Bad starter motor question...


Old 03-27-20, 07:03 AM
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Bad starter motor question...

Is it possible for a (bad) starter to spin the engine without compression but unable to do so under load? In other words, do they fail intermittently/become weak or do they fail open?

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Old 03-27-20, 07:12 AM
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Your description sounds more like a weak battery than bad starter. Have a good one. Geo
Old 03-27-20, 07:16 AM
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As far as I know they can go either way but more likely to totally fail.
But I am not a mechanic.

I would be more likely to suspect a bad starter relay or a weak battery re: the starter motor is not getting enough juice. So I would check the battery voltage, the voltage on the input of the relay and the voltage on the output.
Do this while trying to start the vehicle.
Could also be a bad ground at the starter motor.
Old 03-27-20, 07:39 AM
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In my case I am seeing approx 6volts at the starter post when trying to crank.Battery and grounds are good. Im going to blame engine compression but have to rule out the starter first.


Last edited by billyjoey; 03-27-20 at 08:42 AM.
Old 03-27-20, 10:40 AM
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What engine is this on? If OHV, have you adjusted the valves?
Old 03-27-20, 10:46 AM
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It engages and spins the flywheel? How could it not have compression, assuming all the plugs are tight.
Old 03-27-20, 11:00 AM
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It's an electrical motor so yes, they can get weak.

In other words, do they fail intermittently/become weak or do they fail open?
Yes & yes. Typically if they become weak, and you still crank and crank eventually they can fail open. They can also fail open from the get go.

6 Volts??? How are you testing your battery? To do it accurately, you need to load test it. Is that how you've tested it? (I'm assuming this is not some unique car). If a normally 12 volt battery is very weak, you can draw down the voltage when putting a load on it, yet still show it has 12 volt from a voltmeter. (Actually should show slightly higher than 12 volts but that discussion can wait).

I'm tending towards Geo's diagnosis with the info given so far....
Old 03-27-20, 04:02 PM
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A starter can slow down. We used to say the starter is "draging". In my experience a starter would either drag, lock up or go completely out.

So I agree... yes ... & yes.
Old 03-28-20, 04:07 AM
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Had this same problem last year. Adjust the valves, solved my problem. Adjust them a little on the tight side.
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