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Old May 10th, 2014, 16:55
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8Mud 8Mud is offline
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Join Date: Sep 2003
Location: Central Germany
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Re: Anyone rebuild their 4.0 XJ starter?

It may have little or nothing to do with the solenoid. The solenoid has two functions, one is the main contacts for the motor itself and the other is to mechanically push the main drive gear into the tone ring or flywheel teeth. The solenoid and the Bendix work together to help the drive gear into the tone ring or flywheel teeth. If the starter doesn't spin up, the contacts in the solenoid may be making contact, but the motor brushes aren't making good contact, the motor won't spin up and work the Bendix. The whole process can stop right in the middle and you may not hear the typical click from the solenoid, which doesn't mean the solenoid is bad.

And oil covered starter may mean the brushes are oil coated, the oil seeps inside someway. Submerging the starter in muddy water can also coat the brushes, it dries and makes for iffy contact.

The brushes have a lifespan, it really depends on how many start cycles, over a period of years, the starter has as to how long the brushes last.. Dried mud, sand or whatever is also an abrasive.

That temperature dependency may be related to oil covered brushes. Oil gets thicker when cold, thinner when warm. It may be a combination of oil covered brushes and short almost worn out brushes.

Most guys opt to by a rebuilt starter with a full guarantee and just replace it (on the guarantee) when or if it screws up again. The brushes kit for the starter cost more than half of what a rebuild costs (typically), Not really cost effective to rebuild one anymore.

The low battery is also likely an issue, the lower voltage has more trouble burning through the oil covered brushes and/or forcing a contact (arch) between the brushes and the commutator (the commutator is what the brushes push against while it rotates). Battery poles and grounds are also a factor, if they aren't clean they pass less amperage and/or voltage.

GoJeep.com has a write up on disassemble, cleaning and reassembly, but his site is down right now.

You may want to do a search, somebody posted a site with a budget set of brushes and the mounting plate not long ago. The brushes are cheap, the mounting plate not so cheap and a necessary part of swapping the brushes out. You can do the brushes without swapping the mounting plate out, but it is a pain and reliability may be iffy.

I saw one solenoid that had a torn rubber seal, the piston in the solenoid was a ball of rust. Getting the solenoid apart can be rough, the screws tend to chemically bond to the body of the solenoid and can be a beatch to get out without screwing them up. I've replaced one (XJ) solenoid in 25 years, my guess is they don't wear out or fail very often.

Last edited by 8Mud; May 10th, 2014 at 16:59.
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