Hello all new here and I bought a 1985 300d trying to learn about these cars. I bought it about a month ago and it started right up every time, but the last few days it has gotten harder to start when it is cold. I have done some research which leads me to think a problem with glow plugs.
One question I can seem to find the answer to is how long the glow plugs are supposed to glow for. My glow light stays on for about 30 seconds every time weather the car is hot or cold.
Thank you for listening.

It should glow for about 10-15 seconds. You could try glowing two cycles before starting up and if the engine starts easier that would indicate you probably need to replace glow plugs.

There's a write-up for testing at dieselgiant at Mercedes Diesel Glow Plug Repair

The first part with the multimeter will tell you which ones if any are bad. Some people just replace the ones that are bad and other people just replace all of them. It's a bit of labor but not too bad to DIY. If you pay a mechanic, you should have all of them changed.

Dkr.

Thirty seconds sounds about right but it could be shorter; I will count mine tomorrow. If it is below freezing there, then change to some lighter weight oil. I think I have 5W30 in my 300SD now. The lighter weight oil makes a lot of difference in how fast your engine will turn over when starting. Start with the simplest fix and then move forward.

Welcome to the Mercedes diesel world and this forum. You will find a great many people here who are willing to help you.

You are exactly where I was 2 years ago. I bought a well-worn 1985 300D.

You will learn a great many things quickly, but one of the first things that you should determine is if your car is a California model or a Federal model. This will only affect a few things, but it is a difference that will crop-up. The major differences (there many be others):

• Intake manifold
• Exhaust manifold
• EGR connections
• Turbocharger mounting (the actual turbo is the same, just mounted differently)
• Air cleaner-location, housing and filter element
• Some transmission details

Most likely, you have a Federal model which has an engine bay that looks like the attached picture (I forget which member supplied this photo). Note the location of the air cleaner.

Strangely enough, I don't have a similar picture for my car, but the air cleaner will be much taller and lives right behind the passenger-side headlight.

None of this applies to your glow plug questions; I just wanted to welcome you and warn you of a possible variation.

Attached Thumbnails

 

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Mike Frederick
1986 300SDL, 240K+ miles
1985 300D KaliKar, 270K+ miles

You might also want to update your forum information (use the User CP link on the left side of the forum "tabs") to let us know where you are located, etc.

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Mike Frederick
1986 300SDL, 240K+ miles
1985 300D KaliKar, 270K+ miles

Welcome to the best automotive forum on the 'net (my opinion). I have a few upgrades to offer for the '85 cars with CA emissions, as well as products to make your A/C work better (all 617 & 616 engines).....Rich

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All Diesel Fleet
1985 R107 300SLD TURBODIESEL
2005 E320 CDI (daily)

LOTS of parts for sale!


EGR block kit
http://www.peachparts.com/shopforum/diesel-discussion/355250-sale-egr-delete-block-off-plate-kit.html

1985 CA emissions 617 owners- You Need This!
Sanden style A/C Compressor Mounting Kit for your 616/ 617 For Sale + Install Inst.

Sanden Instalation Guide (post 11):
http://www.peachparts.com/shopforum/diesel-discussion/367883-sanden-retrofit-installation-guide.html

I did not spell check the below.
What is the Glow Plug Light doing when you turn the Key to the Preglow Position.

The Glow Plug Relay has a Temp Sensor inside and the Glow Plug Light goes out when that Sensor considers you have preglowed long enought to start the Car. However, I think that works well if your Engine is close to the new engine specs. Otherwise you have to do what is needed to get the Engine to start.

The Glow Plug Light is merly a prompt for the Driver. If you ignore the Glow Plug Light and keep the Key in the Preglow Position the Glow Plugs will remain on until the Timer in the Relay turns them off. As the others have indicated the total time the Relay can stay on before it times out is about 30 Seconds.

If you want to start again with another 30 seconds of preglowing you need to cycle that Key off and back to the preglow position.

Your Glow Plugs are also on while your Starter is Cranking.

If during the Preglow your Glow Plug Light blinks and after the Engine is started the Glow Plug Light goes on it is an idication there is a problem in the Glow Plug System.

This is not a recommend to buy parts there but on the Diesel Giant Website there is a good pictorial on how to do a quick Check of the Glow Plugs with an Volt/Ohm Meter. The Meters are cheap and Harbor Freight Stores.

If you remove the Glow Pluts the carbon should be reamed or otherwise cleaned out of the holes. How to do that and what to use is in the Repair Links.
For more extensive info see the Repair Links.
Fast navigation http://www.peachparts.com/shopforum/diy-links-parts-category/146034-fast-navigation-do-yourself-links.html

Note the Valves on Your Engine needs periodic adjusting. Prior Owners seldom pay someone to do that and seldom have the skill to do it themselves. If the Valves are not properly adjusted it effects starting.

Switching to Synthetic Oil allows the Engine to spin faster during a cold Start.

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84 300D, 82 Volvo 244Gl Diesel

Sounds like the system is working perfectly. What temperatures are you doing this starting in, and how is the strength of your battery? A strong battery is essential to cold, and old diesels starting.

How many miles on the car ?

When was the last time the valves were adjusted ?

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Greg
2012 S350 BlueTEC 4Matic
2007 ML 320 CDI
2007 Leisure Travel Serenity
2006 Sprinter 432k
2005 E320 CDI
1998 SLK230 (teal)
1998 SLK230 (silver)
1996 E300D 99k, 30k on WVO
Previous:
1983 240D, on WVO
1982 300D, on WVO
1983 300CD, on WVO
1986 300SDL 237k, 25k on WVO (Deerslayer)
1991 350SDL 249k, 56k on WVO - Retired to a car spa in Phoenix
1983 380 SEC w/603 diesel, 8k on WVO
1996 E300D 351k, 177k on WVO

Thank you all for the replies. I am in the DFW TX area. I will finish profile. Its been about 50 or so here. There were colder mornings when the car started easier.
So in my 30 second relay is kicking on on the plugs does that mean they are getting hot?
The light stays on for the full 30 seconds then I can here the relay click. I did come across diesel gaint and will test the plugs asap. When cold the car seems to smoke more the when warm.
Just for peice of mind my dad and I did a compression test the last weekend and all 5 cylinders where about 420 psi from my understanding that's great.
Actual miles of car unknown the odometer quit working at 196k valves were adjusted about 2 weeks ago
The battery was another question I had. The guy I bought the car from put a nee battery in it and its like a group 27 with 800cca would putting the proper size group 49 in the car make a difference?

My OM617 is in a race-only S-10 pickup so my experiences may not apply too well to your situation but I have started "going around the block" with this engine.

My glow plugs are hooked up to a Ford-style starter solenoid instead of the Mercedes timer system. If I hold my button down for about 10 seconds it always fires right up but as a race truck it's always in the shop at probably 50 degrees F or warmer. I hooked this system up and tried it and because it worked OK I haven't checked the plugs - I'm thinking they're OK, though.

I'm not tootin' my own horn but if you want to see this engine stripped to it's basics you might want to peruse my build thread. The S-10 is basically a rolling engine test stand for the engine so you can see a lot of the basics without all the stuff that's on a production car.

Hope this is helpful.

Dan

Glow relay problems are very common in our old Mercedes. It is a very sophisticated design for a glow relay but sophiscation means more parts that can fail with age.

It sounds like your glow light is not operating as designed. It should time out and go off before you hear the click. What's important is whether the glow plugs are getting power. Connect a test light across a glow plug and you'll be able to see instantly whether they are getting power or not.

You may want to consider going manual glow if it continues to give you problems, it is one of the best thing I have done to my 85 300D. I make it easy with my modded OE glow relay. It bypasses all of the electronics and connects the glow light directly across the glow plugs. One wire to a momentary push button switch to +12 V is all you need to install. Everything else is stock, same mounting , same connectors- plug and play.

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85 300D turbo pristine w 157k when purchased 161K now
83 300 D turbo 297K runs great. SOLD!
83 240D 4 spd manual- parted out then junked

That is kinda what I thought I shouldn't be hearing the relay click. Sounds to me that my plugs aren't getting hot if the relay is kicking them off after 30 seconds

Glow relay should click on when you turn the key to on, it should click off after a set time that is determined by a temp sensor inside the glow relay. The glow light is independent of the click off and should go off before the click off.

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85 300D turbo pristine w 157k when purchased 161K now
83 300 D turbo 297K runs great. SOLD!
83 240D 4 spd manual- parted out then junked

If the temp is only 50 F then heavy weight oil is not your problem. Should start to about freezing temps with regular weight oil. Valve adjustment sounds like a good solution too.