My attempt to go to work this morning proved rather dramatic.
My wife turned the key and the starter motor sprang to life but the solenoid did not engage. After a second or so my wife removed the key, this failed to interest the starter motor at all so there was a subsequent mad dash to get back into the house, find a 13mm socket and disconnect the battery.
Looking at the circuit diagram for the truck, I am struck by the number of boxes that give no hint at the internal contents. My first though is that the ignition switch must be fubar but if that is the case I don't see why the solenoid didn't engage. There is a relay labelled, "thermotime switch" that is between the solenoid and the starter motor, but unless it is more magic that I would expect, I don't see why it wouldn't energize when the starter does.
The instrument lights behaved as I would expect when turning the key except for the starter problem.
Has anything like this happened to anyone else? Ideas?
".....the starter motor sprang to life but the solenoid did not engage...."
Not sure what you mean here, since the usual way for the starter motor to spin is for the solenoid to close contacts that send power to the starter motor.
It would take a very strange sort of short circuit for the starter to draw power directly through the switch and you'd smell wires burning FAST.
My guess is that the solenoid closed, but the bendix drive did not reach the flywheel. This could be caused by the pivot pin for the throw-out arm in the starter gettig out of place and the arm moving in an improper manner. If this were the case, it would also be likely that the solenoid would jam in the closed position, causing the starter to continue to run even though power from teh key was interrupted.
Pull the starter and inspect the solenoid, throwout arm, pivot, and bendix drive. Good time to refurbish the starter anyway, with winter aproaching and all.
Thanks, that makes sense and considering it would cost about half what I expect a new starter to cost to get it towed to the nearest mercedes guy, I'll be pulling it in about an hour or so.
I wasn't expecting to have my arm covered in grungy old oil when I pulled the starter.
Oh and by the way those two bolts are more of a bastard than I could have thought possible. I'm not looking forward to trying to put this thing back in. Don't bother attempting to pull the starter unless you have enough bits and pieces for your ratchet to make a decent rube goldberg device. I managed it in one trip, just, to buy a 10mm allen head socket. Also, as much as it seems a good idea, there doesn't seem to be any compelling reason to remove the heat shield from the starter first, except perhaps that it is a little easier to remove...
I'm thinking that the weep hole plug hasn't been removed in a long long time.
I had the same problem with my 280. The trouble with the 280 engine it has a weak crankshaft oil seal and when parked facing up a hill they tend to leak oil into bell housing. Look underneath at your starter motor at bottom of solenoid. There is a little split pin which allows water to escape. If you can see oil dripping from this then the oil has contaminted the starter. I always leave my bell houseing drain plug out to allow any oil to leave rather than it swishing around inside and getting inside stater. I had to remove starter and have it cleaned and new solenoid.
If you do go of roading replace drain bung as any water that gets in will damage auto gearbox seal. Beleive me i've been there
[V]
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look mummy, there's an aeroplane up in the sky (Is there anybody out there)
afetr replying I see you have already taken starter off and found the oil. You have a leaking main shaft oil seal. Try to leave oil between 1/2 and full on dipstick as if you overfill the oil pressure will blow oil out of seal. To replace oil seal you have to drop crankshaft. Don't bother as it will go again. Just leave the bell housing drain bung out and let the oil drip. Mine only leaks if its on a hill, or I have exceeded 80MPH or taken oil to full mark on dipstick. The w123 saloon 280 was also pron to weak oil seal. Maybe hipline can throw some light on the oil seal, he may have managed to replace oil seal in main shaft without taken out crankshaft?????
[}:)]Happy days.
I leave the bung out too. Keep a spare in the glove box for trips with potential wading. Mine leaks a bit, but not terribly. I haven't had any problem with starter contamination. I do need a new bendix drive before winter though. Mine slips when it's cold. Pulled it apart once to check solenoid operationand that was fine. Seems to be the bendix would rather live in TX with the vehicle's previous owner. Should I send it to you Erwin? [:)]
I haven't tried the bit about maintaining sump level a little low. That might help it leak less. Thanks Ian.
The starter went off to the local motor rewinder and I must say they did a wonderful job. It went out all rusty and scummy with a fairly worn spur gear and came back looking new. One part had to be brought from back east and it was still done in two days. Mind you it was still too hot to touch when it made it to my driveway so it was a full two days.
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