Project M54 Engine: Starter Motor

Starter Motor

Links to other parts of the project
http://forum.e46fanatics.com/showthread.php?t=899347

If you have a starter motor that's not working, this may help with diagnosing what the problem is. It may allow you to replace a component rather than buying an entire starter. The starter is made by Bosch, so I expect that it's a generic item that is in lots of cars, and getting hold of an individual component at your local auto electrician would not be difficult.

A couple of things before I start.
When I opened up this starter, it was obvious that the internal workings are semi open to the elements. To avoid premature failure, pulling the thing apart, cleaning it, re-greasing, etc would be a good idea in my opinion. There were lots of small bearings and gears that were pretty clogged up with gunk.
Also, I've never done it on my car, but from what I've heard, removing the starter is a PITA. It's under the intake manifold in a position that's difficult to get to. I've seen threads posted on how to remove it. However, once it's out, it's a pretty simple job to pull it apart and work out what's wrong with it.

Please excuse that state of this starter in the photos. The guys who I bought the engine from used brute force rather than unbolting the starter when separating the engine and transmission. The contacts on the solenoid have been broken apart.

Here are a couple of photos that show where the starter motor is mounted.





When out of the car this is what it looks like from the front and rear.





How it works (see photo below): When you turn the key, power goes to the solenoid. A solenoid is basically an electro magnet. When power is applied, the iron plunger gets sucked into the solenoid body (It's spring loaded to keep it out when there's no power applied)

When the plunger gets sucked in, it does two things.
1.It forces the gear on the motor forward to engage the flywheel
2. It makes a contact in the back of the solenoid, which allows power to flow to the motor and make it turn.
Basically if the gears are not forward and engaged with the flywheel, no power can be sent to the motor for it to turn.



Pulling it apart

Firstly remove the solenoid and plunger. There's a spring between the solenoid and plunger. Disconnect the contact that allows current to flow from the solenoid to the starter.



Once the solenoid has been removed, you can test each part to see if one is not working (if required)

The way I did it was I got some jump start leads and connected them to the battery of my car. I then connected the ends to what I wanted to test to see if it worked.

Testing solenoid: put the spring and plunger in the solenoid, and then connect the jump leads as per the photo. When power is applied, then plunger should instantly jump into the solenoid body.



Testing the motor: Connect the flappy lead that comes off the motor body to the positive lead. Now touch the negative lead to the aluminium housing at the front of the motor. The motor should jump to life. Don't worry, it's not dangerous. It actually doesn't spin that quickly.

To pull apart the motor section, here are some photos and instructions that will help. Initially remove the two long bolts as shown in the photo above.

Also, these photos were taken after I pulled it apart and cleaned it up. There was loads of filth inside.

Nice writeup!

great writeup

How do you know if i need to do this? reason i ask is sometimes when i start the car, the motor will turn over once, pause for a second, and then starts.