Greg Bender

http://www.thisoldtractor.com/gtbender

Starter and solenoid repair (Bosch)

I've been meaning to rebuild a couple starters and solenoids I've had for quite some time now. One functioned perfectly but needed cosmetic improvement. That is the starter you'll see pictured below. The solenoid on the other starter functioned fine, but the starter did not turn. Cleaning up the commutator solved that problem.

1. Always start with a spotless work area!
   
   

   

2. OK, that's much better :> Here is the crusty specimen. Time to get started.
   
   

   

3. First, remove the wire connecting the starter to the solenoid.
   
   

   

4. When you are reassembling, you can reference the terminals so you make sure you align the proper terminal on the solenoid.
   
   

   

5. Now remove the screws the secure the solenoid to the starter.
   
   

   

6. This is what they look like. The wetness is from PB Blaster...expect to soak these and use an impact driver (the kind with a hammer) to get them unstuck. Upon reassembly, be sure to use loctite on these screws. If you don't, you run the real risk of them loosening up and falling out.
   
   

   

7. Remove the solenoid from the starter. Note how the hole in the solenoid's arm fits around the lever.
   
   

   

8. Here is a close up picture of the solenoid arm and plunger. I screwed the screws back in a few threads so I wouldn't lose them.
   
   

   

9. This nut secures the bolt that acts as a pivot for the arm that engages and disengages the bendix with the ring gear. You should be able to move the arm back and forth and watch the bendix (starter gear) slide back and forth.
   
   

   

10. Remove the nut and bolt. You won't be able to withdraw the arm just yet.
    
    

    

11. Next, remove the screws that secure the small rear cover.
    
    

    

12. Pull it off and this is what you'll see.
    
    

    

13. Withdraw the "U" shaped retainer from its slot.
    
    

    

14. Withdraw the shimming washer.
    
    

    

15. I first thought this was just one washer. But while I was cleaning everything up, I found it was actually a stack of 3 washers stuck together: 1 thick and 2 thin.
    
    

    

16. Remove the rubber seal.
    
    

    

17. Now remove the big screws. PB Blaster is your friend.
    
    

    

18. With the big screws removed, you can pry off the big end cap. Just a twist with a small screw driver is all mine needed.
    
    

    

19. Wiggle it off. It only fits one way.
    
    

    

20. Here is what is inside.
    
    

    

21. Here are all the parts for the top in the order in which to reassemble them.
    
    

    

22. There are 4 brushes total. 2 are secured to the brush plate and need not be removed. The remaining 2 are soldered to the field coils and must be removed. Just pry the spring back and pull the brush out.
    
    

    

23. Here the brush is removed.
    
    

    

24. Now the brush holder just slides off...you can get a better view of 2 brushes that are attached to the field coils.
    
    

    

25. Here is a view of the brush holder from the underside. It doesn't matter how it goes back on as the connections are identical.
    
    

    

26. Now you can pull the main body off.
    
    

    

27. Here it is removed. It only goes back on one way...I didn't get a picture of it, but there is a relief for the little rubber piece that fits between the starter and solenoid.
    
    

    

28. Now you can withdraw the winding. It comes right out and may bring the engagement arm along with it.
    
    

    

29. Here is how the engagement arm is supposed to engage the bendix. It is reversible so don't worry about right side up or anything like that.
    
    

    

30. Here is that little rubber piece that fits between the starter and solenoid holes. Pluck it right out.
    
    

    

31. To remove the bendix, use a 13 mm 1/4" drive deep-well socket to drive the steel collar down off of the wire ring. Tap the socket with a hammer.
    
    

    

32. Now pry off the wire ring.
    
    

    

33. And here is the bendix. I pulled it off as an exercise to see if I could do it, but I wouldn't bother with it unless it was suspect. It is very difficult to get the steel collar back around the ring. I spent more time doing that than anything else. It finally work after a spent a lot of time bending the wire ring with a pliers to get it very close to the size of the recess. Doable but not fun.
    
    

    

34. And here are the 3 pieces.
    
    

    

35. The winding. No need to drive the shaft out...I'm not that curious! That is it for the starter...from here you can clean up the commutator (the part that the brushes run on) with some fine sandpaper. You can also replace the brushes with new ones. Just a bit of soldering will take care of that. I gave everything a bath in some degreaser and then used my wire wheel to clean up the nasty exterior bits.
    
    

    

36. Alright, onto the solenoid. Remove the 2 screws that secure the cap. They may be covered in some silicon glue that you'll have to dig out first.
    
    

    

37. Here are the screws.
    
    

    

38. Now heat up the connections with a soldering iron. Once the solder has liquefied, pull upward on the cap with your hand. Then do the other side. Move back and forth until the cap comes free.
    
    

    

39. Here is the cap as it was removed.
    
    

    

40. A look at the contacts inside the cap. Clean these up well. I like to use a tiny wire wheel on my Dremel tool. Then remove any residue with a cleaner (like rubbing alcohol or carb cleaner or such).
    
    

    

41. Here is how the cap goes back on. In the picture I'm holding it backwards...so don't get confused. The side that has two wires angling up to the other (LEFT side in the photo) goes to the terminal on the cap with the spade connector. You can see these two wires better in the photos above. Don't get this wrong or you'll have to swap it back around.
    
    

    

42. Carefully remove the first cardboard shim.
    
    

    

43. Carefully remove the second cardboard shim. Yes, I found two of these on mine. Combined thickness was 1.5 mm or 0.6 in. Be very careful with these and do not lose or destroy them. The thickness they provide is critical. If they are totally destroyed, replace them with shims of identical thickness.
    
    

    

44. As usual, assembly is the reverse of disassembly. Be sure to use anti-seize on all of the threads EXCEPT for the bolts that secure the solenoid to the starter body...use blue LOCTITE on those. Put some grease on the bushings and on the shaft where the bendix slides.
    
    Here is the finished starter and solenoid reassembled and painted. I painted the starter with black truck bed liner in a spray can (thanks to Mark Etheridge of Moto Guzzi Classics for that tip) and I primed and painted the solenoid body with gloss black paint. Stainless steel washers and nuts at the rear of the solenoid complete the project. All in all, I was able to rebuild two starters/solenoids in about four hours of time one humid Florida Saturday afternoon in August, 2006.
    
    

    

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