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Discussion Starter #1
It was 8 degrees in Indianapolis this morning, but it has been getting progressively colder up 'til today. We have an attached garage so it is warmer inside where we keep our 1985 300D, but I'm curious. How would you describe a "normal" cold start procedure?

Here is what I've been doing...

Turn the key until the glow light goes off on dash, wait several more seconds

Repeat the above procedure two more times

Turn the ignition key and crank away until it "catches"

I'm concerned about the cranking away part. It sometimes takes 20 - 30 seconds for the engine to finally start and I'm afraid of burning out my starter (and stressing the battery). I replaced all our glow plugs last winter so there's no problem there. So is what I'm doing considered "normal"?

By the way, our car currently has a vacuum leak somewhere so that the engine runs on when the key is turned off. I don't know if this would be detrimental in any way for a cold start though (?).
 

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It was 8 degrees in Indianapolis this morning, but it has been getting progressively colder up 'til today. We have an attached garage so it is warmer inside where we keep our 1985 300D, but I'm curious. How would you describe a "normal" cold start procedure?

Here is what I've been doing...

Turn the key until the glow light goes off on dash, wait several more seconds

Repeat the above procedure two more times

Turn the ignition key and crank away until it "catches"

I'm concerned about the cranking away part. It sometimes takes 20 - 30 seconds for the engine to finally start and I'm afraid of burning out my starter (and stressing the battery). I replaced all our glow plugs last winter so there's no problem there. So is what I'm doing considered "normal"?

By the way, our car currently has a vacuum leak somewhere so that the engine runs on when the key is turned off. I don't know if this would be detrimental in any way for a cold start though (?).
A normal start would be:

1. Insert key into ignition
2. Pre-Glow until light turns off
3. Start engine cranking (1-3 seconds until fire)

This is how my 1985 300D starts up in single digit weather. 20-30 seconds of cranking is very bad and I suggest you find out what the problem is. Get some WD-40 and give it a quick squirt to help the engine start up. DO NOT USE STARTING FLUID!!!!

How positive are you sure that your glow plugs are working? Have you tested them with a voltmeter? How's the strip fuse in the relay box?
Mercedes Diesel Glow Plug Repair

Next thing to check on are the adjustments on the valves. When was your last valve adjustment done? Tight valves will make an engine very difficult to start.
Mercedes Diesel Valve Adjustment Procedure

In the winter I switch to Rotella 5w-40. A lighter weight oil helps a lot in cold weather because the engine isn't trying to pull a thick liquid throw a very cold engine. What type of oil are you using?

Finally, if your timing chain is crazy out of spec that will also cause issues starting.

Edit: A vacuum leak will not cause hard starts, but it will give you oddities with your climate control system. Most likely the leak is caused somewhere in the central locking system. Isolate the locking system and work backwards using the charts that are on this site. I'm posting on my blackberry, but do a search for "w123 interlock diagram".

Edit 2: If your compression is low this will also give you issues starting. Has this car been run on WVO?

And finally what is the year, model, and mileage of said vehicle? :)
 

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Discussion Starter #3
Great input. Thanks.

Our car seemed to start a lot like yours after we had some service done to it exactly a year ago, including the installation of new glow plus and a starter. The garage installed Bosch glow plugs. I doubt those would go bad in a year (?) so maybe there is something else at work as you suggest?

I have Kendall 15W-40 oil in the car. Our last valve adjustment was June of 2009 and we've put over 30,000 miles on it since then so I know it's due again. The garage (independent M-B specialty house) said a new timing chain would be a good preventative maintenance idea next time we adjust the valves, but that's even more $.

I've been out of work for 6 months with no income and am not a particularly effective DIYer (especially after reading about needing custom bent wrenches, cranking the engine over by different means, etc).

Our car (1985 300D) has 166K miles on it.
 

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1967 300
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Hmm, a valve adjustment should be done once a year. It's pretty easy to do and making the bent wrenches is pretty easy with a breaker bar and some propane.

I just did mine and 3 of them were out of spec.

However, theyre probably tight but they are probably not preventiting starting. I went 55,000 and 11 years without an adjustment and the car had issues starting at 8-10* F.

Check the condition of your glow plugs and battery. How does the starter sound? Is it fast, slow?

As with the motor oil, switch it to a lighter oil when you get the chance.

My first valve adjustment took me a day, but the second time around it was 45 minutes. I use the power steering pump pully to turn the engine. I'm too cheap to buy a 27mm socket for the lower crankshaft pully.

Oh yeah i'm a near broke college student. I do my DIY out of desperation. :p
 

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1982 300D Turbo, 126xxx miles
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x2 on the frequency of valve adjustments. I recently had the issues the OP was describing; I had to crank and crank just to start my car in 40 degree weather, so I knew that something had to be done. I recently adjusted my valves, and every one of them was tight, which leaves me to believe it hadn't been done in a very long time. It took me roughly a day to get it done, but I'm sure it will be a lot quicker the 2nd time around. I actually used the crankshaft bolt to turn the engine as described by the FSM, since I've heard on this board that using the power steering pulley will cause problems in the long run.

The results were like night and day; the engine fired up on the very first try, and I only glowed for as long as the dash light was on.
 

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1983 240D 3.0T
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I'm have the same problem. I've been having trouble starting below freezing. I've been glowing three full cycles (turn the key and way until you hear the faint click of the relay going off) and have had to crank for several seconds, I never crank for more than 10 seconds. Check your GPs again, although mine tested fine for resistance. I was told to check my IP timing.
 

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99 SLK230 Kompressor, 5 Speed Manual
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At that temperature there are a couple of things in play:

Your pin type glow plugs will have to be in top notch condition and the glow plug relay operating properly. In the eighties and early nineties they were as cheap as spark plugs, so when they got the least bit hard to start, I just slammed in a new set. Now that they are $7 a piece or more, it might be worth removing and examining them. It is possible for them to pass a resistance test and still be less than optimum condition.

Often you can remove one that passes the resistance test but you will find a hole burned in it.

The second issue at that temp is that diesel fuel gels at about 8 degrees F. In Texas we only have one grade of diesel. In your climate, you may have the other grade which prevents this, but I just want to make sure you are aware of this fact.

Hope this helps.
 

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30,000 miles can be enough for the valves to be tight enough to prevent starting. If you're not sure about adjusting the valves, checking the valve clearance is an easy first step, you just need some feeler gauges for that (and you'll need to turn over the engine). If some of the valves are tight, you've found the culprit.
 

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"Normal" winters here are usually within 10 degrees of freezing, it might snow but rarely. When the area was covered with it in January, all I did was cycle the glow plugs on the '85 a few times before cranking it over. My '83's previous owner informed me he had to plug his car in during the same time, but in the seven years he owned the car he never adjusted the valves.

I highly recommend using an anti-gel additive during the winter months if you live in an area that get's below freezing.
 

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More on fuel type: in some states they have #2 and #1 (more expensive) diesel fuel. For those cold temps you'll want #1, or 50/50. That's what they had in NE/IA/MO, etc. Here in GA they don't show a #, but it's probably a blend of the two. But below 10F, the car won't (or hardly won't) start with only #2. My point is, if you have the choice and you're putting in #2 to save $$, you'll have a tough time starting in the teen's and below.

Glow plugs: will glow longer than the indicator, as JEBalles was referring to. For at least '84 and newer, they reach their max temp quickly (2 sec's summer, 4-6 sec's winter), and the light goes out, but they continue to glow for, I forget - 10+ sec's total, definitely more than twice as long as the light is on - then you should hear the relay click off. The only time I've had a problem is last year the car had sat outside all day in the church parking lot after jumping on the vanpool van in the morning, started out at 15F and it never got above 35F. At end-of-day, it wouldn't start - I had a bad glow plug. In that same weather, after sitting out all day, with the new glow plug, it started right after the light went out. Then 2 more quit in the next two weeks. They lasted 25 years. But you could have one go bad after 1 year - sometimes things just go bad.

Block heater: do you not have one? This is a simple heater coil loop, like you see in the bottom of a simple coffee maker. It plugs in the right side of the engine block, and the cord goes along the side of the radiator behind the grill. I always use mine overnight if it gets below 40F. Except in the parking lot.

Valves: the reason tight is not good, is they tend to be open just a little longer than normal, meaning less compression, less starting ability. I personally haven't had a correlation experience between tight valves and poor starting in the winter.
 

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2013 MINI Copper S Clubman, '84 300CD-weekend car
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Try a couple of complete glow plug cycles. Around 30 seconds each, you'll hear the click.

See pic.

A 50-50% diesel and kerosene are also mentioned.
 

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Glow plug Relay.

I agree with the original response. Are you sure your glow plugs are working? I had this problem the first winter I bought the car. Second winter it wouldnt even turn over, 15-20 sec plugged in. I replaced the glow plug relay and haven't had a problem in 4 years, even replaced the plugs. I am going to in the next couple weeks tho after 4 years! As well as oil change and fuel filters. On the July/Dec. routine. Hope that helps.
 

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On the subject, slightly, of the block heater...is there any easy way to verify that the factory one is installed if you don't have a cord dangling out?

I know it's roughly mid-block between the starter and turbo on a 300D but, short of pulling either of those, I've never been able to put eyes on it while working on the vehicle.
 

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One more question, once started, say you stop at the grocery, run in and grab something, the whole thing takes 15 minutes, you have come in a vehicle that is up to temp, you shut it off, do your business, come back, do you go through this procedure on a warm motor? or just crank to start?

Mine by the way is a 300TD, and 82 year.
 

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If the engine is warm, you can start without pre-glowing, it all depends on the temperature of the engine. Engine temperature after 15 minutes depends on the ambient temperature, so in very cold climates such as Alaska or Siberia you leave your car running, in slightly less severe conditions you might need to wait for the pre-glow light goes out and in mild climates you can start right away.

The glow relay also has a temperature sensor, so when the temperature is high enough, the glow time is reduced.

If your car is in good condition, there should be no problem with starting.
 

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Thanks, my location though is North Carolina, and while there are 20's days, those are typically not days I would drive except for extreme necessity, so my question was more aimed at temperate days that involve typical 50's through summer weather.
 

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I didn't see anyone mention this, but I find that in Michigan, when I have to do a cold start (no block heater) when I leave work, it helps to press the pedal down about halfway while cranking.

(obviously, dont push it down so far that the engine over-revs before it has oil pressure)
 

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For such a mild climate, it is usually a key-only start. For cold days (below 30F) it sometimes is necessary to press the accelerator pedal a bit during or just after starting the engine. The turbodiesels with pencil glow plugs are usually good starters.
 

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20 degrees this morning, not even a full glow plug cycle, the SD started right up, no pedal. At work, no block heater either.
 

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I have fresh glow plugs in my '84 300TD, not even 1k miles on them. I haven't done a valve adjustment on the car yet. I fired it up on Sunday Morning (8 degrees + wind chill, probably -10, coldest day this year I think) - It hasn't run since christmas eve. I turned the key, waited for the light to go out, and it cranked for ONE second and started up.

I would put $ on one of your glowplugs being bad. Block heater will work, but it's obnoxious to have to always plug it in. I actually took my first 300 (coupe) off the road thinking it was dying... After not running for 6 months I turned the key in the summer and that one fired right up too...

Glow plugs make a HUGE deal, even one of them dead can make one of these cars start very hard. I've been through 3 winters now driving these old merc diesels daily, glow plugs are life!

Dave
 
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