couple of starting problems 85 300 SD
 

For one somtimes the bendix will not engage wondering if a good cleaning and oiling it would help? Another big problem is the NSS switch not letting engine start. Can the contacts in them wear and the only thing is to replace it? How does it come off as when I looked at it only seems like there is about an inch and a half of space to side of trans tunnel. An easier and cheaper thing to do might be to just jump the terminals on the block inside of car by gas pedal but that seems covered up by the carpet glued to plastic and a bear to get at that. Really, had a problem to get it started this morning in minus 4 temps. And might get colder tonight.

I'm not sure what the bendix is. Can you elaborate?

The best solution for the NSS is to just replace it. I had a problem with the one in my 300SD a few years ago. It was not overly difficult to replace. While it was dead I had to start the car by jumping the start at the dist. block near the air intake.

NSS part number 000 545 49 06, cost is about $65.

I think if you remove the carpet on the driver's side of the center console there will be a connector that has a number of wires in it, among them should be the NSS, speedometer signal, brake lights, reverse lights, etc.

bendix is the generic name for the gear on the starter.

you could have damaged teeth on either the starter or the flywheel... pull the starter and confirm.

http://www.peachparts.com/shopforum/diesel-discussion/293895-om617-starter-motor-life-not-just-christmas.html?highlight=starter+bits

Well, that is kinda broad...
it is actually the name of the mechanism which moves the gear on the starter into contact with the teeth of the flywheel on manual cars... the flexplate on autos.....
It is the mechanism on a spiral groove which allows the gear to engage and disengage once the engine starts.... is it not synchronized by design...thus contributes to the wear over time of both the gear teeth and the flywheel teeth.
In the OLD days..... many cars had starter/generators which DID NOT disengage... electricity applied to it turned the engine... then the engine turned it and made electricity....
so the invention of the Bendix was a major improvement in internal combustion engines...

correct.

but the poster was saying his bendix was not engaging... most use the term bendix to mean the starter gear...
in otherwords, he hit the starter, and it went "whirr" without spinning the motor.

Well, learn something new everyday..

Bendix drive - Wikipedia, the free encyclopedia

My tractor does that! Then I smack the starter with a hammer and it changes its mind.

I think you guys get the picture of my problem yes I am referring to the gear on the starter that is not engageing the flywheel. It is strange in that it never did this before I noticed that I was missing my top bolt of the starter a little while back when it would not start but think that was due to a lose ground strap any way ever since I did replace missing mounting bolt it started not engageing. I am thinking what might be the problem is that when the 1 bolt was missing the starter wore in the slightly cocked position it was and when I replaced bolt it put starter in a slightly straighter position and now I am having problems. I might try to loosen top mounting bolt to put in former position and see if problem stops or pull starter and closely examine , clean , and lube shaft that bendix goes in and out on to engage flywheel. On the NSS issue I think the junction box for the wires from it are somewhere behind carpet to the right of gas pedal I think that would be easier to get at rather then the switch itself. Thanks for all the replys I value them all.

This will not help that problem. The "starter drive" is most likely worn out. Its got friction material in there that engages the motor to the "bendix".

Best bet IMO is to find a shop that does rebuilds on starters,alternators and take your starter in for a rebuild.

From your link:

"...... For this reason the Bendix drive has been largely superseded in starter motor design by the pre-engagement system using a solenoid."

This new design is often incorrectly called a Bendix. The new Bosch design use a solenoid to actuate an "over running clutch".

Here's a good explanation of how it works Engine Starter Description

I second that. My 85sd had the starter dragging and when it got cold that was it, so I took it off went to a local shop that does rebuilds and not had a problem since. I am still amazed how much lighter it sounds when it starts up.

Don't fall for garbage at auto stupid unless you like scrapping your knuckles and and bending your back every 2 yrs:D
greazer2b

Lets throw in a few more possibilities for future reference... which can cause ' spinning ' but not turning the engine over...
First... teeth can break off the flywheel.... or the entire usually welded on ring of teeth..can become damaged... you can check this by rotating the crank and trying the starter again...
Second... teeth can be broken off the gear being brought forward to meet the flywheel teeth... this can cause a real jam and ruin the starter and the ring gear on the flywheel if it sticks ...
Third... gunk can cause the spiral to not bring the gear forward due to centrifugal force..
Fourth... a broken mechanism or gunk in the solenoid can impede contact.
I have mixed problems from both types of engagement mechanisms....