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Old 01-07-2004, 12:29 AM
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Cold Starting????

I have a 79 300d mercedes and live in oklahoma where sometimes the weather is real cold during the winter. Well my battery is fine and everything, I'll even let the glow plug run 3 times before trying to crank it, then I turn the key and it is cranking and everything even with smoke coming out, but the damn thing won't actually start when it's cold outside. What can I do to make it start w/out getting a jump everytime b/c at school it has to stay outside. I need to know, thanks!

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Old 01-07-2004, 02:03 AM
Emu Rancher
Join Date: Mar 2002
Location: Washington, DC
Posts: 664
Try squirting some WD-40 into the intake that should help you get it going. If your battery and GPs are good i would check the starter.
W126 1983 300SD 286,000 miles and ticking
Baby blue exterior Grey MB tex
Recent work:
Replaced air cleaner mounting brackets and heat shields
Replaced alternator, fan and power steering belts
Replaced positive battery terminal
Replaced negative battery terminal and cord
New Duralast Battery

My car needs work.
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Old 01-07-2004, 02:30 AM
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How would it be the starter if it starts fine in warmer weather? I don't understand.
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Old 01-07-2004, 03:10 AM
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First off. Starting fluids like ether, WD-40, etc. are NOT for normal use. If you do use some DISCONNECT THE GLOW PLUGS FIRST! You don't want to blow up a precombustion chamber !

As for the starter. A weak starter may be enough power in warmer weather but in cold weather it might not have enough power to crank fast enough.

Don't forget, the glow plugs stay on 45 seconds AFTER he light goes out. Let them go for about 20-30 secomds before you start. If the school will let you go out to your car between classes or lunch, go start it and run at 800-900rpm for a few minutes. In an extreme times, get a remote starter. With this you can sart it from class or set it up to auto start every 4 hours. Most have a glowplug delay feature for diesels.

BTW, what city in OK do you live in?
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Old 01-07-2004, 08:26 AM
Join Date: Jul 2001
Location: Old Lyme, Connecticut
Posts: 3,596

This subject has just been addressed in some other threads in pretty good detail. If you try a search on cold starting you should find a lot of information.

The issue is that in cold weather the block is a very large heat sink, and if the engine spins too slowly the heat of compression, which the engine relies on to heat the air in the combustion chamber to a temperature sufficient to ignite the fuel, is absorbed by the block as quickly as it is generated. Also, all the normal compression leaks have more time to leak the pressure being generated by the piston motion away.

There are many things that cause the starter to lose its ability to spin the engine over fast enough. The age and use history of the motor in the starter is one, as lots of long cranking episodes will get the starter very hot. Its rating is based on running for a few seconds at a time, with substantial rest periods between starting attempts which keeps the motor windings cool. Lots of repeat, back to back starting cycles will drive the winding temperatures up above their design limits, which will degrade the insulation system and lead to degraded performance.

Another reason a starter will not provide the torque needed to spin the engine fast enough is a poor charging system and/or battery. As will a heavier weight oil since the starter motor is also providing the torque needed to make the oil pump work. The added drag of a more viscous fluid will increase the load on the starter motor.

So, if you have no problems starting in warmer conditions, you probably do not have any serious internal to the engine problems. But, do a search and look at all the possibilities. Good luck, Jim
1986 Euro 190E 2.3-16 (291,000 miles),
1998 E300D TurboDiesel, 231,000 miles -purchased with 45,000,
1988 300E 5-speed 252,000 miles,
1983 240D 4-speed, purchased w/136,000, now with 222,000 miles.
2009 ML320CDI Bluetec, 89,000 miles

1971 220D (250,000 miles plus, sold to father-in-law),
1975 240D (245,000 miles - died of body rot),
1991 350SD (176,560 miles, weakest Benz I have owned),
1999 C230 Sport (45,400 miles),
1982 240D (321,000 miles, put to sleep)
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Old 01-07-2004, 09:07 AM
Registered User
Join Date: Apr 2002
Location: Tulsa, Oklahoma
Posts: 103

I live in Owasso, Ok and boy has it been cold. The other morning it was 8 degrees. I recently changed my car over to synthetic oil and it has made a big change in the car's ability to start on a cold morning. She started up on the first glow, sure did puff a lot of smoke, but she started. I always leave the interior light on so I can watch it brighten as the glow plugs trip off. They are actually on longer than the little light on the dash says.

If you haven't had the valves adjusted in a while, you might try that. I did and it seemed to really help. I don't have a block heater, but I'm going to get one. I'm just afraid my neighbors ( I live in an apartment)might trip over the cord and sue me.

1982 300D
352,000 miles
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Old 01-07-2004, 09:31 AM
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Join Date: May 2002
Location: Central Oregon
Posts: 1,004
One other item.

If the timing hasn't been set in a long time I would also check it.
The timing can dramatically affect the starting characteristics of a car.
'99 S420 - Mommies
'72 280SE 4.5 - looking to breathe life into it
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'85 300SD Silver - Sold
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Old 01-07-2004, 02:29 PM
Posts: n/a
Thanks guys, well right now I have Castrol 20-50 I believe, something like that. And for the city in Oklahoma, I live in Oklahoma City and Norman, Go sooners.

Also I had another little question, what's the best way to get the door molding back on? It just popped off a couple months ago and not sure what the best way to make it stay back on would be. Thanks
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Old 01-07-2004, 06:18 PM
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Join Date: Jan 2003
Location: Reno/Sparks, NV
Posts: 3,063
Originally posted by Ohtooman
I always leave the interior light on so I can watch it brighten as the glow plugs trip off. They are actually on longer than the little light on the dash says.
Unless it's very noisy around you you can just listen for a click. When you hear it that's when the glow plugs stop heating.
2004 VW Jetta TDI (manual)

Past MB's: '96 E300D, '83 240D, '82 300D, '87 300D, '87 420SEL
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Old 01-07-2004, 09:52 PM
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well what I usually do is turn the glow lights on 3 times in arow before trying to start it, so do u suggest just waiting one time until the dome light brightens or what? Or do what I've been doing 3 times but also wait til the dome brightens before doing another turn on of the glow light?
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Old 01-08-2004, 12:57 AM
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Join Date: Nov 2000
Location: Vernon, CT
Posts: 1,848
20W-50 is way too thick for winter temps, especially the ones you are seeing. Look at your owner's manual it will list the appropriate weight oil for different temps. The most common diesel grade/weight is 15W-40. The owner's manual for my '83 300TD says 15W-40 is only good down to 23 F. So try using 10W-30 or a synthetic oil.
1999 MB SL500 (110,000 mi)
2004 Volvo V70 2.5T (220,000 mi)
2014 Tesla Model S 85 (136,000 mi)
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Old 01-08-2004, 08:34 AM
Registered User
Join Date: Oct 2001
Posts: 283
check your starter

You need a starter that can spin the engine nicely, not just spin it. I replaced mine a month or so ago, when I couldn't start it with weather in the twenties and had to get jumped a couple times. I formerly had to block heat my car in any weather below freezing.

This morning the weather hit 12, and I glowed it about 30 seconds and it caught and ran smoothly. No block heater.

Do everything else first: valve adjustment, glow plugs, filters--diesels need clean air and clean fuel to start well.

Test your battery under load, and if you aren't sure how old your battery is replace it. Some say that batteries that test okay, if older than five years, should be replaced.

I run synthetic as well, 0-40 in the winter, 15-50 in the summer.
1985 300TD 4-speed 212K
1992 400E 343K
2001 E320 72K
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Old 01-08-2004, 10:38 AM
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Yes, turn on the key and wait about 30 seconds then start. The glowplugs continue heating for about 40 seconds after the light has gone out.

Change your oil and use a 15W-40 API CI-4 rated oil. This grade of oil is acceptable for our Oklahoma climate. I don't believe your oil is diesel rated and the 20W-50 is too heavy for Oklahoma's coldest nights.

Check the water level in your battery, then give it a overnight charge. If you don't have a battery charger take it for a long drive on the highway.

Do you have any idea how your compression is?

When was the last valve adjustment?
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Old 01-08-2004, 04:18 PM
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Yeah I'm waiting for the next oil change to come up, it's real soon then gonna put in 10w-40 castrol, is this good enough?

I dunno about valve adjustments or compression lol

what do u do to get it to start when it's like in the teens or below? I usually let the glow light run 3 times in a row before starting.

At least I got some new shoes for the car now and no more slid'n around in the benz.
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Old 01-08-2004, 05:09 PM
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Originally posted by GANIMAL
Yeah I'm waiting for the next oil change to come up, it's real soon then gonna put in 10w-40 castrol, is this good enough?

what do u do to get it to start when it's like in the teens or below? I usually let the glow light run 3 times in a row before starting.
Change the oil now. The thick oil is making the engine more difficult to start. Make sure that the oil is rated for diesel engines. The first letter of the SAE rating will be C (for compression ignition) instead of S (for spark ignition).

Run the glow plugs once for 30 - 40 seconds, or until you hear the relay click off.

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