Main.TrailIndexPage | Electrical Systems | Starting motor

Starting Motor

This component is part of Electrical Systems.

Definition

Define the component. Include, if known, the german language word for the component, as well as the English or American equivalent. Show a picture, a diagram.

  • Its technical name & common name(s)
  • part # - start year & end year
  • which area it belongs to - engine, transmission, body, injection etc, link back to the relevant section

Function

Describe, in general terms the function of this component. Meaning what is it there for and what role it plays. Describe how it works, the inside mechanism. Use diagrams to explain.

Maintenance

Describe common maintenance procedures, and common faults that may occur. Describe how these may be diagnosed and resolved. Again, include diagrams, photographs and explanations. Where possible, include measures, tolerances, weights etc.

  • Symptoms when it faults
  • How to test if it is faulty - what tools to use
  • How to fix / change

Replacement Procedure:

The Removal and Replacement of the starter described here was performed on a later 250sl LHD, manual gearbox, power steering and no A/C. From what I understand, it may be a bit different on RHD and Automatics.

Depending on the year of your Pagoda, your original starter may be a .8 KW or 1.4KW. The SR59X is a 1.4KW and works in place of the original .8KW. For originality die-hards, you can always have your .8 KW unit rebuilt. However, the 1.4KW SR59X made an impressive difference in cranking.

Time: I think that a trained shop with a lift can do this Job in less than one hour. For those of us working on our backs with jacks and wheel chocks and taking it one thoughtful and safe step at a time, it can take about 3 hours.

Parts Needed:

Starter Bosch Rebuilt USA part number SR59X (it seems Europe may use a different part number: 0986010850) You should confirm prior to ordering. These numbers are as of January 2015.

Bolt, nut, washer & lock washers If your existing starter has two allen bolts and thread directly into the starter (both top and bottom bolts) than you will need to have one 10mm x 90mm bolt, washers and lock washers on hand for the bottom attachment. The new starter does not have threads on the bottom attachment and requires a bolt/nut/washers. Later pagodas may already have this bolt on their old starters.

Wire and connectors if you will add the wire to the coil to earlier cars that did not come with this feature -- optional.

Removal Procedure:

1. Disconnect the Battery!!

2. Make sure you disconnected the Battery.

3. Pull the carpet from the right side of the transmission tunnel, expose the oval panel on the side, and remove the panel.

4. With a light you will be able to see the allen head about 20cm inside the opening. You can feel it with your hand. Use your 10mm allen socket, wobble extension and ratchet and remove this bolt.

5. With the car safely jacked up and supported on the right side, you can reach the bottom bolt/allen head from underneath. Be careful and support the starter when you pull the bolt.

6. For me it was easiest to point the starter up so the electrical connections were facing down and I could undo them from under the car. Remember what goes where, or take photos.

7. You can now lower the starter out.

Installation Procedure

Reverse the removal procedure taking care to keep the wires away from the exhaust manifold.

Also use the new bolt/washer and lock washers on the lower attachment.

Old Yahoo content

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1971 280 SL ... trying to start the engine (cold or warm)...when the key is turned to the start position, I hear what sounds like a solenoid click and then a soft high pitched whine (the fuel pump) but the engine does not crank, the top red light (Alternator?) shows on the dash. If I turn the key off and on two or three times in fairly rapid succession, the engine starts normally, runs fine. This refusal to start is intermittent, in a day of six starts, maybe two or three need the extra turns of the key. Is this an ignition switch problem? Is there a safety interlock at work, or what?

Sounds like the solenoid is not throwing the starter gear out like it should. I have a similar problem. When I turn the key, it just clicks. I've cleaned all the electrical contacts including the interface between the starter and bell housing. Sometimes it works, sometimes it doesn't.

Joe Alexander says: the starter assemblies used on the 113 cars were .9 horsepower on the early cars and around 1970 changed to a 1.4 horse power. Most four and six cylinder Mercedes sedans of the era also used the same starters up at least into the late 70's. The later 1.4 horsepower starters can be used without any modifications in the earlier cars and give a noticeable increase in cranking speed and power. So find a nice sedan parts car and salvage a spare (1.4 PS) for a spare or upgrade. Always check the neutral safety switch on the starter circuit if your car suddenly developes starter problems.

I had a 230 SL 30 years ago with the identical symptoms. As best as I can remember: The whine of the fuel pump is heard when the key is in the first position. If this is what you hear, it is not the starter. In my case, the click of the solenoid was also accompanied with a noticible drop in voltage (head lights would get real dim). I came to the conclusion that I had a bad spot on the ring gear which would cause the starter bendix gear to get jammed. When it happened, I could get the engine to start by physically rotating the engine a couple of degrees (pulling on the fan belts, I was much younger then). Then the starter would work just fine. I later discovered that the problem was simply that my starter was loose (I was younger not smarter).

If your car is a 230 or 250 SL, it has a .8HP starter. The 280 SL's and most all six cylinder cars built in 1968 to 1973 have a 1.4HP starter. They are interchangeable and are marked on the case of the starter if they are .8 or 1.4. Makes a big difference.

I have started restoring a 1969 280 SL. I am having trouble removing the starter. I have succesfully removed the bottom nut holding the starter but have so far been unable to see how to remove the top bolt. Access appears to be from behind the transmission housing. Any ideas?

Dan Caron: there's a small plate that you remove under the passenger side carpet just above the floor to get at it. These are usually 10mm hex head screws so you will need a set of sockets for this purpose. If you don't have them, get them. You'll be needing them a lot.

Last Saturday, I turned the key and the starter motor did not engage. Ignition light came on, fuel pump was humming away but, but turning the key to its end position did not yield anything. First I thought I did not have the car in Neutral or Park (it's an automatic) but that was not the problem. I tried moving the gear selector, fondled the plug that attaches to the gear selector switch etc etc but no luck. Then, after about 10 minutes of doing nothing except cooling down, the car just started right up as if nothing had been the matter. The next day, this problem reocurred several times. So Monday night, I set to working on the starter motor for the first time ever, and this took all evening. First I wanted to remove the whole thing intact, but this to me seems impossible without first removing the whole engine (...).I finally replaced the solenoid unit that sits on top of the starter motor with a spare one I had lying around. Took the car for a test drive, and it "seems" ok. But I did lose confidence - should I also replace the starter motor itself? Is it likely it is just the solenoid? Does it sound like it could be the wiring, the ignition switch itself, some kind of starter relay? I am afraid of going on a trip now!

Sounds like your starter has developed what I call 'dead zones' where the magnets are perfectly aligned with each other and there is no direction to push it into. You might want to give the starter a tap with a long pipe or broomstick to jiggle the position. It seems impossible at first, but you can remove it from underneath. Jiggling the starter around the maze of steering linkages, mufflers and frame rails. Sometimes simply rotating it from one way to another while sliding it forward and also turn the wheels to the side to give more clearance when it comes out or is it straight? Been a while ago since I crawled under there.

I do have a similar problem with a '71 280SL Manual tranny. Once in a while at random times, I turn the key half way, the pump starts, red light comes on, then I turn the key the rest of the way...nothing... I've been told it's a loose wire, it's the solenoid, it's the ignition...etc...I have never looked deeply to see what the problem is... The solution that works for me when it doesn't crank, is to take the key completely out of the ignition and re-insert it, then when I turn the key, it starts immediately.

The two bolts that hold the starter to the bell housing of the engine are indeed removed from the rear of the car. A very short allen socket mated to a swivel and a long 3 foot extension and then the ratchet or breaker bar is what I recall from my days in the shop. This method also applies to the sedans and coupes as well. Or you could try the other unorthodox method-remove the transmission tunnel carpet and remove the round metal plate nearby under the heater box in front of the shifter lever and try from that access hole. But that one is a hit or miss and requires 2 people to guide the socket and ratchet to the bolt. The dignity of stranding your precious car behind in a parking lot overnight or on the side of the road easily overcomes the risk of opening the hood and banging around in the engine bay. This has happened to me on several occasions and no way would I leave the car behind.

What happens in my case is that, with the starter being so close to the exhaust manifold, the terminals (copper) heat up and expand. This repeated expansion and cooling causes the female connection point on the wire to work its way down the male connector such that eventually contact is not made. If I wait a few minutes it will cool down, the connection will become close enough to make the electrical connection and the car will start. The solution may be to change the connector end so that it is a screw on connector and not a spade connector.

Joe Alexander: If you have no history on the starter, then you may just want to remove it and take it to be reconditioned or exchanged. Then you will not have to worry about it for a long time. The most common problem is worn down brushes that don't quite make contact anymore. Jolt the starter by hitting it with something to get yourself going if you get stranded in the meantime. Assuming the wiring connections, the nuetral safety switch on the transmission, and the ignition swithch are good, proceed to the starter. It is a fairly easy removal with a few tools and some tips; First disconnect the battery so you do not short out something while working down there. Raise the car so work can be performed from below and above. Remove the starter wiring from below. Now for the top bolt, as Walter mentioned, access through the inside transmission tunnel cover plate (right side) makes the job much easier. Now using a 1/2" drive rachet handle, a 10mm allen stud, and the right length extension you can connect to the top bolt and remove it from inside the car. The lower starter bolt is removed from below. If you do not own a set of wobble extensions now is a good time to invest. These extensions hooked together will work like universals and are easier to control. Actually you can reach both the starter bolts from below with these extensions. You will be working the rachet handle from behind and below the transmission. These are the tools of choice for those upper transnsmission/engine bolts also. Turning the steering to one side will allow enough space for the starter to drop out the bottom. It is nice to have a spare starter rebuilt ahead of time so you have no downtime! Remember almost any Mercedes gasolene sedan starter 1969 through 1975 will work fine. Early 113 cars used a .9 P.S. (horse power) starter. Around 1968 an improved 1.4 P.S. (horse power) was used in all 113s and sedans. The improved units are stronger and will work in all early cars also. Your car should already have the 1.4 P.S. Once you've gone through the starter you should not have to worry about it for 60,000 to 100,000 miles. Now how about that alternator?

I have the problem as well. It is unpredictable, but most when the car is well at temperature. I jumpered from the battery + direct to the starter solenoid, and the car would start. Now, I have installed an emergency pushbutton, with switch in series under the dash, battery + onto the solenoid, with fuse in line. When it happens I leave the ignition key in contact position, I turn the switch and push the button, and the cars starts fine at all times.
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