1982 w123 240D starter solenoid stuck on - PeachParts Mercedes-Benz Forum

atombaum · #1 05-23-2003, 07:40 PM

Had a strange thing happen four weeks ago and it happened again tonight. When attempting to start the car, the engine started but the solenoid stuck on and kept spinning fast. I disconnected the battery. Then it spun down. No problems after that. Is the starter strait forward to remove? I guess it needs to be rebuilt and the solenoid needs replacing. Does anyone know the cost of a new unit? The reason I ask about the ease of removal is my '66 w108 has a trap door on the transmission tunnel to gain access to the starter bolts. The diesel in question here has 298,000 miles. Thanks.

Motorhead · #2 05-23-2003, 08:24 PM

The 240 starters are pretty easy to remove. It takes a 10mm allen to get one of the starter bolts out. With that mileage... more than likely, it would be a good idea to replace the starter with a rebuilt unit. You CAN take the back cover off pretty easy and ck the brushes and if they are good, just lube up the bushings and replace the solenoid. To get the back cover off of the starter, remove two small screws that holds a small cover on the shaft of the starter. Take that cover off and remove the horseshoe clip that is on the end of the armature shaft. Then remove the two larger long screws that hold the larger back cover of the starter. You will be able to see the brushes then.

#3 05-23-2003, 08:31 PM

Yes they are easy to remove on the four cylinder, but don't expect the five to be so easy.

Before you run out and get a starter there are two things you need to know. First you need to be sure that the starter is the problem. It very well could be the voltage remaining on the solenoid not turning off when released which would leave the solenoid engaged.

Since it is intermittent there could be voltage on the line somehow even after turning off the switch. You could rig a temporary test light and put it where you could see it easily. This way if it sticks again, you could look at the light to ensure that there is no voltage on the solenoid.

Secondly I have been throug starters on 123 cars and I can tell you from experience that the starter you get at the auto parts will not last long. You need to find a Bosch remanufactured unit or even one from the dealer. It will be worth the extra money in the long run. Been there, done that in about 800,000 miles of 123 diesels.

leathermang · #4 05-23-2003, 09:07 PM

Well, Larry went for the electrical... so I will mention the physical... the possibility that a spring is broken or rusted... or that crud has gotten into the solenoid is a real possibility...
so you may not have to deal with the starter if you clean and inspect the solenoid....
This would not be a typical starter complaint... it would be a typical solenoid complaint...

Motorhead · #5 05-24-2003, 02:22 AM

I agree with Larry in that if you need a rebuilt starter, definately go with a Bosch rebuild. I believe that the 5cyl turbo starter fits the 240 and it is a higher HP rating. This can be a benefit on a cold morning as it will turn the engine over faster.
The only spring that I know of in the starter, aside from the brush springs, is internal in the solenoid.

atombaum · #6 05-24-2003, 06:27 AM

I am encouraged by the replies that it is not difficult to remove on the 240D 4 cyl. starter. I will probably remove it myself have it rebuilt locally (specialty shop for starters with only a walk-up counter) and get a Bosch solenoid to go with it. That is, if the solenoid is a separate unit.

The same local starter rebuild shop that rebuilt my w108 starter first sold me a non-Bosch solenoid to go with it. As soon as I got the new unit in the car (having fun with gaining access to those backward mounted bolts through the trans. tunnel) I had to remove it again because the after market solenoid was not always engaging. Extra $25 for the Bosch unit. So I learned my lesson (again) there. They covered the extra $25, by the way.

I will also investigate (price) a rebuilt unit through a dealer even though I think the main problem here is the solenoid. The starter just made it through a very long cold winter and always cranks just fine. I would not replace just the starter "or" the solenoid. They should be maintained as a pair. I am just stating that the current (good pun, eh?) problem is directly related with the solenoid.

There is definitely power at the solenoid when the key comes back to "run" position, or it would not keep spinning. What I don't know is what normally breaks that connection when the key goes back to the "run" position. Is it a switch or relay at the solenoid? Is that relay or switch actually part of the solenoid (or starter) or a separate part? Perhaps if it is a separate relay, only that may need replacement (for now). If there is a relay, where is it located?

trivia:
The car is driven every day so the frequency of this occurance is still quite rare because it last happened 4 weeks ago.

leathermang · #7 05-24-2003, 07:05 AM

"The only spring that I know of in the starter, aside from the brush springs, is
internal in the solenoid."---Motorhead
That is the one ... the solenoid is a magnetic switch which causes large contacts to come together by way of electromagnetic coils, activated by the current from the key being turned on... thus, if the spring is broken or the sliding surface is corroded, the steel piston does not retract from the contact ...and thus the starter continues to recieve electricity.... which seemed to fit the description of the complaint...

dabenz · #8 05-24-2003, 11:44 AM

atombaum,
It's the key switch that makes or breaks the juice at the solenoid (sounds like you know the difference between the starter and solenoid wires). "... there could be voltage on the line somehow" from Larry Bible is the operative phrase. If the solenoid wire stays hot and the key switch is not a fault, then it's probably something else like a transmission interlock, seatbelt interlock, or those goofy "you gotta push the brake pedal to start it" things. Best best is to check the key switch, then dig up the wiring diagram for the other items. All this assumes you have the key switch actuating the solenoid, and not the gorilla pull switch.

P.E.Haiges · #9 05-25-2003, 11:05 AM

Atombaum,

Were you thinking about replacing or rebuilding you starter before the on-running condition occurred? If not, why now? If the starter cranks the engine fast enough to start easily, there is nothing wrong with the starter. I will agree that while you have it out, check the brushes and replace if necessary.

The solonoid controlls the starter so that is what your problem is: the solonoid. Get that fixed or replaced and you problems will be gone and ~$200 will be in your pocket. If it ain't broke, don't fix it.

P E H

atombaum · #10 05-25-2003, 11:13 AM

P.E.Haiges,

I like the sound of that. That's what I believe too but thought it made sense to repair both while they are out of the car.

I got a price on rebuilding the starter and getting a new Bosch solenoid. It will cost $95 for everything so that's another reason why I thought it would make sense to reburbish the starter motor too.

P.E.Haiges · #11 05-25-2003, 02:32 PM

Atombaum,

That's a good price for a rebuild but I think you are only getting an overhaul. For that price, they can't do much more than clean up your starter and maybe put in new brushes and maybe a bearing or 2. However it might be worth it if you get a good warranty and you are getting a new solonoid.

A rebuilt to me would mean a new armature and maybe new field coils if needed, brushes ETC. I got a Delco starter rebuilt for my Case Diesel tractor. An independent electrical shop did it. He put in a new armature, field coils, brushes/holders, drive mechanism, solonoid et al. . He told me about the only thing good was the outside steel cylindrical case and end caps. Cost $165 but it spins that Case engine almost like it was running. I thought it was a lot at the time, but is was worth it. The starter was over 40 years old.

P E H

JimSmith · #12 05-25-2003, 02:51 PM

atombaum,

Try Fastlane, I have had great results using their Bosch remanufactured starters. Get the heavy duty one for the 300D TurboDiesel, as the starters on all the W123 models are interchangeable.

A local rebuild is very unlikely to be more than replacement of mechanical parts, as noted above. These starters see a much harder life than the average car starter, and they suffer from heat degradation of the wire insulation. Changing springs, solenoids and bearings will not address the copper windings, which, when they go, give wierd symptoms. Like not starting the car in hot weather.

Finally, if you have had your engine start and run at a normal idle speed at about 600 to 900 rpm with the starter engaged, then I think your starter has been overspeeded enough that you would be better off getting a genuine Bosch remanufactured unit. The rotor on these things has windings that are without doubt a little different than they were before the overspeeding event. You normally get under 150 rpm on the engine with the starter, and a few seconds or more at 4 to 6 times that is not a good experience.

Hope this helps, Jim

atombaum · #13 05-28-2003, 10:49 AM

I removed the starter last night. No surprises. Only the lower (rear facing 10mm hex head) bolt had to be accessed from under the car. Everything else including the starter came out from the top. I first tried to remove the starter from below, but there was not enough space. So, with the air filter housing removed and the cable bracket (part of the battery tray) which holds the battery and starter cables removed...AND...the heater hose (same vicinity) disconnected, the starter could be removed. Thanks for all the help and encouragement.