Hi everyone hows it going? This is my first post in this forum and have joined due to a new addition. My brother bought an '85 300TD wagon in Tennessee and drove it all the way back to frigid central NY. In the colder weather the thing really has a hard time starting, it has taken us 10 minutes to start it in this colder weather and because of this we have not driven it much. I have a diesel VW Passat which starts right after the glow plug lights go out first time everytime. I tested the glow plugs and they lit up the tester light. Anyways I am just wondering if this is a common issue on these cars and what are my options to make this thing start easier or more reliably. I am trying to avoid a plug in block heater. On another forum I went on I think I heard of someone having a push button glow plug activator where you could hold it down as long as you needed. Is anyone familliar with this? Would my stock electrical system be able to handle this? Any other advice would be great! Thanks

There are a number of things you might do to improve cold starting. Adjust valves, new glow plugs, ream the glow plug holes, good battery, make sure starter is spinning engine fast enough. A lower radiator hose heater (1 1/2") is cheap, (Ebay $15--Zerostart) simple to install (half hour) and will reduce strain on your starter and battery in cold weather.
A compression check could tell you where you stand in optimizing cold starts.

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1977 300d 70k--sold 08
1985 300TD 185k+
1984 307d 126k--sold 8/03
1985 409d 65k--sold 06
1984 300SD 315k--daughter's car
1979 300SD 122k--sold 2/11
1999 Fuso FG Expedition Camper
1993 GMC Sierra 6.5 TD 4x4
1982 Bluebird Wanderlodge CAT 3208--Sold 2/13

Welcome and good luck with the new wagon.

I sometimes need to glow the plugs twice in very cold temps. You should do a valve adjustment and switch to a lighter weight or synthetic oil for winter. Cold, thick oil makes for tough starts due to low compression. Valve adjustments are vital to engine health, easy starts and less smoke. I would try these things prior to altering any stock systems.

Also, look in the owner's manual ... there's a cold weather start-up procedure that MB recommends. I believe it's 3 pushes on the pedal to the floor with a long glow and you should start right up.

PS: I posted this in the other forum you asked in. This forum is much more active and has more w123 members that can help.

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Chad
2006 Nissan Pathfinder LE
1998 Acura 3.0 CL
OBK#44
"Pleasure in the job puts perfection in the work." - Aristotle (384-322 B.C.)

SOLD
1985 300TD - Red Dragon
1986 300SDL - Coda
1991 - 300TE
1995 - E320
1985 300CD - Gladys

Welcome to the forum, Pedro. That's a great car you've got.

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" We have nothing to fear but the main stream media itself . . . ."- Adapted from Franklin D Roosevelt for the 21st century

OBK #55

1998 Lincoln Continental - Sold
Max 1984 300TD 285,000 miles - Sold
The Dee8gonator 1987 560SEC 196,000 miles - Sold
Orgasmatron - 2006 CLS500 90,000 miles
2002 C320 Wagon 122,000 miles
2016 AMG GTS 12,000 miles

Chad300TD- I dont have the owners manual so I cannot reference what was you are mentioning. Should I just turn the key, press on the gas three times and wait for the glow plug light to go out?

As for valve adjustments, can I do this myself or should I bring it to a mercedes mechanic?

Also what oil types would be recommended for this vehicle (both summer and winter, or both)? Should I be running synthetic only?

OK, first off, the light is just an indicator.
the glow plugs will stay on for 32 seconds after you turn the key. you should be able to hear the relay click off. I would turn the key, wait until the relay clicks off, then turn the key off and back on and wait another 30 seconds, THEN put the pedal to the down about 1/4 the way, then turn and hold the key in the start position until the motor outruns the starter. once it starts, if it runs rough, you have a plug or two (or more) out. a light tester only checks to see if the glow plugs are getting voltage. you need a digital ohm meter. www.dieselgiant.com has a mercedes help page with detailed instructions for testing the glow plugs.
post some pictures on photobucket.com and link them here. lets see your new baby!
http://www.dieselgiant.com/mercedes_diesel_maintenance_tips.htm
http://www.dieselgiant.com/glowplugrepair.htm
http://www.dieselgiant.com/mercedesblockheaterinstall.htm

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John HAUL AWAY, OR CRUSHED CARS!!! HELP ME keep the cars out of the crusher! A/C Thread
"as I ride with my a/c on... I have fond memories of sweaty oily saturdays and spewing R12 into the air. THANKS for all you do!

My drivers:
1987 190D 2.5Turbo
1987 190D 2.5Turbo
1987 190D 2.5-5SPEED!!!

1987 300TD
1987 300TD
1994GMC 2500 6.5Turbo truck... I had to put the ladder somewhere!

I just checked the weather reports for Buffalo and Clifton Park. Looks like your lows are about the same as mine. My '83 has a nearly identical engine and glow plug system to your '85, and with recently adjusted valves, good-working glow plug system, and 5W40 synthetic in the pan, it starts up easily in any weather. I just turn the key to run, wait for the glow plug light to go out (and another second or two while I finish putting my seat belt on) and crank. Maybe give it a little extra fuel when it starts to catch, and that usually does it.

I'm not sure what procedure you used to test your glow plugs, but a bench test is best. This requires pulling the plug and supplying it with 12V and watching it. It should be glowing (literally) in a few seconds.

Valve adjustments aren't terribly difficult if you have the special wrenches, which are available from this site. They aren't cheap, but compared to shop labor rates they will pay for themselves in one or two jobs.

As for oil, any diesel-rated 5W40 should be fine. I'm still running 15W40 (and loop glow plugs) in my other car, and it starts, but not easily.

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Whoever said there's nothing more expensive than a cheap Mercedes never had a cheap Jaguar.

83 300D Turbo with manual conversion, early W126 vented front rotors and H4 headlights 400,xxx miles
08 Suzuki GSX-R600 M4 Slip-on 22,xxx miles
88 Jaguar XJS V12 94,xxx miles. Work in progress.