W126 starter not engaging
 

Pretty sure my solenoid or starter went south. But thought I would ask a little on how they work first.

Newer battery shows 12.4volts in sub-freezing temps. When I turn the key I hear the starter gear popping out and what *might* be the starter motor spinning. Start was always very quiet but it not the fuel pump I am hearing. Either that or I am just hearing the solenoid click and the gear staying in place.

Either way, when I try to start her that is all I get. All lights stay on, etc. I even fired up the rear defrost, heated seats, stereo system, lights, etc and everything stayed on - no indication of the car thinking the power level was too weak via flashing indicators on the various switches.

The alternator was replaced at same time as battery with new regulator.

So will the car even try to crank if power is really low or is there some minimum voltage, etc?

I did check the positive small red wire. I did wiggle shift, but that would only make the clicking happen a lot.

Sounds like a failed or sticking bendix. One of the ways a starter can fail. Solenoid, motor brushes, bearings, bendix. Thats about all there is to them....

When the starter fires up the gear pops out to engage the flywheel, if its moving too slowly or not going out far enough it will miss the teeth and spin freely or scratch.

Update: Had a friend help me out. Turned engine manually and its all free and such. No missing gear teeth on the flywheel.

The bendix gear is popping out just fine from what I can tell. But the starter motor is not spinning as I thought, just the loud fuel pumps.

So it would appear that the starter motor is not energizing right. If the bendix engages out, would the starter itself fire up or is that another circuit?

When I was doing the shifter wiggle test, it would engage in neutral. It no longer does, only in Park now. Does the switch provide separate power to separate circuits to start? My next thought it to replace it, only because it will not engage the bendix gear in any position other than park now. And maybe that is causing the issue?

Oh, I will be trying to power the starter on its own when I have time. Is there a way to do so form the comfort of the engine bay or will I have to get underneath?

If the '91 W126's have the 3 wire terminal blocks on the right passenger wheel well you can jump it there.

Jumped starter at ignition switch terminal. Clearly the bendix gear is engaging. Solenoid or starter motor must be bad. Thinking solenoid.

So I read about the horrible upper bolt. Mine was mostly out! Nothing appears cracked/damaged. Just not threaded all the way. Starter sure appears to be factory. The lower bolt is BAD though. Based on what people say, i dont think the upper is hard to remove. I think removing either one causes the other to stick a lot more. Either way, I am going to drop the exhaust to get these buggers out. Already destroyed my good u-joint and did some damage to some skin! Figure I will just drop the exhaust and speed this up. Then i can clean/bench test all day long!

By the way, with one bolt out as it was the starter was still dead firm. I could not move it at all. I dont think the loose bolt was the cause of the issue. But when out, maybe I will find something new.

take a screw driver will ignition switch on run.Then place screw driver on both connections if engine starts its you ignition switch
PS neutral safety switch can prevent starting too

The bendix and motor are triggered by the solenoid. So the motor probably has a dead spot in it or the brushes are worn down.

sounds like an open pole on the commutator of the starter, Best take it out

We have a big snow storm on its way, so I will probably drop the exhaust on Sunday and pull it out. Even if there is a slim chance of being the neutral switch, I want to pull and refresh the starter anyway. But since the bendix gear is coming out just fine, pretty sure the solenoid is at fault.

Found the problem!

Nothing. At least not mechanical. Got the starter out by dropping the exhaust. Since my exhaust bolts were new, this was easy. But I HIGHLY recommend it! Anyway, instead of taking the solenoid apart, etc. I took it to an Autozone for testing. Several tests and each passed and it sounded very healthy. Even the tech said it sounded great.

So after some lubrication I reinstall and all is well. My only though it some sort of bad connection. They all looked good, but that was the only change - that I cleaned them up nice. The only other change was getting that up bolt secured that was loose. But it was SO loose I doubt it was the issue or I would have had problems much sooner.

Either way, it starts very nicely again and I am happy to be motoring around in the Benz again. Now off to get that V12 running!