition system up to 100% FIRST, then if it still has a problem address it at that time.
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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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Randy MN
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Joined: 03 Dec 2015
Location: Blaine, MN
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Posted: 27 Jun 2017 at 2:21pm |
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Our 38 B sometimes has trouble starting when hot. I discovered when I removed the oil cup off the air cleaner, it would draw fresh air and start immediately. So I shortened the hose between the carb and air cleaner just a little bit. I have a screw driver in the tool box, loosen the hose clamp and pull the hose towards the carb so I have a small gap to draw fresh air and for 7 years it has been starting on the second crank every time. A little hassle but it only takes me about 1 minute to be on my way. I have been told I might have a plugged air cleaner, but I have done all I can to clean it out. I think with one turn of the crank it just has a hard time drawing air through the 20W oil in the cup. So if you have a flat spot on your manifold to put a petcock, that would probably even be easier.
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34 WC #477, 38 B #1935, 1-116 on steel, #8 7ft dbl action disc, #9 5ft dbl action disc, 295 Chainsaw
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Dick L
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Location: Edon Ohio
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Posted: 27 Jun 2017 at 3:18pm |
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What three things are needed to make an engine to start? It is my understanding that you need spark, fuel and compression.
Do you have a good spark when you are having problems starting?
Do you have fuel when you are having problems starting?
Do you have proper compression?
Checking all three at the time you are having the starting problem will give you the answer.
If you have no spark, a coil that opens up with heat will not give a spark. A condenser that shorts out will cause a no spark problem. A condenser that is open will still give a spark but will cause points to burn. Points that have burned from an open condenser will cause a carbon tit on the points that will cause a no spark problem.
I have never had a coil get hot and restart after cooling very many times before it would not start at all.
In years past I have had starting problems from low compression. My 52 Chevy would take a lot of grinding of the starter before it would start after driving it a quick trip to town. After a valve grind it would pop right off.
Edited by Dick L - 27 Jun 2017 at 3:18pm
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Mark in Iowa
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Joined: 22 Dec 2009
Location: Iowa
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Posted: 27 Jun 2017 at 6:43pm |
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Thanks guys for all great ideas. I will begin my work on the B.
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