82' 300D rookie
 

Hello all. I am new to merecedes and this forum. A couple of days ago I traded my volvo wagon for a 1982 Mercedes 300d. The body is in good shape and the motor seems to be sound but it has spent the better part of the past 4 years, parked. I will be going over the engine the next few weeks and tuning things up a bit.
As it is right now, it's slow to start and seems to idle pretty rough. When I give it more fuel, the rattle evens out a bit. It is slow on the take off and the pedal is hard to press, but once up to speed its fast. The shift into second is a little hard when gunning it ( will even squeak the tires ) and the front drivers side and rear passenger side windows do not roll down. Also, the car won't shut off when the ignition is off. I use the lever under the hood.
Could the hard shift, windows, and no shut off be from a vacuum leak in one location and does anybody know where to start looking? I am going to replace the filters, adjust the valves, tighten up the linkage, test the glow plugs and what ever else you all recommend. I pretty happy to have this car and will be converting it to wvo this coming spring.

I appreciate any help or suggestions you all may have and hope that some day I will be able to contribute to the forum as well.

Buy a mighty vac and find a schematic to the vacuum lines to start troubleshooting. Sounds like you got a vacuum issue.


Here is the manual you need, courtesy - Mercedes Benz.

look under w123

Thank you for the reply and advice. The link you attached does not work, do you know the address for the manual?

I hope you have new fuel filters. 4 yrs worth of gunk in the old ones is not a good thing.

Welcome to the forum !!

Hard shift is low vacuum. Simplest troubleshooting procedure is to unplug the door/trunk system under the hood, plug the place it was plugged into with a golf tee and see if the engine shuts off. That line exiting thru the firewall is yellow. If engine shuts off, leak is in that yellow door/trunk system. Then do the same thing with the green line--climate control system. If unplugging both of those systems don't solve the problem, the leak is under the hood.

Lubricate the accelerator linkage balls. Don't adjust it much. It's intended to have movement in the pedal before you get increased engine speed.

Could be a bad fuse on the windows or dirty switches.

Thank you. I unplugged the two yellow lines and covered the holes and it shut off. So now I need to find where all those lines go. Are there any diagrams around that show the door/trunk system? Do you guys recommend a certain manual and set of tools for this car? Right now I
have nothing as far as a manual goes. I have plenty of tools but none specific to the car. Thanks again. Also, where is the fuse box on this puppy? Thanks

Fuse box is under the hood on the left near the brake booster. Vacuum diagrams are on here. One way to test the door lock system is to hook it back up start the engine so you have good vacuum, get in the car and lock and unlock the driver's door. Observe the other doors to see if they lock or if there is hesitation. If there is, there's probably a leak in the vacuum pod on that door. Eventually you'll need a Mity Vac to test things. Those yellow lines run to the driver's door and then under the floor mats.

try again:

startekinfo

Go here and select Star Tekinfo

then

MB Workshop Resources

Then scroll down till you get to Model 123 Service Library and open it. Schematic should be in there somewhere.

There are a couple stickies for vacuum diagrams. I customized one for the coupe that'll be similar. Do an advanced search for the word "definitive" by yak.

Nice, Thank you.

The Vacuum leak issue can also be related to your no shut off issue.

Pull the Brown Tubing off of the Rear of your Fuel Injection Pump and check to see if there is Motor Oil in it. If so the Diaphragm of the Vacuum Shutoff is starting to go South.

Attach a separate Hose to it and while the Engine is running and either simply suck on it or use the Mighty Vac (hand held Vacuum Tester that you can pump) and see if the Engine will shut off. If it does not shut off you clearly need a new Vacuum Shutoff.

There is also another Vacuum Shutoff valve located on the Steering Colum Lock. You will see another mostly Brown Tubing (I do not remember which brown tubing has the stripe on it) going through the Fire Wall. It will be the one that connects to the other Vacuum Lines.

While the Windows not moving can also be an issue with the Switches (they can be taken apart and the Contact Points cleaned/scraped).
The Door Panel can be removed and you can connect the Window Motor drect to a Battery to see if it works.
Unlike your Starter Motor the Window Motors do not use a ground to the Chassis as part of the circuit.
Connecting the Window Motor Wires to a Batter and the Window will go one way. Swapping the position of the Wires will make it go another way.

Check your glow plugs, properly operating ones should provide easy starts, if you have even decent compression.

Thanks for the reply. When I disconnect the yellow line on the yellow splitter that goes through the firewall and plug it, the car shuts off. Would this rule out the Vacuum shutoff? I checked for oil in the brown line and did not see any. Could the windows also be related to the yellow line that has the leak? Thank you for your help.

Yep, I am going to replace the glow plugs. The battery needs to be replaced as well. I have to jump the car with my F350 diesel and it takes a long time for it to fire. Once the car is warmed up, it turns right over. The start may be on its way out as well. After cranking for a bit, it makes a funny noise while turning off ( at least I think its the starter making the noise ). Do you recommend a certain brand of glow plugs?

Windows are electric. Not connected to vacuum.

Thank you all for the replies. I really appreciate it. While I'm at it, I might as well ask you all what fluids you use. I am going to be giving the car an oil change, flushing the tranny, flushing the coolant, and the break lines. I have no manual ( will pick up a book asap ), but usually these forums have the best advice. Also, what glow plugs? And any other suggestions for a car that I have no history on and likely sat for most of the past 4 years. Should I add anything to the diesel tank? The filler cap was dang near rusted on. Fortunately, the rust was just in one little spot but I'm sure the fuel gathered a little water over the years. Thanks again.

Attachment 99457

Diagonal inop windows usually mean a fuse. Check one of the ones in the corners, they've got letters a-d, not numbers.

The alternative fuels forum has info for future plans. There are a few techniques for draining or flushing the tank. There's a fuel strainer that you may want to swap. Possibly consider new viton lines if you're going bio-D or WVO.

Clean and check fuses. Clean the crap out of the hinge drains. Check your front suspension and read up on the M-B spring compressor. Welcome to W123 ownership.

Thanks for the tips. As far as converting to wvo, I will be using a two tank system. I am not sure how to plumb it yet, but I did convert my 7.3 powerstroke 90,000 problem free miles ago. I used a kit for the conversion but have gained a fair amount of knowledge since then. I will be doing a DIY for the Benz. I am real happy to have this car and eager to learn more about it. Hoping to find a wagon someday.

W123 vacuum interlock diagram
 

Here is a post from a thread on the w123 vacuum Interlock diagram.

http://www.peachparts.com/shopforum/1247118-post5.html

Charlie

Thank you, that is very helpful. Is my car a w123?

It is.

Okay, thanks. I can't see how it would make a difference, but, I noticed in the diagram that the yellow splitter is on one of the outer branches of the 3 way part of the vacuum line, on my car it is on the center of the 3 way split. I'm sure it shouldn't matter but thought I should check.

Also, I am having difficulty find the fuse box. I found a box with a couple of relays but no fuses.

Hmm
 

Hmm, if you still haven't gotten it started, try a carbon reamer. You take out the glowplugs and ream the carbon out of the glowplug holes. Here is a site that you can buy the reamer from, and they tell you tons of info. Good Luck!!

https://**************.com/node/2842

Fuze box
 

The fuze box on my car, I think it would be in the same spot on yours, is next to the brake booster. Right under the hood, driver's side, little black cover with two long screw-type-things. If you need, I can take pictures of mine. Again, Good Luck!!

The only thing important is that line getting full vacuum. The two nipples on the main vac line may/should have different amounts of vacuum. ~22 and ~15 inHg. You want as much vac as available.

As far as fluids go, that's usually a can of worms, but I just switched to synthetic. Just be sure to use a diesel rated oil.
Otherwise, I use name brand stuff available at the local AutoZoo.

I've use Bosch glow plug. Stay away from Autolite!

There is the Factory Service Manual available sometimes online, but I bought mine from MB. They are more difficult to track down now, but should be around.

The fuel system will need attention. At worst a tank flush. As mentioned, there is a strainer in the bottom of the tank, it can be cleaned and reused. You'll go through a few filters at first too, both the clear inline one (primary) and the spin on one (secondary). On the banjo bot holding the spin on filter, there are two rubber "O" rings, replace 'em.

Replace the fuel cap. I use an oil cap I picked up from the junk yard. You can get new a gasket for it. Water, condensation, has spent some time in the tank, so at least a dewater treatment, then a fungicide is a good idea.

This antifreeze:
Valvoline.com > Products > Zerex > Antifreeze Zerex > Zerex G-05® Antifreeze / Coolant

DOT 3 or 4 for the brakes, do not use silicone based stuff, it doesn't mix well with what's in there now.

The fuse box has two large knurled knobs on it, it takes some time to get it back on, but clean the contacts and replace all fuses. It is on the fire wall, beside the brake booster. See pic.

Someone mentioned to use a reamer on the glow plug holes, see pic.

Thank you for the good information. It really helps a lot.

Yes!
 

Yes, somebody was able to get a picture! Sorry about that!! Good Luck and God Bless!

82 300d and 84 300d interchangeable?
 

I have an opportunity to pick up an 84 300d for real cheap. The body is a bit rough, but it has a lot of new parts. The parts would swap out with my 82 300d right?

Not all will but certainly most will.

So what else besides glow plugs would make the car really hard to start? Once its started it idles real low and rough. Once the car has been driven and warmed up it seems to start no problem after cycling the glow plugs, hard start if I don't cycle the gp's. Is there something else I should check out before changing the gp's. Thank you. It is also very slow acceleration until I going 20 or so.

Welcome! I'll probably get howled at for this, but it's something my wife noticed about the shifting on ours. If it starts getting low on oil, it shifts later. I thought she was goofy, but I have to admit she's right. Since mine has a few leaks and blowby issues, I do have to ad oil after long trips. And those glow plugs definitely need changed. Even if they test good, you can keep them for back ups, but just starting out, I'd change them all. Also, everybody has mentioned the vacuum issue, but if this has set for years, I would go through and not only check for cracks, but for then ends of vacuum hoses that can dry rot and not have a tight fit anymore. (Been there, done that). The two yellow lines are leading to doors, trunk and fuel door locks. I don't even use my trunk or fuel door locks. Might want to look at your engine\tranny mounts. That might have a little to do with your rattling\shaking issues. (Also the engine shocks). There are also small (cheap) bolts that hold the air filter housing on that can make lots of noise if loose or broken. Another thing to check for rattling are the exhaust hangars, which are basically rubber donuts (cheap and easy, also). If they're gone or dry rotted, get new ones. To make them easier to put on, put them in a pan of hot water for a few minutes. That will help there. Ok, then, good luck and expect to get answers and help like you wouldn't believe on this forum. It's been a real life saver for me! Good luck! Lee

Thanks for the advice.

There are several threads unique to hard starting with a lot of info. Since the car is new to you, get the basics done to establish some form of maintenance reference baseline. If you converted a powerstroke and drove it for 90k, you've probably got a fair amount of diesel knowledge already.

Verify all 5 GPs and the relay are working correctly is the basic start.
A strong battery and good connections to the starter to get good rotation and compression helps. If the battery is weak or you've got a drain (trunk or dome lights stuck on? something else?) then it may be harder to start after sitting.
A proper valve adjustment should be on you short list of near-term things to do.
An oil change with a quality oil in the proper weight.
How's the air filter?
Clean fuel and clean filters.

If it doesn't start on reasonable temp days with the basics done, then a compression test and a leakdown test may be in order to evaluate the condition of the engine.

Learning the MB language and the references for your car will help in searching and weighing the advice, you've got a W123 body style with a 617 motor (of some 617.xx variety, or OM617) and a tranny designation that escapes me for the moment.

Thanks again for all the help. I do have a bit of knowledge about diesels and am thrilled at how easy this Mercedes is to work on. I have a good understanding of this engine just by looking at it. The powerstroke is still a great truck and daily driver for me. I use it to haul boats and campers around the country. Its got 290,000+ miles and runs strong. I do most of the wrenching on it.

I have giving the w123 a oil change and replaced the fuel filters. I also plugged the vacuum line for the locks/trunk and no it shuts of shortly after I turn the key. I am going to check out the glow plugs and set the valves this weekend if I have time. I was reading somewhere on here about adjusting the Rack Dampener Bolt may help with hard starts and rough idle. I'm not sure how to adjust it but should be able to figure it out. Hopefully its just the glow plugs. I may try and clean the injectors this weekend as well, if I have time. Thanks again for all your help. Where should I start looking for the hard tranny shift. Its really not to bad, but I want to do a flush soon and would like to have it operating as it should.

Usually, hard shifts are due to too little vacuum.

So I plugged the car in last night because the temps have dropped. Its probably 15-20 degrees out. The car fired right up this morning :D. The idle was still rough but, I have to believe with a new set of gp's and a valve adjustment, this puppy will be good to go. Now to track down the vacuum tranny issue. Also, It has green coolant, do I need to change that right away or can it wait until spring? Also the instrument cluster lights don't work nor does the rpm gauge. I appreciate all the help.

So far so good.

Make sure the VCV is getting some vacuum.

Please put your car in your sig or avatar, I've forgotten!

Thanks. I added a Avatar and a signature. I will look up what the VCV is.

Good,
http://www.peachparts.com/shopforum/diesel-discussion/304667-alda-removal-2-large-nuts-300-sd-1981-a.html

See pic, the round white item on the right. It controls the amount of vacuum the transmission receives, there are many posts about it.

dash lights = rheostat (or try carefully rotating the odo reset to see if that'll clean it up). search and you'll find how-to's on rebuilding or jumpering.