W126 Starter issues

[rektide]

My starter is well on the way out, and it needs to be replaced. It gets one to four good cranks, and then seems to lose power. In cold weather, its often not enough to start the engine. The speedometer will blip periodically, the tach rarely, and the engine never gets thrown over fast enough to start.

So, it needs to be replaced. This is a W126, a `87 300SDL. How difficult is this operation? What does it entail?

A 30 second "feel what the starter is mounted in to" inspection in biting 10°F cold revealed two bolts holding the start on. With regards to the starter, is it just a matter of unbolting it and bolting in the new one, and changing leads? How much work is required to access the starter? From the top, I can see and feel the starter pretty well, but I'd wager those bolts will be torqued to >75lbs, which mandates better access. I havent yet jacked the car up to check underside access-- it looks like there may be some steering elements in the vicinity. How much equipment needs to be disconnected & moved out of the way, or is it possible to do this operation in place?

An older post seems to confirm this operation is relatively simple;

Originally Posted by amosfella

SDL starter is really easy to change. Take off the pans, undo the leads either from the top or bottom. Then jack up the front driver's side, and undo the two bolts. It takes a bit of maneuvering to get it out, but it's ok. Should take 30 minutes to do.

What are the pans? Seems like the maneuvering wont require disconnecting any steering/ other systems?


My one other concern is with finding a replacement starter. Currently my starter just doesnt have enough power to throw the engine over-- I want absolute certainty the replacement will have plenty of power, at least as much as a stock one. I presume a decent remanu'd Bosch will suffice? Are there any better options?

Thanks!
rektide

[rektide]

ohhh ffff; om603 starter motor replacement. thanks ccooper, somehow my initial search didnt find that thread.

[jim16671836]

Access the starter from the bottom when you have the car jacked up in a safe manner... You can access the wires from under the car and also by removing the Air Cleaner on a diesel. Be sure and disconnect the battery... From under the car you will need to remove two(2) allen bolts that hold the starter in place... use either a 8mm or 10mm allen socket.. Torque will not be to bad.. I usually use a short pipe over the rachet to help.. Some of the starters have a small bracket at the front of the starter but I think they are rare..

If you need a used starter in good condition for a 126 just let me know your location and I will give you a good price.. Jim

[kerry]

Why the starter and not the battery?

[rektide]

Even while jumping, the starter is massively underperformant... its 20F out now and I havent been able to get the starter to get the tach to move. The starter audibly sounds like its a lame.

[rektide]

I ought mention I'm at 9k feet elevation... that obviously has to have some impact on attaining sufficient compression to start up.

[compress ignite]

http://www.gbcnet.com/mercedes/docs/OM603%20Starter%20Motor%20Removal%20and%20Installation.pdf

[Brian Carlton]

Originally Posted by rektide

Even while jumping, the starter is massively underperformant... its 20F out now and I havent been able to get the starter to get the tach to move. The starter audibly sounds like its a lame.

It's not possible to jump start a diesel unless you've got some very expensive and heavy jumper cables. Even those cables are marginal due to the insufficient contact area of the clamps. Therefore, any judgment made on the performance of the starter based upon the use of jumper cables is, by definition, erroneous.

Replace the battery, thoroughly clean the cable clamps, and your starting problem will disappear.

[4x4_Welder]

I just (about ten minutes ago) yanked the starter out of my 82 with an OM617. Assuming they kept the same basic style, there are the two allen head bolts that you access from the rear, 10mm allen. There is also a bracket at the other end of the starter with two bolts. One thing to check is the cables, especially at the ends. These get corroded and add an enormous amount of resistance. Charge the battery and have someone crank it while you measure the voltage drop from the battery post to the starter post, if it's more than about .3v, there is excessive resistance and you need to replace the cable.

[compress ignite]

Armature

[Brian Carlton]

Originally Posted by 4x4_Welder

I just (about ten minutes ago) yanked the starter out of my 82 with an OM617. Assuming they kept the same basic style, there are the two allen head bolts that you access from the rear, 10mm allen. There is also a bracket at the other end of the starter with two bolts. One thing to check is the cables, especially at the ends. These get corroded and add an enormous amount of resistance. Charge the battery and have someone crank it while you measure the voltage drop from the battery post to the starter post, if it's more than about .3v, there is excessive resistance and you need to replace the cable.

None of the aforementioned techniques and procedures are applicable to the OM603. It would be beneficial to read the OP and ascertain the engine type prior to posting.

[kerry]

Originally Posted by Brian Carlton

Altitude has no impact, whatsoever, in the ability of a diesel to start. The compression is the same whether at 9000 feet or at sea level. However, the amount of air in the cylinder is reduced. The reduction in air has no affect on the start.

Hmmmm?? Compression PSI the same irregardless of altitude? I'm not convinced. Ratio yes, actual pressure, I think is less.

[4x4_Welder]

Originally Posted by Brian Carlton

None of the aforementioned techniques and procedures are applicable to the OM603. It would be beneficial to read the OP and ascertain the engine type prior to posting.

I went and read the .pdf link- Everything is the same as what I posted except the rear bracket. Just trying to help and contribute rather than be a leach.
The comrpession pressure will vary based on altitude, but it's not enough to worry about. Maybe 320psi vs 317-318psi. Not a factor. Cold, thick 15w40 isn't helping, poorly functioning glow plugs aren't helping, and having only about 30% of your full summer cranking power doesn't help either.

[Brian Carlton]

Originally Posted by kerry

Hmmmm?? Compression PSI the same irregardless of altitude? I'm not convinced. Ratio yes, actual pressure, I think is less.

Yes, that's got to be right. Compresssion is the same but the atmospheric pressure at 9000 ft will probably be about 13 psi. Therefore the final compression numbers must be less..........on the order of 260 psi with 20:1 compression.

This will impact starting capability.

Thanks for the clarification.

I'll delete the aforementioned post to avoid any confusion.

[Brian Carlton]

Originally Posted by 4x4_Welder

I went and read the .pdf link- Everything is the same as what I posted except the rear bracket. Just trying to help and contribute rather than be a leach.
The comrpession pressure will vary based on altitude, but it's not enough to worry about. Maybe 320psi vs 317-318psi. Not a factor. Cold, thick 15w40 isn't helping, poorly functioning glow plugs aren't helping, and having only about 30% of your full summer cranking power doesn't help either.

NP........just contribute what you've already done personally. If all folks would restrict themselves to this, we wouldn't send others on a wild goose chase for a bracket that isn't there. I'm sure you wouldn't want to be in that situation.