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Old September 10th, 2014, 14:37
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GrimmJeeper GrimmJeeper is offline
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[Tech writeup] How to rebuild your starter

The starter is a fairly simple part, with not much in the way of moving parts. Hopefully this write up will give you the confidence to at least tear your core apart and have a look in there before you turn it back in to the parts store.

First off, my problem. My jeep was cranking very slow, almost like the battery was dying. First thing I did was check the battery with a load tester from the auto parts store. it checked out fine, so next I checked the battery cables. I noticed some corrosion creeping under the insulation of the ground cable so I made up a 2g replacement with copper lugs on each end. Still having problems, i eventually ran into the problem where it wouldn't crank at all, just clicked when i turned the key. I had a buddy try to jump start me and even though the dash gauge read 14v, it still would not turn over. Remembering a trick my dad showed me, I tapped the starter body from underneath a few times and tried it, it fired right up. this means there is a dead spot somewhere inside the starter where the current is either shorting out or cannot pass because of some obstruction.

So, here we go. I bought a rebuilt starter to replace mine with, but I thought i would tear the old one down and rebuild it to show some of you at the very least something you havent seen before and may even want to attempt yourself. All the parts only fit together one way so there is literally no way to screw up putting this back together unless you forget to put something back in

Step 1) Remove the starter and get your tools ready.

For this job I used a 12mm socket, my trusty 3/8 ratchet, a blunted phillips screw driver (more on that later), an 8mm socket, a standard phillips screw driver, some medium grit sandpaper, brake cleaner (electrical cleaner would have been a better choice here but I am currently out of it), and a pair of gloves (latex shown but i switched to my mechanics gloves once the brake cleaner started eating away at the latex



Step 2) Clean the outside of the starter as well as you can

Dirt is the enemy of electronics and you don't want to do all this work just to accidentally smudge grease inside of it and ruin it while you're re-assembling it.



Step 3) Remove the energizing wire

This nut should take a 12mm socket. remove the nut, gently pull the wire off of the stud, and push it off to the side for now.



Step 4) Remove the solenoid

Remove the two large phillips head screws securing the solenoid to the main gear housing. this is where the blunted screwdriver comes into play. in the first pic you can see the sharply pointed tip of the phillips screwdriver. If you use this screwdriver you will strip the screw head out because not enough of the tip engages the slots in the screw head. the second pic shows (sorry for the blurry shot) another screwdriver i have ground the pointed tip off to make a flat end. this will let the driver tip sit all the way down into the screw head and you can torque down nice and hard on those screws to get them out. I had to put the starter in the vise and then use both hands to turn them out, the are seized in there pretty tight.

pic 1


pic2


With the screws out, you can now remove the solenoid from the gear housing. notice the spring inside the solenoid, DO NOT LOSE THIS. if it doesn't go back in your bendix gear will not retract away from the ring gear when you stop turning the key. that's bad



Now remove the plunger and set it aside.



Step 5) Remove the starter motor from the gear housing

These two long bolts hold the starter motor itself onto the gear housing. they take an 8mm socket and should spin out easily.



once they are out hold the starter so the nose is facing DOWN and gently slide the starter motor upwards and away from the housing. we do this so the planetary gears and the centering ball bearing don't fall out of the gear housing and get lost.

On the left side here you will see the planetary gears which provide gear reduction so the small starter motor can turn against the compression of the engine with ease. they simply slide on and off of the shafts they are on, should one fall off just pop it back on making sure the teeth line up with the outer gear ring. If you look closely into the hole in the center you can also see the ball bearing, if it falls out just drop it back in the hole.



Continued in next post...

Last edited by GrimmJeeper; September 10th, 2014 at 14:45.
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Old September 10th, 2014, 14:38
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GrimmJeeper GrimmJeeper is offline
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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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  #3  
Old September 10th, 2014, 15:14
WB9YZU WB9YZU is offline
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Re: [Tech writeup] How to rebuild your starter

Interesting tear down.

Thanks for Sharing

-Ron
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  #4  
Old September 10th, 2014, 16:18
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Re: [Tech writeup] How to rebuild your starter

nice writeup.
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Old September 10th, 2014, 16:25
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GrimmJeeper GrimmJeeper is offline
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Re: [Tech writeup] How to rebuild your starter

i forgot to mention, if you do a lot of water crossing or mudding, and your starter is submerged often, opening it up and cleaning it out and re-lubing it at least once a season will make it last virtually forever. 99% of failures are caused by internal shorts, due to some kind of debris that causes the brushes to energize more than one contact at once.
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Old September 10th, 2014, 21:15
kastein kastein is offline
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Re: [Tech writeup] How to rebuild your starter

Great writeup man, I am a nerd and haven't even dug into one this far yet. Mostly because I usually smack em too hard too and realize when they make really nasty noises instead of starting, so I go get my core refund

In the future I will definitely be more proactive about starter rebuilds. Any chance you have a source for a rebuild kit including bearings/brushes? I've replaced a solenoid before but that is it.
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Old September 10th, 2014, 22:07
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Re: [Tech writeup] How to rebuild your starter

no source on parts but when i tear down junked motors people leave here they go in the core pile, i never throw away anything i might be able to use to avoid a core charge lol. I'm currently out of starters but i usually have 2 or 3 of them on hand to pilfer parts from. MarkW mentioned in chat today that he might know a source but I didn't ask who or where.

If I can find my junk alternator out in the pile tomorrow I'll tear that down too and do another writeup, those are a bit more tricky

I know i have a few calipers out there, maybe i'll grab a seal kit and do one of those, that's simple and pretty useful.

Last edited by GrimmJeeper; September 10th, 2014 at 22:12.
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Old September 10th, 2014, 22:12
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Anak Anak is offline
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Re: [Tech writeup] How to rebuild your starter

Good stuff.

I meant to do a write up when I tore into my starter a few months back. Edit: Went looking for it. Here is the source for parts that I used: http://www.aspwholesale.com/index.ph...productId=5985 That link can get you to other, individual pieces, not just the full rebuild kit. For my starter the parts are found under "Mitsubishi" rather than "Jeep".

One thing I would point out is that replacing just the brushes is something which could be done fairly easily on the trail, and the parts you would need to carry do not take up much space at all. At least, this is the case for the Mitsubishi starter which is in my '96. This may not be the ideal fix, but it could be a simple solution to keep things moving until a better opportunity came along.

The complete brush assembly fits in a small box, about 3" square and less than 1" tall.



I think it is worth carrying. You can wear your brushes down the nubbins and not realize it until it is too late.

I highly recommend getting the complete assembly. There are two brushes which you can replace by themselves fairly easily, but the other two are resistance welded to the retainer. Unless you have the ability to weld copper wires to steel sheet metal you are going to be disappointed. (It is the two on the LH side which go through the grommet which are readily replaced, but the two on the right are another matter entirely.)



If you remove all four screws out of the back of the starter you can then pull the back cover off without messing with the solenoid or the front gears at all. In fact, if it were necessary I think this could be done without even removing the starter from the vehicle. I wouldn't make that my first choice method, but if I absolutely had to, I think I could do it.

The fun part it getting the brushes pushed back in their holders so you can slip the assembly back onto the end of the armature.

You have to go from this:



To this (Holding all four brushes back with just two fingers):



So that you can then end up with this:



Then you just clock the brush assembly so it will line up with the screw holes in the back cover. slip the cover on, reinstall all four screws and you have replaced your brushes.

Get back home and you can tear it down properly and clean up the contacts and what not as explained by the OP.

BTW, getting the solenoid screws loose is indeed an absolute pain. I have found that one of the hand held impact tools is a good answer. One of these:

Last edited by Anak; September 10th, 2014 at 22:21.
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Old September 10th, 2014, 22:32
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Re: [Tech writeup] How to rebuild your starter

excellent! thank you for the addition to the thread
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Old September 11th, 2014, 07:52
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Re: [Tech writeup] How to rebuild your starter

awesome. Thanks dood. I always though about doing this but trying to get the damn solenoid screws out always put an end to that
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Old September 11th, 2014, 10:36
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Re: [Tech writeup] How to rebuild your starter

I have forever been interested in rebuilding alternators and starters. This did indeed shed light on the subject and made me want to try a starter even more. Excellent work, man!
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Old September 22nd, 2014, 22:44
WB9YZU WB9YZU is offline
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Re: [Tech writeup] How to rebuild your starter

Quote:
Originally Posted by GrimmJeeper View Post
[B]
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.




Just a comment on the above paragraph as I'm converting this to a PDF...

Medium sandpaper may be a bit rough for this. What's recommended is either fine sandpaper or crocus cloth which won't leave as deep of groves.

Also the area indicated "contacts on the main coil" are not actually contacts. They are stacked plates though which the wires are wound and multiply the field generated by current flowing though the wire. in the 2nd photo you can see the individual plates. That said, clean is good

-Ron
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Old September 23rd, 2014, 09:16
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Re: [Tech writeup] How to rebuild your starter

Quote:
Originally Posted by GrimmJeeper View Post
no source on parts but when i tear down junked motors people leave here they go in the core pile, i never throw away anything i might be able to use to avoid a core charge lol. I'm currently out of starters but i usually have 2 or 3 of them on hand to pilfer parts from. MarkW mentioned in chat today that he might know a source but I didn't ask who or where.

If I can find my junk alternator out in the pile tomorrow I'll tear that down too and do another writeup, those are a bit more tricky

I know i have a few calipers out there, maybe i'll grab a seal kit and do one of those, that's simple and pretty useful.
I'd definitely be interested in seeing a alternator write up. especially if you are easily able to increase the amperage output...
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Old September 23rd, 2014, 09:46
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Re: [Tech writeup] How to rebuild your starter

Quote:
Originally Posted by scoobyxj View Post
I'd definitely be interested in seeing a alternator write up. especially if you are easily able to increase the amperage output...
unfortunately i doubt I can pull that one off, i believe the output has to do with the winding of the coil and that's beyond my skill level. changing out bearings and brushes however is relatively easy.

work has been killing me lately but I'll try and find time to tear open the core i keep on the shelf in case i need it.

Quote:
Originally Posted by WB9YZU View Post

Medium sandpaper may be a bit rough for this. What's recommended is either fine sandpaper or crocus cloth which won't leave as deep of groves.
i agree, my idea of medium is different than most people's i suppose, I am used to working with the finer grits for finish sanding so my medium might be someone else's idea of fine. good catch

Last edited by GrimmJeeper; September 23rd, 2014 at 09:49.
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Old September 24th, 2014, 16:29
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Re: [Tech writeup] How to rebuild your starter

It's been a while since rebuilding motors and starters, but remember cleaning out and scraping the grooves of the commutator with some sort of tool such as a screw driver, knife, hacksaw blade, etc.

Remember using emery cloth instead of sand paper.
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