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Discussion Starter #1
Hi All,

About 3 years ago, I began putting 20W-50 oil in my 1983 300D turbo. I switched to this thicker oil because I have a few leaks and figured it might slow them down a bit. I can't really tell if the leaks have slowed down, but I've been using this oil ever since. The last two winters, though, I've had trouble starting the car when it's cold. In fact, toward the end of last winter, I had to replace the starter and the battery, since the difficulty starting caused the battery to go bad (it was already pretty old, though). I figured the root problem was just the starter going bad after 300,000 miles of use. With the new starter, the starting difficulties went away. Now that this winter's here, though, I am having troubles starting again. I wouldn't think the new starter is bad already. Could it be that the 20W-50 oil is too thick, and that it has been the culprit all along? When I heat the motor for 20 minutes using the built-in electric heater, the motor starts just fine. I interpret this as primarily being due to the heat decreasing the viscosity of the motor oil; further evidence that the problem is the 20W-50. Any ideas?

The last two times when I have had problems starting it, the temperature was right around 32 F. This is the bottom range suggested in the MB manual for this temperature (see attached scan).

Thanks,
AEM
 

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I'd say 20w-50 is pretty thick for cold weather. When it gets particularly cold here (which isn't often) like down into the 20's and teen's my 240D will be a little slow to crank over first thing in the morning and I'm using 15W-40. Looking at that chart you'll notice that 15w-40 covers a fairly broad range of temperatures but you'll see that around 23°F it's at the lower limit of use. 20w-50 on the other hand has a low temperature limit of 32°F, which means that going any colder than that you'll be dealing with really thick oil. If you're in an area where it gets considerably cold and stays that way for the better part of the season you should change your oil with something thinner so that the engine can crank over easily. Once the warm weather returns change the oil back to the thick stuff to keep the pressure up.
 

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Discussion Starter #3 (Edited)
Thanks, Matt. I happen to also live in the Bay Area (Los Gatos). I just tried starting my car after letting it sit outside for the day without any running. It's only 44 F and it still won't turn over. Two days ago, after having it sit in the garage (where it's warmer) for 1.5 weeks without any running at all, it started without incident. I just don't get it. Anyone have any other ideas about what the problem could be?

The starter is less than a year old. The battery is less than a year old and is a nice Bosch battery that's appropriate for the car. I believe the starter and battery connections are solid. The glow plug light on the dash lights up like normal (I was told that if two or more glow plugs are out, it will not light). I used a multimeter to test the relay switch going to the glow plugs (I believe that's what it's called), and all the glow plugs/connections appear to give appropriate resistance. In January, I also replaced the two shifter bushings on the shifter rod because there was toggle in my shifter and it wasn't coming out of park easily. I have read that shifter bushings under the console can also cause difficulty starting. But would this be dependent on the weather, like in my situation? I have also tried starting my car in both park and neutral, with the same discouraging results, suggesting to me that the neutral safety switch is not the problem.

I just replaced one of the rear axles, and to now have this problem is just killing me! :confused:

AEM
 

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It's good to see more Bay Area folks joining here lately. Welcome.

When's the last time the valves got adjusted? How's the compression?

Let's also clarify, by not turning over are you saying it's not firing or is the starter not even engaging? Those are two entirely different issues. The latter is a common one when dealing with rebuilt or refurbished starters on these cars. For whatever reason some are just dead on arrival. In a lot of cases it's a bad solenoid and not the actual starter motor itself.

Now, what I suspect is going on based on the fact that your car has a tough time in colder temps yet it does ok if it's been in the garage, is that there could be a compression issue, but just to be sure it'll help to rule out fuel and air delivery problems first. Start with fresh clean filters and no ways for air to get into the IP. Next is to adjust the valves which should be done every 10-12k miles with the engine cold. Next is glow plugs which can be tricky since the resistance value doesn't always tell the full story. I had 2 on my 240D that checked out ok on the meter but when I pulled them out and tested them individually they took way too long to heat up. The pencil style plugs should only take a matter of seconds to fully light up. If all of that stuff checks out I'm thinking sticky piston rings.
 

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When its hot weather, they perform ok, even with old/small battery, bad compression, in need of valve adjustment, old glow plugs/relay, thick oil, old/clogged air/fuel filters and dirty injection.

When its hot, if all of the above was taking care of before the winter, they fire up beautifully, in most cases.

I fired up mine at 38F, it was a little rough at idle, but that is why they put that idle adjustment thingy at the left side of the steering wheel.

What kind of battery you have? I have an OEM from the dealer, its HUGE! I left the car with the lights on for 2 hrs today and started right away!

Oh, and I use 20w50 as well, and I add "stop smoke" which makes it thicker" :p
 

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Discussion Starter #6 (Edited)
When's the last time the valves got adjusted? How's the compression?

Let's also clarify, by not turning over are you saying it's not firing or is the starter not even engaging?

Start with fresh clean filters and no ways for air to get into the IP. Next is to adjust the valves which should be done every 10-12k miles with the engine cold. Next is glow plugs which can be tricky since the resistance value doesn't always tell the full story.
It's been a long time since I got the valves adjusted. I myself did it about 3 years ago. Actually, I followed a tutorial I found on this website; when I took off the valve cover and put the feeler blades in, the gap distances seemed to be just right; so, technically, I didn't really adjust the valves--they seemed good.

I am not sure about the compression. Is there a way homespun way I could test the compression, or would I have to take it to the shop?

As for what's actually going on, the starter is effectively engaging; it just isn't managing to get the motor to start, even though the motor is turning over and struggling to start.

For filters, I recently replaced: air filter and fuel filter (both external and in-tank). I also flushed the fuel line and it hasn't been all that long since I replaced the oil filter, either.

I replaced the glow plugs about 3 years ago. The dash glow plug light does take a little longer to turn off when it's cold out, for whatever that's worth.

One last symptom: Since about 1.5 years ago, the only way I can start the car and prevent it from dying within several minutes after start is by pumping the fuel pedal a few times followed by holding it down slightly as the engine warms up. If I don't pump the pedal before trying to start, the car won't start. If I don't hold the pedal down slightly for several minutes after starting, the engine will run real rough and shaky and will eventually putter out. Once the car is warmed up, and whenever starting throughout the rest of the day, none of this is generally necessary.
 

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When its hot weather, they perform ok, even with old/small battery, bad compression, in need of valve adjustment, old glow plugs/relay, thick oil, old/clogged air/fuel filters and dirty injection.

When its hot, if all of the above was taking care of before the winter, they fire up beautifully, in most cases.

I fired up mine at 38F, it was a little rough at idle, but that is why they put that idle adjustment thingy at the left side of the steering wheel.

What kind of battery you have? I have an OEM from the dealer, its HUGE! I left the car with the lights on for 2 hrs today and started right away!

Oh, and I use 20w50 as well, and I add "stop smoke" which makes it thicker" :p
Once I was working on my car and left the plug that goes into the back of the alternator unplugged and drove it around all day the next day starting it up multiple times too and didn't notice anything wrong until when I was driving home and the lights started going dim:rolleyes:
 

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You should change the oil filter every time you change the oil.
It's been too long for a valve adjustment. Do this first. If the valves clearance are all over the place then your compression will be miserable.
Second, Diesel purge in case your problem is spray pattern and injection.
Third, sometimes a piece of gunk is all it takes to clog the filters.
What about your tank screen?
 

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Discussion Starter #9 (Edited)
You should change the oil filter every time you change the oil.
It's been too long for a valve adjustment. Do this first. If the valves clearance are all over the place then your compression will be miserable.
Second, Diesel purge in case your problem is spray pattern and injection.
Third, sometimes a piece of gunk is all it takes to clog the filters.
What about your tank screen?
Okay; I will definitely check the valve clearance.

I will also pick up some diesel purge.

When you say the "tank screen," are you referring to the in-tank fuel filter? A few months ago, I removed the entire fuel tank and cleaned off the in-tank filter.

I think I'll start with the easiest move first and just replace the little external fuel filter again--I happen to have one handy, and the current one is a bit cloudy.

Oh yeah, the battery is a Bosch Premium Power (CCA @ 0 F: 850, CA @ 32 F: 1000, RC Mins @ 25A: 120). I just measured the resting voltage to be ~12.5 V.

Thanks
 

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Discussion Starter #10 (Edited)
So, I just replaced the inline fuel filter and tried to start the car at 55 F. No luck. After heating the block for ~20 min using the built-in electric heater, the car started without incident. After letting it sit for 20 minutes, it started just fine. After letting it sit about 45 minutes, again, it started fine.

The battery voltage reads:
Before starting = 12.5 V
During starting = sags to 10.5 V
While idling = reaches 13.8 V

So, it seems the battery is good.
 

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?

I use 20/50 Castrol in my 190D 2.0 ltr and have never had a problem with starting. When the temp lately went down to 28 degrees, it fired right up immediately. You must have a problem elsewhere.
Hemersam
 

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Discussion Starter #12
I use 20/50 Castrol in my 190D 2.0 ltr and have never had a problem with starting. When the temp lately went down to 28 degrees, it fired right up immediately. You must have a problem elsewhere.
Hemersam
Great. Thanks for the input. At this point, I guess it's just a matter of finding out what the source of the true problem is.
 

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What's the specification on the battery, is it the correct group/size?

What glow plugs do you have and how old are they?

Factors to consider when starting from cold:

1. Good compression (valves adjusted properly)
2. Good battery & starter (proper battery size, capacity and age)
3. Good glow plugs and relay (Bosch or Beru plugs, relay in good order, strip fuse intact)
4. Good filters and fuel (filters not clogged, fuel system primed, and fuel not gelled)
5. Good block or engine heater (as a supplement to the above)
 

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Discussion Starter #14 (Edited)
What's the specification on the battery, is it the correct group/size?

What glow plugs do you have and how old are they?

Factors to consider when starting from cold:

1. Good compression (valves adjusted properly)
2. Good battery & starter (proper battery size, capacity and age)
3. Good glow plugs and relay (Bosch or Beru plugs, relay in good order, strip fuse intact)
4. Good filters and fuel (filters not clogged, fuel system primed, and fuel not gelled)
5. Good block or engine heater (as a supplement to the above)
Thanks. Although I don't remember all of the specifics of the battery, I am pretty confident that it is a correct fit for the car, as I did look into it thoroughly before purchase (here's what I know: Bosch Premium Power, CCA @ 0 F of 850, CA @ 32 F of 1000, and RC Mins @ 25 A of 120). The battery and starter were purchased and installed by me in January of this year and have not posed any other problems thusfar.

The glowplugs are Meyle, purchased through Performance Benz. All new ones were installed about 3 years ago. About 1 year ago, before putting in the new starter and battery, I used a multimeter to test the plugs and relay connections; everything tested just fine. I did not test each plug individually by removing it, however.

Around January, I replaced the in-tank, in-line, and main fuel filters, cleaned out the fuel tank, and cleared the fuel lines. I am sure the fuel isn't gelled or filled with algae, as I use an algacide and have never seen any signs of gelling in almost 30 years.

The one thing I haven't done in 3 years or so is adjust the valves. I plan to do that very soon. It's weird, though, because when I had this same problem last winter, it was replacing the starter that fixed everything (I only replaced the battery because the bad starter killed it). I'm starting to think that the starter wasn't the base of the problem, and that it was something else that killed that last starter, which, in turn, killed the last battery. I sure hope the same thing isn't happening all over again; but, it sure seems like it. When the car is pre-warmed, it runs just fine; although, when I turn it off it does seem to die a bit rough sometimes.
 

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I'm surprised Meyle glow plugs are available. If you read through the archives only Bosch or Beru are most recommended. Other plugs have bad reputation, including Autolite, Champion, and Monark.

My suggestion is have the valve adjustment done. Since you'll be in the general area, might as well pull and inspect the plugs individually. Get the proper reamer to remove the carbon inside the GP holes. Be ready to replace any plugs that you find to be bad.

We basically have the same car ('83 300D turbo), but I use 15W-40, the glow plugs have been replaced in 2005 with Bosch 80006 units, valve adjustment was done last year (not much driving for me) and battery is the proper MB unit. No problems starting in 45F temps.
 

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I'm surprised Meyle glow plugs are available. If you read through the archives only Bosch or Beru are most recommended. Other plugs have bad reputation, including Autolite, Champion, and Monark.

My suggestion is have the valve adjustment done. Since you'll be in the general area, might as well pull and inspect the plugs individually. Get the proper reamer to remove the carbon inside the GP holes. Be ready to replace any plugs that you find to be bad.

We basically have the same car ('83 300D turbo), but I use 15W-40, the glow plugs have been replaced in 2005 with Bosch 80006 units, valve adjustment was done last year (not much driving for me) and battery is the proper MB unit. No problems starting in 45F temps.
good advice. Pretty sure a plug or two is out on my wagon. Yet it still starts on colder mornings. Had valves adjusted last month...
 

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I'm surprised Meyle glow plugs are available. If you read through the archives only Bosch or Beru are most recommended. Other plugs have bad reputation, including Autolite, Champion, and Monark.

My suggestion is have the valve adjustment done. Since you'll be in the general area, might as well pull and inspect the plugs individually. Get the proper reamer to remove the carbon inside the GP holes. Be ready to replace any plugs that you find to be bad.

We basically have the same car ('83 300D turbo), but I use 15W-40, the glow plugs have been replaced in 2005 with Bosch 80006 units, valve adjustment was done last year (not much driving for me) and battery is the proper MB unit. No problems starting in 45F temps.
Lower quality Glow plugs can loose the tip in the cylinder and as their metal may be harder than specified, they could score the piston and then game over.... by the way: How is your oil consumption? do you burn a lot?

I bought this awesome reamer from MercedesSource, and worked perfectly... I ended up giving it to a friend that works in this cars.

Heavy Duty Carbon Reamer for Pencil Glow Plug Chambers | MercedesSource.com

This is how I did it, perfect timing to change your hand primer pump for a bosch if you haven't yet, and have a set of Bosch or Beru glow plugs handy just in case... if u dont use return it, but if you need it you have it:

12mm ratchet box wrench
17mm combo wrench
15mm combo wrench
8mm combo wrench
12mm nut
Screw driver
Bosh glow plugs
Reamer


1. I took all the vacuum stuff away so I could access the fuel pump hard lines.This included the MAIN vacuum HOSE to avoid braking those plastic "T" things.

2. I removed the "cigar" return fuel line.

3. I loosen the injection lines (17mm) at the injectors and then the ones on the pump.
Here is a trick, to release the ones in the pump, I had to use a 15mm to hold the delivery valves. I didn't realize this in the beginning and I was turning the whole thing including the fuel line which got twisted but came back to normal.
I used painters tape to cover the valves and injectors in order to avoid contamination.

4. Removed the small nuts holding the cables for the glow plugs, 8mm.

5. 12mm ratchet box to get the old glow plugs out. They wouldn't want to come out, carbon build up was trapping them. Took some effort.

6. Used the reamer and the lil brush, and it worked perfectly.

7. reinstall everything back, left the injector fuel line a little loose to torque the engine and get rid of the air. When I saw fuel coming out of them, I tighten them up.

8. diesel purge and new filters





:D
 

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Discussion Starter #18
Hi All,

Thank you everyone for all of your input. I adjusted the valves and have not had any difficulites starting my car for the last 3 days.

AEM
 

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Hi All,

Thank you everyone for all of your input. I adjusted the valves and have not had any difficulites starting my car for the last 3 days.

AEM
That's great news! I remember when I adjusted mine for the first time right after I got the car I couldn't believe how much difference it made. Starts smooth, runs smooth, idles better, and has better power. Now, granted my w123 is a 240 so it ain't got much to begin with but holy cow it felt like a brand new car again.
 

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Oil film strength and robustness have improved since the printing of that manual. While the low-temp characteristics still remain true, the higher-temp ones may not as much. I'd personally run a 5w-40 HDEO year round. In the bay area, its fairly mild, so you can consider running 15w-40 year round.

You want to be shoppng in the diesel oil section, not the API "S" oils, the add packs are substantially different. For a sooty diesel, the HDEO is the way to go.
 
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