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Old September 10th, 2014, 14:38
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GrimmJeeper GrimmJeeper is offline
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Join Date: Jan 2007
Location: Gardena, CA
Posts: 25,183
Re: [Tech writeup] How to rebuild your starter

Step 6) Disassembling the starter motor

To separate the outer housing from the inner winding of the starter motor, hold the motor as shown in the picture and press down with your index finger pushing the armature down away from the housing. once you can see the main body of the armature grab it with your other hand and pull it down away from the outer housing. I do it this way to avoid damaging the field magnets that are inside of the outer housing. By grabbing the armature itself you also prevent it from pulling out of the commutator assembly in the back of the starter motor cap and damaging the surface of the brushes inside. (you'll see what i mean in a second).

Uh oh... looks like i hit the outside of the starter too hard when i was smacking it with the hammer to get it to turn over. normally I would have taken apart another junk starter I had laying around, and by bending the tabs above the magnet outward, i would then replace it with a good magnet from another starter. You'll see why I didn't bother in a few moments.

Here we see the armature assembly. you can see a dark line scored in the center, this is where the broken magnet was dragging across the surface of the armature coil. this would eventually have lead to a failure as the magnet ground down even further and metallic particles filled the voids between the contacts of the armature and caused an internal short. comparing this to the above pic you will see the large crack in the center of the magnet lines up perfectly with the line on the armature.

Now we're in the home stretch, only one more part to dissasemble, the commutator. Using your pointed tipped phillips screwdriver remove the two screws in the end cap of the starter motor. making sure to not tear the rubber grommet that holds the energizing wire into the end cap, slide the brush assembly and armature out of the end cap and set the cap aside. Normally the armature would have slid out of the brush assembly before the end cap was removed. You soon will see why mine did not.

See the blob of copper at the tip of my needle nose pliers? that is NOT supposed to be there, and is what was preventing my armature from freely sliding out of the brush assembly. I picked it off with the needle nose pliers and then saw what i did not want to see.

The commutator (the part of the armature assembly that fits into the brush assembly) has more than a few melted contacts. something (most likely metallic dust or some other conductive substance) has gotten into the assembly and caused a short like i was describing above. the blob of copper i picked off was part of these melted contacts.

From this point on, if your starter looks like this I would turn it in as a core and get a new or rebuilt one. I will continue with the writeup but this damage is unsalvageable unless you have other starters laying around to salvage parts from.

Next wrap your medium grit sand paper around the commutator and spin it by hand until the contacts are nice and shiney. afterwards do the same thing to the contacts on the main coil of the armature.

In this picture you can see that the brushes themselves have been melted as well. this is also an unsalvageable condition because it will cross contact and cause a short. the brush faces should be clean sharp edged rectangles. if yours are, just polish them up with the sandpaper wrapped around your finger and put it back together one piece at a time.

Make sure to lube the internals of the starter with quality dielectric grease ONLY. put a dab in the bushing on the inside of the end cap, and clean out the planetary gear assembly and put a few gobs of grease on the side of each of the gears, another one down into the hole with the ball bearing in it.

Now, once it is all back together, you can bench test your starter with a battery and a set of jumper cables. put the starter into a vise and crank it down nice and tight (NOT on the starter motor body, there's magnets in there remember?) attach the positive side of the cable to the large stud on the solenoid (NOT the one with the energizing wire on it) and attach the negative side to the gear housing (usually near one of the bolt holes works well. connect the battery. now, using a long screwdriver or a piece of jumper wire, make a connection from the small terminal where the small wire you disconnected while removing the starter from the jeep was attached, and tap the other end to the positive side of the jumper cable attached to the stud on the solenoid. if it spins fast and you can hear the solenoid slam the bendix gear outwards you did it right!

On mine, once I cleaned everything up and put it back together it worked fine, but with the melted armature and the cracked magnet it was a time bomb waiting to get me stranded somewhere so I went ahead and replaced it. Hopefully this will help someone save a few bucks, learn something, or just show you how things work. Worst case scenario you just turn it in as a core and get a new starter anyway.

thanks for reading!
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