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1979 240D
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69 Posts
Discussion Starter #1
It's -15C here and I had my 240D plugged in all night. The coolant is nice and toasty, but the car just won't catch.

Can anyone recommend anything I can do to fix this issue, or alternatively, an engine rebuilder in the Toronto area?
 

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1985 300CD Turbo coupe, 2006 E320 CDI sedan
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573 Posts
Not much info to go on; like, is this your first diesel? - or is this your first winter with the car? If yes to either/both: did you use the glow plugs?

//greg//
 

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1979 240D
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69 Posts
Discussion Starter #3
The glow plugs are brand new pencil-style with an upgraded glow plug relay. I let the plugs glow for a minute, and cycled them three times. I'm not sure how I would even *not* use the glow plugs.

I did eventually get the car to start, but only after charging the battery and having the plug-in heater going for 8 hours. Clearly I am down on compression. The problem is that I can't always have access to plug the car in, I need it to be able to start anywhere.
 

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1985 300CD Turbo coupe, 2006 E320 CDI sedan
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I let the plugs glow for a minute, and cycled them three times. I'm not sure how I would even *not* use the glow plugs.
I don't understand. Isn't the glow plug indicator in your instrument cluster coming on? If yes - and you don't immediately turn the key to START once it goes out - the glow plugs cool down very quickly. If the glow plug light isn't coming on, they're not likely energizing at all. If that's the case, have you checked the fuse? I've attached a troubleshooting PDF that might help

//greg//
 

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1979 240D
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69 Posts
Discussion Starter #5
I rebuilt the glow plug system, I know how it works. The plugs stay on even after the light goes out, usually for 1-3 minutes depending on ambient temp. Once you hear the click from the relay, the plugs are off.

By cycling, I mean that I turn the key, the light comes on and then goes out, then the relay clicks a bit later, and I repeat this process three times to get the temp in the cylinder up as high as possible.

My point is that, even doing that, and having it plugged in overnight, it still wouldn't catch. I'm asking if there is anything else I can do to help the cold start situation, because I need to be able to get it started in the cold even when I'm not near a place to plug it in.

Alternatively, I was wondering about options to get the compression up in the engine - whether I need to do an engine rebuild.
 

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1985 300CD Turbo coupe, 2006 E320 CDI sedan
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So is this the first time you've tried to use the glow plug circuit since it was "rebuilt" ?

Sounds like you're talking about after-glow. I'll concede that I've never personally worked on an OM616, AND that my glow plug circuit is still configured the way it came from the factory. But what you describe is NOT the way it works on my OM617. If such a drastic difference exists between a '79 240D and an '85 300CD, I apologize for my ignorance.

//greg//
 

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1979 240D
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69 Posts
Discussion Starter #7
This is the upgraded relay kit, not the original system from 1979.

Some people are recommending throwing some kerosene in the tank, changing to a 0W30 oil and squirting WD-40 into the intake to get it rolling. Certainly better than rebuilding the engine if those techniques work.
 

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1985 300CD Turbo coupe, 2006 E320 CDI sedan
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This is the upgraded relay kit, not the original system from 1979.

Some people are recommending throwing some kerosene in the tank, changing to a 0W30 oil and squirting WD-40 into the intake to get it rolling. Certainly better than rebuilding the engine if those techniques work.
Yeah, but are you sure that's actually the way the upgrade kit works?

Anyway. My next oil change will be 0W40. Same cold viscosity as 0W30 for winter, but doesn't get as thin in the heat of the summer. But kerosene added to the tank is an anti-gel measure, don't rely on it to cure this issue. And if it's cold enough where the thing won't start normally, you may be disappointed in the WD40 advice.

Oil excepted, I think you need to forget the workarounds and get back to basics. You said you suspect compression. Have you even done a compression test?

//greg//
 

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1979 240D
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69 Posts
Discussion Starter #9
No test, but when the mechanic was setting the valves he said it was too easy to turn, indicating that the compression was down.

If indeed it's compression, it's about $6K to rebuild the engine, which is not a solution. So, workarounds will have to do.
 

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1985 300CD Turbo coupe, 2006 E320 CDI sedan
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No test, but when the mechanic was setting the valves he said it was too easy to turn, indicating that the compression was down.

If indeed it's compression, it's about $6K to rebuild the engine, which is not a solution. So, workarounds will have to do.
But he didn't actually perform a proper compression test - right? Were all the injectors sealed when he "discovered" this? All the glow plugs torqued in place? The valves closed on the "suspect" cylinder(s)?

If I had a mechanic who gave me a $6k quote for a 4 cylinder diesel rebuild, I'd find another mechanic. If for no other reason than a 2nd opinion. The results of a competent compression test might require nothing more than some new piston rings and/or cylinder liners.

//greg//
 

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1979 240D
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Discussion Starter #11
I called 3 different rebuilders and got similar price quotes from them all. And apparently no one does ring jobs anymore. At least none of the mechanics I talked to.
 

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Curious about mileage?

Also, have you considered potential fuel and/or fuel supply issues?
 

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1979 280CE
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6,118 Posts
Are you following the owners manual recommendations for starting that that temp? Push accelerator to floor 3 times, and then hold the accelerator at least 1/2 to 3/4 of the ways down while trying to crank the engine?

Also turn the idle knob up.
 

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try a new battery or starter

How fast does your engine crank. If not fast enough you may need to remove the battery and charge it over night. or replace it with a better one. This will also make your glow plugs hotter.


It could also be your starter dragging not letting it crank fast enough.

My battery works fine down to 10 f any lower and it starts to fail fast.
 

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82' Euro 240D 84' 300D 01' SLK320 6 Speed Sport!
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315 Posts
While I am having similar issues this year with my 84' 300D, I can still cold start my 82' 240D with out plugging in and its been in the 20's. Some things to consider...adding "heet" in the red bottle to the fuel system, this really seemed to help, checking your starter, it may be getting "tired" and doesn't have that oomph anymore. Not sure about your glow plug mod, as it may be working against you, its hard to say if anyting on these cars is working 100%.
Good luck.
 

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87 Euro 560 SEL
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480 Posts
I would start at the beginning. Give the vehicle a COMPLETE tuneup and check the compression at the same time. And make sure you run seafoam or a diesel additive in the fuel. My wife's 82 300TD wouldn't start during our last -30C stint but she admitted she forgot to add seafoam to the fuel. Since then things have been okay.

Without a compression test you will always be second guessing. Without a complete tuneup you will also be second guessing. Water in a fuel filter, plugged air cleaner, tired oil will all give you hard starting issues. My 82 300TD has 3 fuel filters, for a reason. An issue with any one of them will cause hard starting. Start at the beginning. Oh and go out and buy PERFORMANCE Tuning & Repair by Mercedessource.com. EVERY MB Diesel owner has to have this inexpensive resource in the toolbox.

EDIT: I just reread Mercedessource PERFORMANCE Tuning & Repair manual. He has 5 pages dedicated to Cold Weather Starting. If you own a 123 Diesel you need this book.
 

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1979 240D
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69 Posts
Discussion Starter #18
The car had a complete tune up about a month ago - timing check, valves adjusted, all new filters, new starter, new battery.

I've since discovered that as long as I plug in the block heater when I get home, it starts fine in the morning even on -20C days. I guess the key is to get it while it's still hot.

I'll be putting in 0W30 oil and getting a boost box for the trunk, hopefully those two things will help if it's cold for extended periods.
 

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1985 300CD Turbo coupe, 2006 E320 CDI sedan
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I'll be putting in 0W30 oil
0W30 synthetics ain't cheap. But unless money is no object, I got a feelin' that - in the heat of next summer - you'll wish you went 0W40 from the gitgo

But I'm unsure what you mean "get it while it's hot". Am I to interpret that to mean you think the block heater needs to be plugged in while the engine's still hot? If yes, I'd replace the block heater. It's probably no longer putting out anywhere near the 500 watts that it was originally rated.

//greg//
 

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1979 240D
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Discussion Starter #20
Considering how much oil it burns and how down on power it feels, I can totally believe the compression isn't what it should be.

As for the block heater, it works well enough as-is and I don't mind plugging it in when I get home. So, why spend more money? I've already dropped more in repairs than I did in the purchase price so replacing parts that work "good enough" is low on my list.

I'll see what I can get in a 0W40.
 
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