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1937 Roadmaster cranking problem


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I had the starter professionally rebuilt in the '37 Roadmaster over the winter, and also put a new battery in it. Today I went to start the engine and it cranks normally for a few seconds, then very slowly just barely turning over for a couple of seconds, and then back to normal, as if the timing was way off, but it's not. The car ran great the last time I drove it which was about a month ago. I removed the battery and charged it up to be sure it was fully charged, and when I touched the positive battery cable to remove it, it nearly burned my fingers, it was so hot.

 

Doesn't this sound like a short or a bad field inside the starter?  I probably haven't cranked it 5 times since I had the starter rebuilt and it cranked normally. Battery cable is not shorting out on anything. Suggestions? Take the starter off and send it back to the rebuilder? I have done business with this rebuilder for 30 years and have never had a problem with their work.

 

Pete Phillips, BCA #7338

Leonard, TX.

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I would make sure that where the starter bolts up to the bell housing, is clean and paint free. If the starter and/or bell housing was painted you would be surprised how much that interferes with grounding of the starter. I would also make sure that the starter mounting bolts are nice and clean. I would use a wire wheel to clean any old paint off of the threads and shoulders of the bolts. Other than those, I would make sure the battery cables are in perfect shape. Sometimes you will find that an old cable looks good at a glance, but has problems. If those don't solve it, I would send the starter back and have them recheck it. 

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Was the entire cable hot? Or just an end? If it heating up right at the post, the outside of the post or the inside of the hole is dirty (scrape). If that doesn't fix it, and it still gets hot at the post the connection where the clamp is crimped or cast to the wire of the cable is bad. If you can isolate a spot that gets hot, the problem lies there.

 

If the whole thing is getting hot, maybe the starter draws too much current and needs attention. That could also be the engine's fault if it drags too much, but that is less likely.

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Most everything has already been said. One other possibility is a bad battery. It is possible that the internal connection to the positive post is bad. Best test for this is to try a known good battery if you can.

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What gauge are the battery cables? If the cable is hot along its whole length then either the current draw is excessive or the cable gauge is too small. I use AWG 00 gauge cables on my 38 special and they run cool and the engine cranks beautifully. The drop across the positive cable which is about 18" long is less than 0.1V during cranking.

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9 hours ago, avgwarhawk said:

I would suspect the starter.

Chris,

That's what I'm suspecting now, because I cleaned all of the wires, junctions, and battery connections this morning, and still the same problem--no change at all.

 

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13 hours ago, Pete Phillips said:

Chris,

That's what I'm suspecting now, because I cleaned all of the wires, junctions, and battery connections this morning, and still the same problem--no change at all.

 

 

What gave it away for me is the very hot cable after attempting to turn over the starter.  Drawing a lot juice resisting wanting to spin.     

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  • 2 weeks later...

The problem persists. I took the starter off and carried it back to the rebuilder who looked at it and said there was nothing wrong.

There is no paint on the bell housing where the starter sits--it is clean, bare metal; same for the flange on the starter body where it contacts the bell housing. I did find a little bit of light corrosion on the solenoid connections where the small wires from the starter switch connect. 

Fuel pump started leaking, so now it will be awhile before I can try cranking it again, while I wait for a fuel pump rebuild kit.

Pete Phillips, BCA #7338

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Try cranking it with all the spark plugs removed and even the fan belt removed, it will draw less current from the battery and should help it spin easier and faster. 

Also, disconnect the fuel line from the carb so you dont have fuel flying everywhere.

 

 

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Posted (edited)

While you are waiting, you could also disconnect and plug the fuel supply line from the tank. Then you could continue testing.

 

I understand the cables are getting hot along their entire length, it that correct?

 

The positive cable hooks directly to the starter solenoid post, correct? No cutoff switches or anything like that?

 

Where does the negative cable connect?

 

Oh one more thing, a 1937 starter has an adjustment for the pinion depth. With the starter on the bench, you have to hold the outer diameter of the solenoid plunger (not the arm or anything coming from the center) back solid as far as it will go, and measure the distance from the tip of the drive gear to the starter nose casting. The shop manual has the dimension. Probably 1/8", but don't take my word for it. If the solenoid has a boot you will probably have to remove it to check this. The solenoid plunger is threaded to adjust. You have to get the plunger out of the solenoid to turn it, probably by removing the solenoid and leaving the plunger attached to the starter. Since the plunger is keyed, it moves in increments of one turn.

 

Edited by Bloo (see edit history)
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I would also try swapping to a known good set of battery cables from another car. Perhaps there is a cable problem that is not readily apparent.

 

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1 hour ago, MCHinson said:

I would also try swapping to a known good set of battery cables from another car. Perhaps there is a cable problem that is not readily apparent.

 

Could check cables for resistance with an ohmmeter.

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With the starter on a bench and connected to a good 6V battery what happens? [If possible to do] But does not check performance under load.

Has it been rebuilt as a 6 volts?  But may be no difference 6-12.

Is it meshing correcting with the pinion-flywheel? Buick changed the pitch over the years.

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On 4/21/2021 at 1:25 AM, Bloo said:

Was the entire cable hot? Or just an end? If it heating up right at the post, the outside of the post or the inside of the hole is dirty (scrape). If that doesn't fix it, and it still gets hot at the post the connection where the clamp is crimped or cast to the wire of the cable is bad. If you can isolate a spot that gets hot, the problem lies there.

 

If the whole thing is getting hot, maybe the starter draws too much current and needs attention. That could also be the engine's fault if it drags too much, but that is less likely.

The entire cable was hot.

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It is definitely drawing too much current then. That should make it easy to find, but unfortunately it doesn't, because a DC electric motor draws maximum current at 0 rpm. If the motor runs but fails to spin up for any reason, the current is likely to run high.

 

3 things I would check:

 

1) The solenoid adjustment I mentioned above. If it's far enough off the overrunning clutch will drag on the flywheel, and the drive gear will machine metal off of the starter nose casting.

 

2) There are 2 windings on the solenoid. If one is burned out, the solenoid will chatter on the starter contacts and since the copper bolts in the solenoid are not making good connection, everything gets real hot. With everything disconnected from the starter solenoid, including the copper strap that goes to the starter motor, you should have continuity from a.) the small post on the solenoid itself (not the little relay) to the large post that normally connects to the starter motor and b.) from the same small post to ground (the solenoid case).

 

3) Pull the dust cover strap off off the back of the starter and look at the brushes and commutator. See if the armature's commutator has been undercut (between the copper segments). It should NOT be. If I remember correctly the 37 shop manual says to undercut it. I am a little confused how that could have been true in 1937. It isn't true today. I suspect it is a mistake. You do undercut armatures on generators, but not starters. Starter brushes are made of copper and will fill the slots with copper shorting out the armature. If this is what has happened, you will find the slots full of copper, and that explains the slow running and excess current draw. You can fix it temporarily by taking the starter apart and cleaning the slots out, but if the commutator is undercut it will just do it again.

 

I have encountered both 1) and 2) on straight 8 Buicks. Number 3) is also a good possibility. 

 

Does your ground cable go to the frame or to the engine/trans?

 

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One thing that has not been mentioned is something binding in the engine itself. I would take out the spark plugs, disconnect the distributor wire at the coil (this is not really needed, but I like to eliminate anything sparking when I do not need it)!  Next lay a towel or shop rags over the spark plug holes and then try cranking her over. If she cranks smoothly let her crank for for 15 seconds or so and then look at the towel/rags to see if anything got blown out, like water etc.  If it checks out good then I think you are back to the starter or solenoid.  Just thinking out loud here.....

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