January 3, 2015

Baby it's (too) Cold Outside... for my G-Wagon

Living in Park City it can get cold so that classic great American song holds true here. We actually love the cold here because this is a ski town and our economy is based on folks wanting to ski on hundreds of inches of snow. That being said the weather is usually pretty good with bright sunny days and highs in the mid 20's to low 30's and with the low humidity, it is very nice in the winter. But once in a while, we get those arctic blasts and the temps can go very low. That is exactly what happened last week when the temp dropped below -12 F. 

My G-Wagon is a 1984 280GE who's previous owner had a 300CD turbo engine put in it. The G-Series of that era could be purchased with the OM617 engine, but none were made with the turbo option until the 90's. But Mercedes-Benz did fit some of the sedans of that period with the OM617 Turbo, an engine that still has a cult following today.

The problem is, at -12 F the 280 dual overhead cam gas engine would fire right up. I know this because we have a 1984 280 SL and as long as the coolant and oil are correct for low temps, no problems starting the car in the winter. Not so much with the diesel, as it has no spark plug to ignite the fuel. Diesel ignites from heat generated when it gets compressed. Glow plugs help, but when it is very cold, the fuel just does not get hot enough so... no combustion.  

I'm not new to diesel as my Kubota tractor has a 3 cylinder diesel and while it is hard to start when very cold, as long as I keep a winter blend of fuel and add a little winter treatment I don't have trouble with fuel gelling. Even then, on the coldest mornings, the tractor is very hard to start.

That is why I was surprised when I had trouble starting the G-Wagon when it was parked outside overnight. When keeping it in the garage heated at 50 there is no problem, but when parked outside overnight and the temp goes below 20, it is nearly impossible to start. Last week, when it dropped below 0, there was no way it would start. I had to tow it into the garage with the tractor and let it sit overnight, only then did it crank up. Yes, the tractor started but the Mercedes would not!

I checked the glow plugs with cables and all are reading .7 OHMs. That is a shame because Bosch 80006 Duraterm plugs are only about $10 each -- that would have been on an easy fix. I also checked the relay and am getting 11V on each of the five wires leading to the plugs and it correctly drops to 3V after the initial warm up. Additionally, the glow plug relay was even staying on longer when it is very cold. To bad because I can fix just about any electrical problem

I was beginning to think my plan to use a diesel as a winter car was a mistake. If you ask my wife she will say it WAS a mistake. When I started looking for a G-Wagon I wanted the peppier 280 anyway so now I'm feeling like the 280 would have been a better choice. I was not ready to give up!

Convinced the car was working as it should, I started looking for an engine block heater. For those of you who are not used to being in very cold climates, engine block heaters warm the engine block by either heating the oil or the coolant for easier starts, shorter warm-ups and less friction on the engine. 

Zerostart Engine Block Heater
The OM617 engines shipped to the states were fitted with an integrated engine block heater. So I looked under the exhaust manifold where the OM617 should have the heating element and all I found was a large plug. No heating element. I guess the California cars including my engine donor did not get the heaters.

Mercedes owners are used to great parts availability and you can get a OEM Part #: 606-200-00-94 or 900-203-48-95 for about $120. Turns out there is also an aftermarket unit called the Zerostart PN 310-0105 Engine Block Heater that fits most older Mercedes-Benz engines and you can get it from Amazon for about $45. 

Glow Plug Reamer
Before installing the block heater there were two things I did to make the engine run better that just happen to make a big difference with the cold starting issue:

First I removed the old glow plugs and reamed the chambers. This sounds easy, but took some time. You will need to remove the wire nut from the old glow plug, remove the old glow plug, install and remove the reamer until it does not bind, vacuum out the hole, clean, lubricate and replace the glow plugs. There was quite a bit of carbon build up in the chambers because the reamer was hard to get in the first time. The build up had to dramatically reduce the effectiveness of the glow plugs.

The second thing I did a diesel purge to further clean the carbon from the entire fuel system, including the prechamber. I did this to clean the fuel system and deliver more power. CLICK HERE for detailed instructions on the purge process. 

Those two easy steps helped the car start better in the cold and so far the car starts with no issues even when it is in the low 20's. I'll do a test on the next extreme cold night and report the results. 

Back to the block heater because even though it does start in the cold now, I know there will be those crazy cold days and a preheated engine will start with less wear and tear on engine components even when it is not Arctic cold. 

I attempted to remove the plug to install the block heater. I treated the area around the plug with a penetrating lubricant in advance. Then I put a 19MM hex socket on a 1/2 driver and even with a long pipe could not get the plug loose. Since the reamer and the diesel purge improved things so much, I decided the block heater could wait.  

Update 11/12/15 it was 17 degrees this morning and I forgot to put the cold weather treatment in the G-Wagon. I left it outside overnight and after two tries, it started right up. I believe the diesel purge and the reaming (cleaning) of the prechambers where the glow plugs are installed made the difference. After this latest test, I'm no longer worried about the cold winter of Park City... baby - it's not too cold for my G-Wagon and I've become quite happy with the 300G Turbo

1 comment:

  1. I will certainly do the two procedures when I bring mine home. While the Northeast winter is not as brutally cold as yours, the ease of cold starting is a concern in my mind when I was deciding to buy the 300GD or not. Again, thanks for sharing.

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