Starter Motor spinning in wrong direction?

U

ulfurk

Member
Hey all, I was having some starter problems in my '03 2.5, it simply wouldn't turn over.
No clicking, no spinning, nothing and yet there was plenty of juice in the battery.
Had to be the starter so I pulled it out and indeed it was broken.

The solenoid switch was burnt over and didn't function. I got a replacement and popped it on.
Now the motor got power and the solenoid was doing it's thing. Popped it in and after one very weak start it broke down again.

Out came the starter and now, after opening the motorhousing, I noticed that the brushes were all but gone so I got replacements for those as well.
Popped those in and now the solenoid pulls and the starter turns but when I got it in the car it wouldn't start. I could hear the solenoid clicking and the motor would just spin there.
There was no straining to the sound, it just seemed like it was spinning fairly freely.

At first I thought the solenoid wasn't pushing far enough forward so the starter wasn't engaging the flywheel but I soon discarded that theory.

The next thing that came to mind was that the bendix was broken and couldn't hold up to the torque needed to turn the motor.
I haven't completely discarded this theory, however, I've tried testing the bendix to the best of my abilities using vise and some leverage and I'm no longer convinced the bendix is the problem.

I am now thinking I may have reversed the polarity of the motor causing it to spin in the wrong direction. This would be consistent with the motor spinning freely when engaged with the flywheel and the bendix doing its' job. I'm just not sure how I could have done that or what I could do to reverse it.

The parts I got aren't original BMW but fit the starter perfectly. They are, so far as I know, Marelli which is the original starter manufacturer.
I'm wondering if the brush assembly, even though it fits, could be intended for another starter meant to spin the other way.

Does any of this make any sense to anyone and does anybody have any clever ideas or thoughts for me?
 
Hi,

It doesn't make sense you seem to have covered everything I would have thought of, unless the flywheel ring gear is damaged and it has nothing to engage into(unlikely)

I suppose you can check your connections again , but I think it quite hard to cross connections on a starter motor !

Can you confirm by testing the starter (when removed) to see if it is turning in the correct direction ?

Good luck
 
Hi fixit man, and thank you for your response.

I agree that the problem is odd and I am more or less out of thoughts here.
I have the starter out and can easily check it's direction, however, I must admit that I'm not even sure which direction would be the right direction.
Do you, or anyone else, have an answer to that, clockwise or counter clockwise? (looking from the back of the motor)
 
Can't see at all how it would be possible to spin the wrong direction. The body of the starter is the earth, and there is only one wire to the unit which is the positive. Impossible to reverse.
 
I don't know which way...

The only way I can think of is to put the car in a forward gear 2nd or 3rd and move the car forward causing the engine to turn over slowly and see which way the flywheel moves.

You'll need some to help obviously (make sure the igniton is off) and it only needs to be a small amount, then you'll figure it out
 
fixit man said:
Check out this link :-

http://devongtrf.activeboard.com/t45974429/starter-motor-running-backwards/
Click to expand...

Good find, and a funny read if it's not you that wasted a day, could this be the answer? I'm sure we have all done something similar :oops:
 
fixit man said:
Check out this link :-

http://devongtrf.activeboard.com/t45974429/starter-motor-running-backwards/
Click to expand...

Turning the housing along with the field magnets the wrong way around?
It's a thought and I will have to check it to make sure, however, I'm fairly sure that with the way it's built it's impossible to reverse the housing and the magnets.
I will check it out though as I am completely stumped at this point and am willing to try just about anything. I will also try and push the car and feel the flywheel to get a sense for the direction it should be turning.
 
I checked the housing and the magnets and as I suspected there is no way to reassemble it the wrong way around.

To check the rotation of the flywheel I did the following:
The car was parked on a driveway with a slight angle rolling backwards.
I had my girlfriend sit at the wheel with her foot on the brake and the car in neutral.
Then once I had my hand on the flywheel I had her put the car in reverse and release the brake.
When the car, slowly, rolled backwards the gear engaged and the flywheel jerked, a very short distance, clockwise.

I repeated this twice. I am not correct in assuming that even though it was going backwards and it only ran for the short distance it took the gear to engage this would be the direction it would normally spin?

If this is the case and the flywheel should indeed turn clockwise then the starter should be running counter clockwise.
Currently it turns clockwise.

I am now pretty sure this is the fault as, when thinking about it, the bendix will allow the cog to freely spin counterclockwise but not clockwise.
Thus, if the axle spins the cog clockwise and it encounters resistance it will stop turning as the bendix will allow the cog to freely spin counterclock. while the axle spins clockwise inside it.

Have I confused you enough yet?

In any case, I still have no idea as to what I could have done to reverse the motor :P
 
ulfurk said:
I checked the housing and the magnets and as I suspected there is no way to reassemble it the wrong way around.

To check the rotation of the flywheel I did the following:
The car was parked on a driveway with a slight angle rolling backwards.
I had my girlfriend sit at the wheel with her foot on the brake and the car in neutral.
Then once I had my hand on the flywheel I had her put the car in reverse and release the brake.
When the car, slowly, rolled backwards the gear engaged and the flywheel jerked, a very short distance, clockwise.

I repeated this twice. I am not correct in assuming that even though it was going backwards and it only ran for the short distance it took the gear to engage this would be the direction it would normally spin?

If this is the case and the flywheel should indeed turn clockwise then the starter should be running counter clockwise.
Currently it turns clockwise.

I am now pretty sure this is the fault as, when thinking about it, the bendix will allow the cog to freely spin counterclockwise but not clockwise.
Thus, if the axle spins the cog clockwise and it encounters resistance it will stop turning as the bendix will allow the cog to freely spin counterclock. while the axle spins clockwise inside it.

Have I confused you enough yet?

In any case, I still have no idea as to what I could have done to reverse the motor :P
Click to expand...

Once again..yes sounds like you're bang on...the plot thickens !
Can you get another starter to try ? and take it back If you dont need it ?? :)
 
VICTORY! I finally figured it out.

Having all but assured myself that the polarity/rotation of the starter was the problem I decided to divide and conquer.
I disassembled the starter (yet again) and began testing the components individually. Having tried the motor by itself and even swapped in the old brushes for a brief test I still was no nearer. Then when assembling the starter again I noticed that the motor housing has a nib on it that slots into a notch on the backlid.
I had seen the nib and the notch before and just assumed (rightly) that these were for alignment. However, this final time I assembled the starter I noticed that there were two notches on the backlid. I tried aligning the housing with both notches and lo and behold depending on which I selected the motor turned in opposite directions.

So, apparently, the motor is designed to spin in either direction, selectable through the rotation of the motorhousing.

I just didn't know this, didn't notice the second notch and always assembled it using the same one causing it to turn in the wrong direction.

I'lll post a picture of the notches later tonight.

Thank you fixit man and all the others who chimed in in helping me to fix the problem.
Much appreciated! :D
 
Brilliant result, Yes it helps when you know for sure about direction etc., good lesson for any future DIY starter motor overhaulers

:D :thumbsup:
 
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