Hello, I am new to this forum and I wanted to ask around for some advice on my 1984 Mercedes 300d. I have this fairly weird problem that I was wondering if anybody knew how to fix. So there are times where my diesel will not crank, and I know for a fact that it is not the NSS. What made the car suddenly start is if i pull one of the power windows down and up and suddenly when I turn the key the car starts. I'm completely out of ideas on this one. The starter motor doesn't make any weird noises when it starts and the car itself starts almost instantly when i turn the key (when it works). I also want to know if anybody knows where I can get my fuel injectors tested. I have a rough idle, and I'm fairly certain that its one of the fuel injectors because it doesn't smooth out when the car heats up which means that the glow plugs are most likely ok.

Guessing w/out diagnostics a bad starter that coincidentally worked after the window up/down or a bad ignition switch. Temporarily install a test light to the starter and see if there is power when it won't crank.

For injectors our forum member greazzer is the expert, contact him.

Good luck!!!

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"Rudeness is a weak man's imitation of strength" - Eric Hoffer

Regarding your not cranking issue, I would pull the battery connectors and scrape them off with a wire brush and put some grease on them. I would also locate your grounds and clean them off as well. I think that should take care of that issue.

Dkr.

Questions are useless unless you mention where you are .

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-Nate
1982 240D 408,XXX miles
Ignorance is the mother of suspicion and fear is the father

I did then what I knew how to do ~ now that I know better I do better

Hi all, thank you for the replies.

First and foremost, I apologize for not providing my location. I live about 30 miles north of Los Angles, California, so there is little to no rust. The underneath of the car looks great.

I managed to get it to start consistently with the tips mentioned. Before I began my work (the fix of the starting issues i mentioned) a new problem arose. None of the interior buttons work anymore. All window switches, power sun roof, blinkers. The car still starts however. I checked all of the fuses and they are all good. I even swapped a few of them that looked corroded for good measure. I also tested the connections with the test light that I obtained. I have looked pretty much everywhere and I cant seem to find an answer, I hope to find one here.

edit*
Some switches do still work. I will list them here because they may help pin point the problem: right mirror joystick, stereo volume wheel, headlight switch, ignition, the interior lights still turn on(these are not switches but they work still), switch lights. And of course the stereo still works.

Thank you all so much.

Are your blinkers still signaling outside the car/ can you hear your relay responding when you hit the stalk? (I.e. no display at the cluster but still functional?)

In the meantime I’d say it’s time to pull out the multimeter, pick a switch and chase it until you find your break. Knowing the point of failure will give a lot more context for how to move forward.

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1985 300D Surfblau "Blueberry" 250K R.I.P
1984 300CD Manila Beige "The Banana" 238K R.I.P
1984 300TD Cypress Green "Olive" 390K (M.I.A.)
1982 300D Orient Red "Steak" 195K
1985 Euro 300TD Lapis Blue “Pancake” 200k KM
1982 300D Light Ivory “Butter” 183k
1984 300TD Black “Pepper” 55k

Hi thank you for the reply,
The blinker doesn't work in general. The headlights and tail lights still work however. The dash lights do come on as well. Also everything did work before today, and I do not think that all the switches could of possibly all broke at the same time.

One of the reasons for a rough idle can be the valve needed adjusting. Past owners who can't adjust the valves themselves usually won't pay a Mechanic to adjust them.

See the attached thumbnail.
For the Starter on the Fender Well in front of the Batter is a wire Terminal/Junction (it may still have the plastic cover on it). The 2 wires to the rear go to the positive terminal of the Batter and the front goes down to the Starter Solenoid and the Glow Plug relay.
You can use a jumper wire or attach a remote Starter and the Starter is supposed to crank the engine when it is jumped there.

If that does not work all of the time take a length of 2x4 and stick it down back where the Auto Trans Dipstick is on top of the starter and give the wood a few raps with the Starter. If that restores the starter to working then you have an issue within the Starter.

Not related to your specific issue but when I removed my Ignition Switch (found at the bottom of the Steering Colum Lock) I found that one side of the contacts was gone although it was still making contact with the base metal and working.

I also had the innards of the Steering Colum Lock causing a no stat intermittently but it failed completely after the innards broke.

In short look up stuff in the repair links and come up with a logical method of troubleshooting. Unfortunately there is not just one reason for the intermittent cranking issue.

As mentioned it would be a good starting point to see if when you turn the key to crank you are getting voltage to the Starter solenoid.

Repair Links
Fast navigation http://www.peachparts.com/shopforum/diy-links-parts-category/146034-fast-navigation-do-yourself-links.html

What I had to do to get rid of the my when Engine hot vibration/shaking:

Raise the Idle speed within the normal range (this helped some; it was around 700rpm). I raised it to about 750 rpms.

I bought a new Rack Damper Bolt but it did not help much. I have a turbocharged 300D Tubo and it has a Rack Damper Bolt.

Rebuilt my Injectors with new Nozzles (This took away most of the shaking)

Doing a Valve Adjustment (took away some more shaking). If you can adjust the Valves yourself do that first except for the new Valve Cover gasket is free.

Changed Motor and Transmission mounts (took away some more vibration)

Found that I had a small air leak that showed up when the Engine was hot due to hard fuel inlet lines that did not seal even with the clamps tight.

Finally was able to use the Rack Damper Bolt to tune out a little more shake. (that bolt was made to reduce the shake on a new engine; not to compensate for a bunch of worn and out of spec parts.

Attached Thumbnails

 

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84 300D, 82 Volvo 244Gl Diesel

Be patient the learning curve to gain information on these Cars can be really steep if you rush into it.

There is an adjusting screw that has a couple of names; Governor Idle Pin and Rack Dampening Screw are 2 of the common ones. It is there to remove some idle shaking.

The old ones tend to have weak springs and worn ends but it is not always the answer.

That being said to adjust the one you have back it out and as you do that the Engine will normally start shaking more at hot idle.
You adjust you idle speed not with the Rack Damper/Governor Idle Pin but with the Idle Adjustment Screw (in the repair links, and the idle speed is on one of the emission stickers along with the valve clearances and timing info).
Your model should have a tachometer. Once your idle speed is adjusted slowly screw in the Rack Damper/Governor Idle Pin with the goal of removing as much shakng as possible with effecting the idle speed. You idle speed is not supposed to be adjusted with the Rack Damper/Governor Idle Pin.

Not a very good pic but the arrow points to the Rack Damper/Governor Idle Pin on the back of the Fuel Injection Pump Governor Housing.

Attached Thumbnails

 

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84 300D, 82 Volvo 244Gl Diesel

Hi all,
I've already sorted out the rough idle with a diesel purge yesterday. Those injectors were a little clogged up i assume. The vibrations have come to a minimal.

My main issues now reside with the electronics. All of the interior buttons and switches have stopped working. The horn, headlights, roof lights and brake lights however, still work( probably because they are connected differently). Is there a central relay or fuse or something(im not familiar with electronic terms), that can stop all switches and buttons from working simultaneously? The dash lights also do come on when I initially put the key in, but when I start the car the battery indicator stays on. This could be an alternator problem(i think atleast). To further add details, the radio still works, the interior button lights work, the central locking system works, and the power steering still works. Every other button in the interior just does nothing.

The car cranks more consistently when its not blazing hot outside. I still have to do the test light thing when the car doesn't want to start. Currently it has not wanted to not crank. It used to be a very common problem but for some reason it doesn't want to show itself now.

In terms of valve adjustment, I completed one last winter. The car runs like a dream when it wants to actually crank. The previous owners luckily were informed enough to do regular valve adjustments, oil changes, etc. The car is able to power up hills and accelerate while doing so with ease. The highway near me, while heading north is a very long up hill drive, and the car was cruising wonderfully at 75 - 80 mph(tho it was quite loud since there are only 4 gears).

I thank you all for your kind considerations and help.

You need to test in the proper order .

#1 : the battery charge at rest, it must have at least 12 VDC in the morning before you start it .

#2 : check the charge voltage with the engkne running and nothing on .

Again, as soon as the engine goes above idle you must exceed 12.7 volts .

Yes, there are power relays but, until you discern the battery is holding it's charge and the alternator is putting out, you're wasting time to do anything else .

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-Nate
1982 240D 408,XXX miles
Ignorance is the mother of suspicion and fear is the father

I did then what I knew how to do ~ now that I know better I do better

I hope you didn't re attach the battery cable when the car was running....

An analog meter works better in older vehicle testing because multimeters often give false good readings .

Very often the alternator brushes are worn out and the rest is fine, it's a simple thing to replaced then on the car .

Just be certain to only buy BOSCH branded regulator/brush assemblies ! .

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-Nate
1982 240D 408,XXX miles
Ignorance is the mother of suspicion and fear is the father

I did then what I knew how to do ~ now that I know better I do better

Hi all,
Thank you for the previous help, here is an update.

No I did not reconnect the battery when it was running.

So it seems that the alternator was on its last leg when i last used the car because electronics didn't work when the battery was disconnected. I obtained the multi meter and put it to test and further confirmed that the alternator is in fact not putting out voltage. I suspect that it could be the voltage regulator that is faulty, because in my research the alternator doesn't commonly fail especially at my mileage(163, 000 miles).

After using the multi meter, the battery measured 12.46 volts idle and slightly less when the car was on.

Regulators frequently fail and are an easy DIY. Don't even need to remove the alternator, just make sure it is fully seated before tightening.

Good luck!!!

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"Rudeness is a weak man's imitation of strength" - Eric Hoffer

Yes, that is only the battery voltage, no charging at all.

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84 300D, 82 Volvo 244Gl Diesel