Mixing gas w/diesel for cold start?

[Arkansawyer]

In spite of new glow plugs, my 1985 300D will not start when the temp drops to around 20 degrees F overnight. Block heater is out of the question as I live off-grid. My buddy who drives a VW Rabbit says that VW recommends mixing up to 25% gasoline in the wintertime. I'm wondering if this will work on my Benz? I sure don't want to do it if it will damage the engine or fuel system. Anybody got any input on this? Thanks.....Dave

[79Mercy]

It was about 32 here the other day and my 76 300D started up 1st try and only took 2 turns of the motor. Check those glowplugs again and make sure all 5 are working and also check the relay.

[okyoureabeast]

Originally Posted by Arkansawyer

In spite of new glow plugs, my 1985 300D will not start when the temp drops to around 20 degrees F overnight. Block heater is out of the question as I live off-grid. My buddy who drives a VW Rabbit says that VW recommends mixing up to 25% gasoline in the wintertime. I'm wondering if this will work on my Benz? I sure don't want to do it if it will damage the engine or fuel system. Anybody got any input on this? Thanks.....Dave

I drive an 85 as well and I had the absolute pleasure of trying to start my car with a sub zero temperature at 2 am.
I'm going to cut and paste what I wrote in a thread over at benzworld. I doubt gelling diesel is your problem.

My 300D has been having an impressive ability starting cold. I'm very happy with the results.

Here are a couple of tricks I have picked up from searching.

1. Do a full glow cycle well after the light turns off. You'll hear a distinctive click. It's about 45 seconds. Use your watch because it does seem like an eternity.

2. Adjust your valves. This will help greatly with compression. Do a compression test and see if you have any low compression.

3. My car doesn't have a block heater, but I read on peachparts of a guy who boiled water and dumped it over the engine block. After that he could crank the car. Yours does have a block heater so doing this is kinda pointless.

4. Are your glow plugs all fully working and getting power? If you're having issues starting that cold it may be glow plug related among other things.

5. Last resort: WD-40 the intake a bit and crank. Your car will stutter and puff, but it should get it going.

Good luck man. Those are really the only things needed to get our w123s going!

[ashedd]

I just did a valve adjustment on my TD for the first time. A whole different car! Starts right up without all that smoke it once had. I also bought a new battery. Glow plugs tested fine but I did pull them and ream.

So do a valve adjustment

[thebenzbar]

Originally Posted by Arkansawyer

My buddy who drives a VW Rabbit says that VW recommends mixing up to 25% gasoline in the wintertime. I'm wondering if this will work on my Benz? I sure don't want to do it if it will damage the engine or fuel system. Anybody got any input on this? Thanks.....Dave

I remember years ago in PA when an MB tech advised NOT to do this on my 300TD... because of risks and detrimental effects. Fuel pump or injection failures were some of the problems he encountered. Combustion temps get raised and cetane rating lowers as well, and I'm sure there are other reasons against it... so in the end, I wouldn't risk it IMO.

[Sbean]

Merecedes owner's manuals (Mine's from 1980) used to suggests adding up to 50% kerosene or up to 30% regular unleaded gasoline in very cold temperatures, if #1 diesel was not available. I don't know when they stopped recommending it. Steve

[thebenzbar]

Originally Posted by Sbean

Merecedes owner's manuals (Mine's from 1980) used to suggests adding up to 50% kerosene or up to 30% regular unleaded gasoline in very cold temperatures, if #1 diesel was not available. I don't know when they stopped recommending it. Steve

I heard the "very cold temperatures" recommendation was based on -10 degrees Fahrenheit which equates to approx -23 degrees Celsius
Obviously to combat against the extreme cold temp's gelling effect.
At these frigid temps, battery and glow plugs must be 100% up to snuff at a minimum.

[strelnik]

Originally Posted by Sbean

Merecedes owner's manuals (Mine's from 1980) used to suggests adding up to 50% kerosene or up to 30% regular unleaded gasoline in very cold temperatures, if #1 diesel was not available. I don't know when they stopped recommending it. Steve

about 1973, when the fuel started lubricating the fuel injection pump directly. Besides the intent was never more than about 10% by volume MAX.

[vstech]

Originally Posted by strelnik

about 1973, when the fuel started lubricating the fuel injection pump directly. Besides the intent was never more than about 10% by volume MAX.

my 1982 owners manual states to mix gasoline with diesel fuel in subzero temps if gelling causes problems and if kerosene isn't available.

[leathermang]

Originally Posted by strelnik

about 1973, when the fuel started lubricating the fuel injection pump directly. Besides the intent was never more than about 10% by volume MAX.

Where did you GET that ?

Since my 1980 owners manual quotes a higher percentage of gas allowed to be mixed with the diesel in cold weather... I would like some kind of reference from some kind of Mercedes literature.... otherwise it looks like you made it up. You know, some people do those kinds of things...
Show us you got that somewhere legit....

[nckmsn]

If never heard so many weird explanations. I have seen many diesel mercedes not start in 20 degree weather. A bloack heater always solves this problem.

I think we need more information about the subject vehicle. Perhaps the motor is owearing out. Who knows. I think we need to hear back from the guy asking the question.

I do agree that everything needs to be tuned up including the valves, but I also think that these motors with a lot of miles will have trouble starting in 20 degree weather even with everything tuned up.

[strelnik]

Originally Posted by leathermang

Where did you GET that ?

Since my 1980 owners manual quotes a higher percentage of gas allowed to be mixed with the diesel in cold weather... I would like some kind of reference from some kind of Mercedes literature.... otherwise it looks like you made it up. You know, some people do those kinds of things...
Show us you got that somewhere legit....

Read through some of the papers from SAE on diesel lubrication and on the Cummins service books. They tell you that IPs that have forced engine or internal lubrication systems can handle the lack of lubrication caused by the mix of modern unleaded gas with low sulfur diesel, whereas, in the case of the newer vehicles which use diesel fuel as a lubricant/coolant, this can cause wear ovewr the long-term.

This is the same reason 40 years ago that MB in the old ponton diesel owner'smanuals for the OM 636 and OM 621 diesels, told people not to mix gas too often because high-octane Benzin also contained vanadium additives which were bad for injection pump machined surfaces.

I'll go home and give you threference.

I used 1973, because I thought that was the last year that the IPs with independent lube systems were used like in the 220D. If I'm wrong there, I'll admit it.

[Jeremy5848]

I guess this is one of the challenges of living off-grid that hasn't been in the press. One thing you can do is to remove the battery and take it inside so it stays warm until you need it to start the car. Batteries lose much of their power when they are cold.

[kerry]

20 degrees is not cold enough to cause fuel problems. Do some more checking on your glow plugs and if they check out, do a compression test. 20 degrees should not be a problem on a relatively healthy engine with functioning glow plugs.

['83 240D]

I live off grid too and in North Dakota so my diesels have had to be started on some really cold mornings with no block heaters.
What works for me is to make absolutely sure all glow plugs are working perfectly, engine is tuned perfectly, valves etc, battery is the highest capacity I can fit under the hood and when it's really cold I keep it in the house until I need to start the car. Synthetic oil has made a huge difference in cold starting as well. When I am away from home I just leave the car running, sometimes for days at a time but that's when it's well below zero. I have run my 500,000 mile 300SD at -58 below zero, with almost -90 below zero wind chills, the secret to starting it when it's that cold is to start a fire under the oil pan. In my garage I have a pit for oil changes etc, and I have a wood stove down in the pit so when I want to go somewhere I go out with an armload of kindling or sticks and start a really hot fire in the stove, which is directly under the car when it's parked in the garage, in about 20 minutes I can run the defroster without even starting the car and of course, with the engine plenty warm it starts just like a summer day. For when I am not parked in the garage I have one of those propane weed burner torches that I keep handy, light this and carefully place under the engine so it doesn't melt any electrical or rubber parts, in about 10 minutes both the oil and the engine are warm enough to start perfectly, even at -20 below zero and an added benefit is the transmission gets a bit of heat too. I have used gasoline in the diesel mix to keep the fuel from jelling but I prefer mixing kerosine. Usually I just run #1 fuel with an additive for lubricating.