Weird Starting Issue - Take a Listen! - PeachParts Mercedes-Benz Forum

mrsaxman99 · #1 11-20-2008, 11:58 AM

This is on my '83 300SD with 250k

Have a listen to this:
http://filebox.vt.edu/users/chhill4/engine%20starter%20issue.mp3

The engine turns over once or twice, and I swear it kicks on one or maybe two cylinders, but then it "hops" off the starter, and it spins free (all as you hear in the above mp3. Is this a bad Starter Bendix, or is it normal that the engine will kick once, and pull itself off the starter (leaving the starter to spin free)?

I checked everything involving the glow plugs - all are 0.6-0.8 ohms, and see about 10.35 volts. I had previously found one that was shot (infinite resistance), and I replaced just that one. If all GPs are within spec (ohms and voltage), is there absolutely no need to change them, or might they still not be glowing as hot as a fresh new set would glow?

I am having a lot of trouble starting (read: it won't start) below about 45*F. I went to plug in my block heater, but I measured infinite resistance across all three prongs. Where should I look to find the other end of the three prong plug, and the actual engine block heater?

Thanks in advance for all the help. You guys'/gals' experience comes as pure genius.

rrgrassi · #2 11-20-2008, 12:03 PM

Sounds like a failing bendix to me.

Flounder · #3 11-20-2008, 12:08 PM

I had the same problem..........it's a failing Bendix. I lived with it for a year like an idiot before finally replacing my starter a couple of months ago. It made a world of a difference. I can crank til the cows come home now.

mrsaxman99 · #4 11-20-2008, 12:21 PM

Thanks for the quick replies! Can anyone steer me in the right direction to locate the Bendix? Can it be replaced separately of the starter? I remember reading somewhere that the Bendix spring can just get a little stiff from thickening oil...is there any remedy to "loosen it up" or otherwise get the spring back to life?

Thanks again!

Flounder · #5 11-20-2008, 02:32 PM

Springs are heat treated a certain way. Once a spring has reached its fatigue life there's no way to "rejuvenate" it.

When my starter went I put a rebuilt in. It's possible to replace just the Bendix mechanism but I figured the gear was probably buggered up also.

I didn't realize how slowly my old starter was cranking either. With the new one I have much faster cranking speed, which is critical in the winter.

mrsaxman99 · #6 11-20-2008, 05:39 PM

Is the bendix internal to the starter?

dieselnutnj · #7 11-20-2008, 06:32 PM

I agree get yourself a Bosch Reman. Excellent starter for the money. You will have less headaches and god forbid another problem occurs some rainy snowy cold nite and leaves you stranded. New ones usually spin much faster then the older ones and get them diesels running faster.

Oracle12345 · #8 11-20-2008, 06:40 PM

bench test the starter Also check circuitry. you should be getting more than 10 volts at the glow plugs. I also would do a voltage drop test across the wire from the battery to the starter. Check your battery. make sure you are using the correct oil. Have heavier engine oil than whats recommended will make turning the engine over harder than it has to be.

By listening to your audio sample it either sounds like your dropping voltage to the glow plugs or the starter. Also have your battery tested.

If you dont know how to do a voltage drop test across a wire just ask.

kerry · #9 11-20-2008, 07:04 PM

Sounds like the bendix is kicking out shortly after it engages. Don't really know why but a new starter might fix it unless the problem has something to do with electricity delivery to the starter.

minimike1 · #10 11-20-2008, 07:46 PM

It appears that there's so many benz off the road, that you would have an easy time locating a used one from a car in a junk yard, or something rotting away in a neighbors driveway. Also ask on this board under parts wanted.
I've changed mine, you need a real long extension and a Ujoint along with the metric socket. don't remember the size bolts.

curtludwig · #11 11-20-2008, 09:17 PM

My 300TD did exactly the same thing back to the previous owner (a friend) years ago. A new starter cured it.

He'd taken it to the airport and when he returned the valet couldn't get the car to start. "Sir, is there some special technique to get your car to start?" He had to go out into the yard and spend forever to get it going. The lived with the stupid thing for weeks until it got cold and was almost impossible to start.

mrsaxman99 · #12 11-21-2008, 11:39 AM

Thanks for all the replies...I picked up a reman that I will hopefully be able to put in today (if my fingers don't freeze off). I've heard the starter replacement isn't as difficult in my car ('83 300sd) as it is in others...

SD Blue · #13 11-21-2008, 01:35 PM

Ditto, the starter reman and yes it is much easier on the W126. When you get the car raised, crank the wheels all the way to the left and there is just enough space to remove it without taking a bunch of stuff apart. (Mine went out just this past weekend, just before the GTG, and the task is still fresh in my memory.)

Also, from my experience, it is worthwhile just to change all of the glow plugs and be done with it. I know, many will say that they can be checked with a meter but the problem is checking across a cold glow plug doesn't really confirm their heating characteristics. A more sure way is to remove the plug and power it up while suspended in free air, maybe even checking it with an infrared thermometer. But by the time you do all of that, it is just as easy to go ahead and change them out. Especially if it has been a few years since the last replacement. I've never found that trying to save one or two was worth all of the headaches.

mrsaxman99 · #14 11-21-2008, 01:49 PM

Has anyone stumbled across a link/thread/site with pics showing how to remove the starter?

SD Blue · #15 11-21-2008, 02:15 PM

I personally don't recall pics but here are a few hints that may help:

Be sure to disconnect the positive battery terminal first.
Access is from below for the entire removal.
As stated earlier, once the car is raised, crank the wheels left.
Remove the main terminal nut (17mm) and the solenoid-ignition switch terminal (#2 phillips)
There is a bracket on the forward end of the starter. Remove the two bolts holding it to the block. (12mm IIRC)
Loosen, till the starter is free, the two large bolts (10mm hexdrive) from the bell housing side. (It's easier to line things up if you leave them sticking through the bell housing.)
The starter will just clear the tie rod if you previously cranked the wheels. And yes, it can be a little heavy so beware of smashed fingers!

Install the front bracket on the new starter and reverse the order of removal to complete the installation. Also, when reconnecting the main starter terminal, ensure there is sufficient clearance from the exhaust heat shield to prevent future shorting out.