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'41 has intermittent starting problem


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Today, for only the second time in three months, all of sudden my '41 would not start.  Fortunately, I was only a few blocks from my house and had parked at the top of a slight downgrade.  So I jump started it without a problem and went home.  As soon as I got it in the garage, I shut it down and tried to start it again.  It fired up completely normally.

 

Here's what I can tell you about the two times this has happened:

 

1.  Both times were on local short trips around town.  After behaving normally, all of sudden I go to start the car and it behaves as if the battery were low -- i.e., it barely turns over a few times and then the starter motor stops and I get nothing.

 

2.  It does not appear to be the battery.  I happened to have a voltmeter with me today, and the battery was showing 6.2 volts at the time that it wouldn't start.  After the first time this happened, I took my car to a battery shop and they did a load test that it passed with flying colors.  Both the first time and today, as soon as I got the car safely back in the garage, it started normally.  It has run and started completely normally in the three months between incidents.

 

3.  Nor does it appear that there's anything wrong with the charging system.  The charge indicator behaves normally, and the battery maintains a full charge without a problem even if I don't drive the car for a few weeks.

 

4.  After the first time, I thought there might be a weak connection somewhere in the starting circuit so I removed the battery cables and thoroughly cleaned the contacts and made sure all terminals were tight.  As I said, it has started normally since then until today.

 

So ... what do the professors say?  To my uneducated eye, everything seems to point to the starter motor.  When a starter motor begins to fail, is there a kind of Russian Roulette effect where there's just one bad position of the commutator and brushes, and if the starter happens to stop at that point it won't start again?  I'm clearly just guessing here -- I'm curious if that could be the explanation for this particular symptom.  Any assistance would be most appreciated, including any ideas for further diagnostic testing that would focus on the starter motor.

 

Neil

 

 

 

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You need to do an amperage draw on the starter motor. Could be a bad ground through the starter. There are other possibilities that are unlikely if the car has been fine in the past. 

Edited by edinmass (see edit history)
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Do you have one of these cutoffs on your battery? My 1939 Roadmaster had one. The car was very slow to turn over once it warmed up. I thought it was either starter drag or a bad battery, but the battery checked out fine. The cables are large diameter. The problems went away when I removed the cutoff.

IMG_20210722_165514414.jpg

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47 minutes ago, edinmass said:

You need to do in amperage draw on the starter motor. Could be a bad ground through the starter. There are other possibilities that are unlikely if the car has been fine in the past. 

 

Thanks, Ed.  I will explore that avenue as soon as I get some help on how to do it.  (I know from another thread that you are in the pool, so I don't want to disturb you.) 😄

 

4 minutes ago, BuickBob49 said:

Do you have one of these cutoffs on your battery? My 1939 Roadmaster had one. The car was very slow to turn over once it warmed up. I thought it was either starter drag or a bad battery, but the battery checked out fine. The cables are large diameter. The problems went away when I removed the cutoff.

 

Well, as a matter of fact, I have that exact cutoff switch.  The first suggestion I got when this happened the first time back in April was that the cutoff switch was the culprit.  But I took it apart and made sure it was clean, and I couldn't figure out how it could possibly cause an intermittent problem like this.  But getting rid of it is certainly a very simple thing to do!  Thank you for the help.

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33 minutes ago, neil morse said:

Well, as a matter of fact, I have that exact cutoff switch.  The first suggestion I got when this happened the first time back in April was that the cutoff switch was the culprit.  But I took it apart and made sure it was clean,

 

Agree to get rid on the cutoff switch.  I would guess that your problem will go away.  If you want to have a cutoff switch, buy a good racing cutoff switch from Summit Racing.

Edited by Larry Schramm (see edit history)
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1 hour ago, Rock10 said:

Heat soak on the solenoid switch?

 

Can you spell that out a bit?  I'm not understanding it, but I'm not well-educated on the electrical system.

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Heat increases resistance, causing voltage and amperage drop. The longer the wire, the more the drop. It also affects the starter field coils and armature. They started fine when new, you just need to eliminate the good components, and focus on finding the voltage issue.

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27 minutes ago, neil morse said:

 

Can you spell that out a bit?  I'm not understanding it, but I'm not well-educated on the electrical system.

When the engine gets hot it transfers heat to the starter and solenoid. As the solenoid gets older it's more susceptible to failure while hot. Usual sign would be unable to engage the starter to the flywheel and no starter function until the can cools down. Since it just began happening and the trips were short, that might be remote.

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  • 2 weeks later...

Something you can do right now is check the action of the vacuum advance plate. Just take the distributor cap off and rotate the plate in the direction of the advance lever. It should snap right back when released. If it doesn't the plate will stay advanced on those brief engine shut off times. Too much advance will make the engine grunt and fail to start giving the symptoms of an electrical problem.

Check the oiler and lubrication point for the breaker plate if it doesn't have a crisp action.

 

My first experience with this was a complaint that the Buick started fine when it had been sitting. Then the owner drove to the gas station, put in gas, and the car grunted like the battery was low. I lubed the blackened, dry cork pad under the plate and all was fine again.

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On 8/1/2021 at 10:48 AM, FLYER15015 said:

Neil,

Have you checked the vacuum switch on the carb ?

Sometimes they get sticky, (intermittent) before they quit altogether.

 

Mike in Colorado

 

Thanks for the suggestion.  The vacuum switch on the carb has actually been disabled on my car and it has a push button under the dash instead.  I decided to leave it that way when I got the car since I really don't care about that level of authenticity, and it seemed like a potential trouble spot anyway.

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On 8/1/2021 at 12:26 PM, 60FlatTop said:

Something you can do right now is check the action of the vacuum advance plate. Just take the distributor cap off and rotate the plate in the direction of the advance lever. It should snap right back when released. If it doesn't the plate will stay advanced on those brief engine shut off times. Too much advance will make the engine grunt and fail to start giving the symptoms of an electrical problem.

Check the oiler and lubrication point for the breaker plate if it doesn't have a crisp action.

 

My first experience with this was a complaint that the Buick started fine when it had been sitting. Then the owner drove to the gas station, put in gas, and the car grunted like the battery was low. I lubed the blackened, dry cork pad under the plate and all was fine again.

 

Thanks, I will check the vacuum advance situation, but it seems unlikely that that's the problem based on your description.  The symptom on my car (the two times it has happened) is not a "grunt" and failure to start.  It's a few slow turn overs and then zero, as if the battery were completely dead.  I have removed the cut-off switch as discussed above, and so far the problem has not reoccurred.  (However, it previously went three months between occurrences, so I know that doesn't prove anything.)  We shall see.

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