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Old 10-18-2020, 12:39 PM   #1
Joe Immler
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Default '41 won't crank when hot

My 1941 starts with no more than 3 rotations. However, drive it for some miles and shut off. If the radiator temperature is above 180 degrees or so the starter won't crank the engine. Push the starter button and all I get is a clunk no cranking. Battery is charging fine. Starter and generator have been rebuilt.
Regulator and condenser check out fine. Open the hood and let it cool down and it fires right up. (?)
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Old 10-18-2020, 12:53 PM   #2
marko39
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Default Re: '41 won't crank when hot

When this happens I would the voltage at the starter terminal to make sure you are getting proper voltage. This will narrow it down.
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Old 10-18-2020, 12:57 PM   #3
rotorwrench
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Default Re: '41 won't crank when hot

Could be a starter problem. Broken or cracked wires like to separate when hot. I would also pull the distributor and do some inspection & service with the flyweights to make sure the spark is retarding all the way for starting. If a person cranks the starter with the ignition off, it would let you know if it's trying to kick back or not. If it still won't turn over then it's time to start checking all the starter system components. A bad relay, a bad starter cable, or any problem with battery or its connecting cables could also cause starting problems. Stuff wears out and when it does, it starts telling you there is a problem. Check the easiest things first.
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Old 10-18-2020, 01:21 PM   #4
RKS.PA
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Default Re: '41 won't crank when hot

Joe, did you just rebuild the engine, or did this just pop up on an "old reliable"?
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Old 10-18-2020, 01:23 PM   #5
Joe Immler
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Default Re: '41 won't crank when hot

marko, I will check it out.
rotor, Good ideas. Never thought about the distributor. Also, never tried the starter with the ignition off.
Thanks, guys.
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Old 10-18-2020, 02:15 PM   #6
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Default Re: '41 won't crank when hot

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Clean and properly sized battery and starter cables can be an issue. What size cables are you using?
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Old 10-18-2020, 03:26 PM   #7
Joe Immler
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Default Re: '41 won't crank when hot

RKS The engine was rebuilt 3 years ago. Has about 4,000 miles on it.
JSeery The cables are from C&G I am not sure of the size.
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Old 10-18-2020, 04:13 PM   #8
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Default Re: '41 won't crank when hot

Quote:
Originally Posted by Joe Immler View Post
RKS The engine was rebuilt 3 years ago. Has about 4,000 miles on it.
JSeery The cables are from C&G I am not sure of the size.
Well, the cables are most likely not a problem.
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Old 10-18-2020, 08:14 PM   #9
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Default Re: '41 won't crank when hot

Not to sound like a wiseguy, but please define "rebuilt starter". All too often they get opened up, checked for brush wear and put back together. Except for a loose/broken wire or terminal screw, the usual problem is tracked down to worn bushings. Brushes almost never wear out. The front and rear bushings always wear out and are hard to detect. You can not just slide the armature into the bushing and rock it. The fit needs to be perfect. Very common problem in the "won't crank when hot". If it does not have new bushings then it is not rebuilt. NOS rear plates with bushing installed are available. Front bushings are easier to replace as they are not blind like the rears.
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Old 10-18-2020, 08:27 PM   #10
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Default Re: '41 won't crank when hot

Quote:
Originally Posted by Floyd View Post
Not to sound like a wiseguy, but please define "rebuilt starter". All too often they get opened up, checked for brush wear and put back together. Except for a loose/broken wire or terminal screw, the usual problem is tracked down to worn bushings. Brushes almost never wear out. The front and rear bushings always wear out and are hard to detect. You can not just slide the armature into the bushing and rock it. The fit needs to be perfect. Very common problem in the "won't crank when hot". If it does not have new bushings then it is not rebuilt. NOS rear plates with bushing installed are available. Front bushings are easier to replace as they are not blind like the rears.
Ditto. A fresh starter always makes a big difference. The larger gauged 6 volt battery cables are necessary too.
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Old 10-19-2020, 08:23 AM   #11
Joe Immler
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Default Re: '41 won't crank when hot

I took the starter to a trusted rebuilder but don't know what all was done. I will pull the
starter and ask for new parts to be installed. It may be awhile until I get to it but will let you know.
Thanks, all of you for the help. Why I love The Barn.
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Old 10-19-2020, 08:51 AM   #12
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Default Re: '41 won't crank when hot

Quote:
Originally Posted by Floyd View Post
Not to sound like a wiseguy, but please define "rebuilt starter". All too often they get opened up, checked for brush wear and put back together. Except for a loose/broken wire or terminal screw, the usual problem is tracked down to worn bushings. Brushes almost never wear out. The front and rear bushings always wear out and are hard to detect. You can not just slide the armature into the bushing and rock it. The fit needs to be perfect. Very common problem in the "won't crank when hot". If it does not have new bushings then it is not rebuilt. NOS rear plates with bushing installed are available. Front bushings are easier to replace as they are not blind like the rears.
Correct; this was called back then "ya starters ah draggin" the rear bushing
with a die grinder just whittle it thin just short of the casting, and pop it right out with a pic. These days one has to be careful because we trust. My son
bought a Model A rebuilt carb. tillison. one year its pouring gas all flooded up
I took it apart. Looks like it was glass beaded. The float all soldered up and
full of gas. there ya go - why? bought new float from Tams & off he went. So Floyd is right. Stick a new bend-ex new brushes call it rebuilt put on ebay
so there you go ugg
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Old 10-19-2020, 09:23 AM   #13
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Default Re: '41 won't crank when hot

Also make sure your ground/hot connections are shiny clean and tight. Use steel wool/sandpaper to clean up the connection mating surfaces. When everything is done I lightly spray the outside of my connections with Fluid Film to keep it from corroding.
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Old 10-19-2020, 10:44 AM   #14
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Default Re: '41 won't crank when hot

If the starter is still in the car and you experience this again, try rapping on the starter with something and see if it starts. If it does it would indicate worn bushings, binding the rotor as mentioned in earlier posts
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Old 10-19-2020, 11:35 AM   #15
JSeery
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Default Re: '41 won't crank when hot

Quote:
Originally Posted by Joe Immler View Post
I took the starter to a trusted rebuilder but don't know what all was done. I will pull the
starter and ask for new parts to be installed. It may be awhile until I get to it but will let you know.
Thanks, all of you for the help. Why I love The Barn.
Might talk to the rebuilder before you pull it just to see what he has to say.
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Old 10-19-2020, 11:53 AM   #16
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Default Re: '41 won't crank when hot

I was having the same problem your having, mine turned out to be the connections on the ballast resistor. I cleaned them and made sure they were tight. The resistor is located under the dash to the left of the steering column. It is a wire wound resistor and mounted to a fuse block. It regulates the voltage to the coil, if it gets hot it will not pass the correct voltage to fire the coil. After it cools off it works fine. I would check the coil wire when this happens to see what if any voltage your getting to the coil, should be about 3 volts. Al
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Old 10-24-2020, 09:30 AM   #17
Joe Immler
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Default Re: '41 won't crank when hot

GOT IT ! Well, grumpy it turned out to be the resistor. I also had the starter checked by another re builder and he found a worn bushing. Re installed it but still wouldn't crank when hot. Checked the resistor and Bingo!
Thanks everyone for your advise.
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Old 10-24-2020, 09:36 AM   #18
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Default Re: '41 won't crank when hot

Sorry folks. What does the resistor have to do with the starter circuit? I thought the resistor was only in the ignition circuit to control voltage to the coil.
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Old 10-24-2020, 10:06 AM   #19
JSeery
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Default Re: '41 won't crank when hot

Think this is because (at least to me) the original post was not clear about the issue. I was under the assumption that the starter was not turning over correctly when hot. Seems the issue was more that the engine was not firing when the vehicle was hot. Now, they are somewhat related, when the starter is cranking it is pulling the voltage available to the coil, via the ballast resistor, down. If the starter is pulling more current when the engine is hot, then even less voltage is available to the coil. Add in a bad ballast resistor and that is how they get related to a no-start condition.

On some later 12v vehicles this was addressed with the starter solenoids that use a ballast resistor by-pass whenever the starter in engaged.
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Old 10-24-2020, 10:19 AM   #20
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Default Re: '41 won't crank when hot

Thanks J. Now it makes sense.
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