FRporscheman

This problem just developed overnight, so to speak. I park the '93 one day, then I come back a week later and it won't turn over. I assumed the battery was dead so I charged it, still nothing. All I hear is a loud click (solenoid) but no spinning or cranking. I tried a good battery from my '95 and still nothing. Jumper cables - nothing.

I took out the starter to try bench testing it. Except I don't know how to bench test a starter. I tried a few different methods of connecting wires and some gave me a spark shower... I can get the solenoid to activate but nothing from the motor.

I also have a known-good starter here I'm trying to compare against. No, this starter won't bolt into the 968 so I can't just slap it in and try.

FRporscheman

I answered my own questions. To bench test the starter, I used a spare battery and harness, I connected the +12v to the large terminal on the starter, and used a thick jumper wire to jump the +12v to the small terminal on the starter. Then I just hit the ground cable to the body of the starter - there will be sparks every time the starter is grounded, but it's OK.

I tried searching and I didn't find anything on how to bench test a starter but I did find info on how the starter is wired. A lot of bad info too! Just for reference, the exposed cable that connects the motor housing to the solenoid is a ground!

Thanks to being able to bench test the starter, I determined that the starter solenoid works perfectly, but the motor is really sticky. Sometimes nothing would spin. Sometimes it would spin v e r y s l o w l y....... And sometimes it would spin nice and quick. I don't know what the heck is going on. I opened it up and found some indications of wear. There were 3 rectangular bushing things around the bendix that are almost disintegrated and the white plastic bendix surround is broken in one spot. I bought this starter used to get me going. I guess I can buy another used starter but I'm leaning towards getting this one rebuilt to avoid any more issues.

Calmchaos

The guy at napa tested mine with a battery and jumper cables. One cable to the live and the other he just clamped to the housing and it spun it right up.

marky522

You arent looking for actual signs of wear causing the binding, what is causing the starter to spin slowly is when it is energized to sping instead of creating the magnetic field it is shorting directly to the center.

Mark

jpk

Whoa Nellie!!! I hate to say this, but you've just added to the bad info there... The exposed wire is the hot feed to the starter motor. It is NOT a ground.

The solenoid part of the starter does two things:

1) It has a linear actuator (linear motor) that throws the starter gear out to engage the flywheel. This is actuated by a plunger that pulls back into the solenoid housing forces the starter gear out through a fork lever.
2) It has an electrical contact that switches 12 volts to the motor. This switching has to handle upwards of 300 amps. The contact is actually at the base of the plunger rod that gets pulled in by the linear actuator.

The small wire terminal on the solenoid powers the coil of the linear actuator. The big wire terminal (from the battery and alternator) is the 12v+ feed for the motor. When the solenoid is energized, the plunger inside gets pulled in, which forces the starter gear out, and closes the contact between the two big wire terminals on the solenoid. Power then flows from the battery connection, through the contacts inside, and out through the bare wire to the motor itself and makes it spin.

If you measure resistance between the bare wire and ground you should read something. I don't know off hand what the spec is, but there should be some resistance through the windings of the motor to ground. It may only be a few ohms, which, if your meter is on the wrong setting could look like continuity.

If you want to bench test the starter, hook the negative clamp to the starter housing, and the positive to the battery connection on the solenoid. Jump across from the battery connection to the small wire connection on the solenoid using a screwdriver or something similar. You'd probably want to have the thing secured in a vise while you do this. Remember that the starter is rated at 2.5Kw, so your cables need to be capable of carrying around 200 amps - 10 guage wire won't do.

Jay W

I just had 2 starters apart this weekend making one good one. Both of them had a small piece of the white plastic part broken off right where the two long bolts come down through the housing to hold the motor on. When I put them back together I just positioned the broken plastic in its place and slid the motor on. Whether this will work in the long run I dont know but I didnt want to weaken the rest of it by leaving a chunk of plastic out, and it didnt look like it could go anywhere anyway. Secondly I noticed on one of them that where the starter gear spins around the shaft, it was really worn and loose around that shaft, likely causing it to bind up slightly. The other one was good so I used that front half section with the good motor. Check the starter gear for wear.

Pcar944

Ouch.

I'm no expert but on three occasions I've left my '86 sitting for more than three months and each time the starter needs to be helped back to life.

They "stick" so a few taps with a hammer can free them and you'll be good to go.

Pcar944

I'm willing to bet if you put the thing back in right now it'll work okay given the shaking its probably got from being removed.

Tiger03447

If you check the field coils in the case of the starter, look for cloth hanging down from them when you pull the armature out..Also look for polishing on the armature laminations (should be big smooth part) on the armature..if that is the case, the bushings in the starter nose and the rear plate on the starter have worn, allowing the armature to drag the field coils..with enough of this going on, it will eventually short out and you won't get anything from the starter at all. The tolerances are pretty tight in between the armature and the field coil..so it doesn't take much..this is the typical way a starter fails. You go and drive someplace, shut it off, come back out and nothing...maybe a click of the solenoid, but that's all. Check out an Advance Autoparts or an AutoZone for a rebuilt one with a lifetime warranty...or take it to an automotive electrical rebuilder..(scarce these days for an independent)..This is a Bosch starter and there are plenty of them out there..so price should be pretty low...good luck!

FRporscheman

Good info.

But I bought a Bosch rebuilt starter about 6 years ago. Still works great.