Hi,
I've got a 1987 300SDL that won't start.. The starter cranks strongly but it just won't turn over. It had been sitting for about a week and before then I'd started and run it daily with no drama. However, I have had to do the following in the last 2-3 months:

* replaced oil pan (crack drained about 2-3q per day for about 3 days)
* replaced cracked fuel lines, head gasket (caused by pulling the engine for the oil pan swap)
* replaced ancient glow plug relay strip fuse (it bent like lead in my fingers)
* standard oil change

All work was done at a Mercedes dealer (Mercedes of Wilmington, DE) except for the fuse. They mentioned that the vacuum pump was leaking oil (?) after the fuel lines were replaced, but I didn't have the time or money to have it replaced at that time (it was my only vehicle and I was commuting to Wilmington from Staten Island).

However, recently the car has been both shifting very hard and feeling very underpowered (going from 40-60mph taking like 15secs), and it's been holding gear longer than usual. Also, the hose near the head's oil cap had snapped loose at some point (it looked to be attached with some black/gray paste), but the car continued running, and I cleaned off the plastic connectors and put the hose in place and put some gel glue on top of the connector.

I'd like to get it running again, but I'm not sure where to start checking... Or how. Alternately if anyone could recommend a good independent shop within tow distance to Wilmington, DE that isn't booked 3 weeks in advance I'd be mighty appreciative.

TIA,
- Matt

i dont know the 87 model engine.. im guessing its an 6 cyl diesel.. but maybe they broke some vacuum line that goes to the tranny.. and your not turning over issue could be a drained battery bad terminal connections or a blown fuse.

Loosen an injector line at injector to see if you are getting fuel when cranking. Also better get a reading from your glow plugs to make sure they are really active when indicated. These two simple tests should give you some ideal of whats going on. I have to assume when you say the starter cranks strongly that the front engine pulleys are turning at the same time the starter is cranking.

That's correct.

I can check those things when I get home tonight, particularly the glow plug resistance (since I had to change the fuse in the relay).. I'm just wondering what would be affected by letting the car sit for a week..

You need to spend some time searching this forum so that you know enough about the car to talk to folks that work on it. All that work done at the dealer and their explanation of it sounds bogus to me. Was that a head gasket they changed or a manifold gasket? I ask that because I don't know how pulling the motor out of the car would mess up a head gasket. If it was a head gasket did they pressure test the head? Do a search on cracked 603 heads and see if you have any of the symptoms like oil in the coolant or a hard hose after startup.

If the starter is strong and the motor won't turn over maybe you have a hydraulic lock in one of the cylinders. To rule that out see if you can turn it over by hand.

If the motor cranks over and will not start you either have no fuel or a fuel leak that has caused air to get into the injection lines. loosen an injector line like Barry says and see if you are getting fuel. If you are getting fuel then tighten all of the connections and purge out the air. An SDL does not have a hand primer pump so you will have to crank it a lot to purge air from the fuel lines.

__________________
Tom Hughes
St. Louis
84 300SD
92 300D
86 300SDL

Matt,

Turns over and cranks are synonymous. I prefer cranks. What U mean is that the engine doesn't fire or start.

In a Diesel engine, the are 5 reasons for this: 1. engine is too cold, 2. heating device in engine (GP) is not working, 3. compresion is not high enough, 4. fuel not getting injected 5. timing is incorrect.

Actually there are are more possiblilties such as broken internal arts but the above 5 are the most common and should be investigated first.

One question that bother's me is how the head gasket was damaged by R&R the engine?

P E H

Thanks for the help so far, I've tested the resistance of the glow plug relay connector and all come up OK (0.1-0.2). I'll check the fuel delivery later on today, after I change the oil and plugs on the bike.

The old girl's up to 399k, I'd love to get her over the 400k hump, so I appreciate all the help and advice.

Cheers,
- Matt

Provided you see fuel out of the injector line, then check the following:
When you switch the ign ON is 12 volts applied at the glow plugs? Check any one of them. A test light is one way or a volt meter will do. Check from the tip of a GP to ground (chassis).
If you have 12V and fuel then I would suspect something that many will find odd but in fact has been known to cause diesels to not start.

I had a case where a 603 engine would not start. It had fuel, 12V at the GP's everything OK. It turned out the Trap Oxidizer (I should say NASTY Trap Oxidizer!) was plugged up. I mean completely plugged!
I was able to swap one from a wrecked car onto the engine to get it running again.
Then I immediately booked a recall operation (they call it Open Campaign) at the nearest dealer. The car came back running like a top! When the exhaust is plugged the 603 engine won't even start. Even a seasoned MB Indy mechanic couldn't believe it! Until he removed the exhuast pressure port at the front of the manifold and cranked the car, it started barely, just able to breath out thru that 3/4 in hole!

Does your car have the football shaped Trap at the exhaust or the later Cat oxidizer located under car, under the Rt front seat? They also have been known to plug up and cause a car to run extremely poorly.

RE: Vac Pump. Does your vac pump have a cover held on with four Torx head bolts? If not then its the original one and should be changed as soon as you can, the old pumps have destroyed many of these engines when they go to pieces and the bits get jammed up in the timing chain, oil pump etc. There should have been a recall on those too!
Also there have been instances where the turbo locked up and the car would hardly start and not run at all.
Let us know what you find!

__________________
'95 E320 Wagon my favorite road car. '99 E300D wolf in sheeps body, '87 300D Sportline suspension, '79 300TD w/ 617.952 engine at 367,750 and counting!

Mat,

I would like to know how you tested the resistance of the GP relay connector.

P E H

Hi,
As it turns out, I had it towed to a local mechanic, and luckily I found an honest one. Both the fuel filters needed replacing, and that got it started, but while it was there I had him look at the vacuum pump and change out the front end suspension and timing chain (I'm thinking the front-end was low and something hit the oil pan, so that won't happen again). The car's now up to about 401.2k mi.

He also pointed out a broken right-angle hose to the switchover valve, which had been the cause of very low power for like 6 months (couldn't go above 45-50mph uphill, 0-60 in like 35-45 secs). I was able to replace it with some hose and now the turbo kicks in like it should!

I'm hoping to push this car well past 500k mi, so far so good! Thanks everybody!

Mat,

Its unlikely that both fuel filters needed replacement. They are in series so if one filter plugs enough that the engine won't run, no more fuel will pass thru the other filter so it can't plug.

Anyway, does the engine have to be completely removed to change the oil pan. I might have this repair in the future which I will do myself. If engine has to be removed, this is a very poor design. Shame on the MB engineers for designing a car this way. If I was the lead engineer, it would never have passed my approval.

I worked for IBM when most of their momey was made from renting data processing machines. Since IBM was responsible for the maintanance cost on the rental machines , servicability and reliability was one of the upper most design criteria. No machine would be released that a major tear down was required to service the machine.

Such should be a criteria for automobiles also.

P E H

The mechanic told me both were filthy, and considering they haven't been replaced since I bought it several years back, I had no inclination to doubt him.. And given that I didn't know WTF was wrong he could have done what dishonest or incompetent mechanics have done to folks I know, which is to go on a wild and expensive goose safari.. I really should take a picture of his yard, he's got MB, BMW, Porsche, even a Ferrari and a Lancia.. He's building a ponton Benz cabriolet from the primer'd body shell up..

I had this done at a dealership, and according to them they didn't have to remove the engine completely, just lift it enough to leave room for the pan to be removed. It's definitely more involved than any other car I've seen (VW, Chevy), and way beyond what I would try to attempt.

To be fair, though, I did end up getting a new suspension as well, I thought it was _supposed_ to ride low and I wasn't getting any sort of pogoing or bottoming-out in regular driving, but having it as low as it was may have contributed to the oil pan damage along with whatever random junk on the NJ Turnpike could have hit it.

Mat,

If the filters were so filthy, U might be concerned about fungus in the fuel system. It might be time for a Biobor treatment.

U might check the flow thru the fuel strainer in the fuel tank. Fungus will plug the strainer and the flow will diminish.

P E H

The W124 FSM talks about raising the engine slightly once it is unbolted from the mounts and that will give enough room for the pan to clear the frame crossmember.

__________________
Doug

1987 300TD x 3
2005 E320CDI

Riethoven,

The car I have to replace the oil pan is a '87 126. Any information replacing the oil pan on that model.

I don't always believe the FSM. The FSM for a '64 190D I had said engine had to be removed to R&R the oil pan. Actually the oil pan could removed with out too much trouble by loosenng the engine mounts, jacking up the engine and turning the engine so the crankshaft rod journals missed the end of the pan as it was moved to the rear. Heck, I even R&R the crankshaft without removing the engine. If I remember right, I put blocks of wood between the engine mounts and the frame to keep the engine lifted after I removed the jack from under the oil pan.

So I hope I do not have to remove the 603 engine, just loosen it and jack it up like I did the 190D.

P E H