It was 15 degrees here in Nashville, NC last night. I had just refueled. I also added a gallon of Kerosene to keep fuel from Jelling. We've got an ice storm coming! Well, I forgot to plug in the block heater this morning and when I went to go to work, she sounded like she would fire on the first bit of fuel and then I let off the key. I let the plugs cycle again and nothing. Five times nothing. The battery sounded like it was getting a workout. So I plugged up the heater and got a ride. When I got back home, she fired no problem. I think my fuel jelled.

There's a first time for everything. She has started fine every other cold morning before this tank without the block heater.

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1982 300SD Light Blue
2002 Honda Accord SE
1974 Toro Wheel Horse Tractor
2000 Toyota Tundra Pickup

hmmm, I wouldn't think gelling would be a concern until somewhere below zero.

What is the official "gel point" of diesel?

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1987 300TDT
1981 VW MKI Caddy 1.6 diesel, waiting on engine swap
1983 D-50 Power Ram 4x4 "Mitsubishi" 2.3 turbo diesel
assorted gas powered crap and motorcycles

RIP: 1984 300TDT, 1982 300TDT, 1984 190D 2.2, 1992 300D 2.5, 1987 300TDT, 1982 Maxima LD28, 1983 Maxima LD28, Isuzu C223 P'ups X3, 1983 Holiday Rambler 6.2 Banks turbo diesel, 1984 Winnebago LeSharo 2.1 TD, 1985 Allegro 6.5

Plugging the block heater in is not going to do anything for the fuel line. There is a separate heater for the fuel line that you can install but unless the next ice age is upon us you should never reach a low enough temp in NC to have to worry about it. This is the advice from Marshall Booth on cold starting a diesel. Pay particular attention to the last paragraph:

Cold Starting a Diesel

An MB diesel should start with no block heater above 0F. Below that you'll need a block heater. MB recommends 4 hours for 0 - 32F and all night for below 0F.
Check list (if I've missed something anybody is WELCOME to add their two cents worth):

Valves MUST be properly adjusted (must not be even a tad "tight" and not grossly loose).

Glow plugs must all be working optimally and must be energized for a sufficiently long time to properly heat the prechambers (this may require glowing 10-20 seconds AFTER the dash light extinguishes - especially if there is carbon accumulation in the prechamber or the plugs have started to fatigue).

Battery MUST be fully charged and have sufficiently low internal resistance to deliver the needed glow plug and starter current. Conventional lead-acid batteries more then 5 years old are seldom reliable (and many fail sooner, though that has NOT been my experience with Interstate and Johnson Controls manufactured Die Hard batteries). Batteries that have been maintained exceptionally carefully and special construction batteries like the Optima MAY last longer, but I have a lot less experience with that then with conventional lead/acid batteries maintained rather normally!

Fuel must be properly treated for temperature to minimize clouding and be free of water. Filters must have full and not marginal flow. The fuel system must be free of any leaks (and this includes the hand pump - if it leaks when you pump it - it MUST be replaced).

Oil must not restrict cranking speed (either a "lighter" weight conventional oil or synthetic is HIGHLY desirable for prompt starting).

After an appropriate preglow period, press the accelerator pedal to the floor (to move the rack away from the "stop" position) and as you start cranking, release the pedal to about 1/2-1/3 and do not stop cranking until the engine starts and is running evenly! You may only get one shot at this and you need to play ALL of your best cards the very first time.

Marshall Booth

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Bill Reimels
Now down to one:
1972 300SE 3.5 W109 (Euro delivery)

Marshall is right of course.

With many of the 617's you only get one chance to start them.

If you let go of the key too soon, and the engine does not continue to run, additional attempts may result in failure.

My theory on this is the fact that there is too much cold wet fuel in the combustion chamber and the cylinder cannot generate enough heat to fire it all off, so, you get nothing. Has happened to me before, as well.

That being said, I do not understand Marshall's suggestion to plant your foot on the floor prior to turning the key. The engine cannot use any more fuel than it can possible burn at idle. Giving it too much fuel, in a valiant attempt to start it, is a recipe for failure, IMHO.

My '81D 300D that does not sit in the garage at night did not start up at 19dF just recently. I had to drive the 300SD that sits in the garage. First time I have never had one start. I suspect the compression is probably not at 400psi.

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Jim

I thought one advantage of diesels is that they are relatively insensitive to the mixture ratio. To much fuel might cause a lot of blue smoke but I didn't think it would be responsible for the engine not starting. Of course I could be wrong, it's happened once in the past....I think....

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Bill Reimels
Now down to one:
1972 300SE 3.5 W109 (Euro delivery)

You are correct, Bill. The mixture ratio is not the issue. All diesels typically have much more air than they could possibly need.

The issue is temperature and heat. You start off with a stone cold combustion chamber which absorbs heat like a sponge. You must get the fuel above ignition temperature, in spite of this hugh cast iron heat sink.

Now, you inject fuel into the cylinder. The fuel, being somewhat liquid, also must be heated up to ignition temperature. Liquids suck up a tremendous amount of heat to raise their temperatures. Any liquid in the cylinder adds to the misery of trying to attain combustion temperature.

If you add too much fuel in there, there is no possibility of getting all that fuel up to ignition temperature and firing it off in a reasonable amount of time.

Reasonable is defined as the length of time your battery will provide to you for full cranking speed.

Personally, I would think it would be benefical to crank the engine for 5-6 seconds without any fuel (rack fully shut off). This would serve to rapidly increase the temperature in the cylinder because there is no liquid to heat up. Then, add a little fuel and light it off. I'd like to see someone who has starting issues with an older 617 try this approach. Of course, you would need to connect a separate Mityvac to the vacuum shutoff to attempt it.

On the issue of how much throttle, if you check the operation of the IP you will see that it doesn't matter where the throttle is because when starting it will provide the same amount of fuel. The difference comes after you have started the engine, more throttle will get the engine up to an rpm that can be maintained, quicker.

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1977 300D Lost coolant while someone else was driving
1983 300D Can't run without oil
1985 300SD (gone but not forgotten)
1990 300TE 4matic Sold
1991 Yamaha Venture
1975 Kawsaki 250 triple
1974 Honda 200CL
1951 8N Ford
2008 Wildfire 650C

#1. Valve adjustment.
#2. New glow plugs.
#3. New starter.
#4. Compression test.

My 1985 300SD starts first time every time at -6F without the block heater...

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ASE Master Mechanic
https://whunter.carrd.co/

Prototype R&D/testing:
Thermal & Aerodynamic System Engineering (TASE) Senior vehicle instrumentation technician.
Noise Vibration and Harshness (NVH).
Dynamometer.
Heat exchanger durability.
HV-A/C Climate Control.
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Technical Quality Auditor.
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1985 300SD
1983 300D
2003 Volvo V70

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yea - I keep forgetting the glow plugs.
I've changed them on two "customers" cars over the past couple months.

I'll change the gp's over the next few days and look to see the last time I did a valve adjustment. I have just recently gone to running 20% biod but that should not make any difference. I guess this is a good indication it needs a little attention.

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Jim

[QUOTE=engatwork]
I have just recently gone to running 20% biod but that should not make any difference. QUOTE]
Yes it will. Even though the percentage is low it still acts as a cleanser and loosen up all the dino crap that has been acumulating all over the tank walls and fuel lines, pump ect. You may be experiencing filter clog to some degree.
First place to look is the fuel tanks screen sediment filter (inside the tank on Benz's) and then the other filters as well.
Are you making your own BD or buying commercial ? Has it been properly washed ? These things are important when dealing with the first couple tank fills of biodiesel.
It's too cold up here right now for it, but as soon as it warms up to over 5-7C (mid 40'sF) I am back to 100 % biodiesel homebrewed. I can hardly wait.
Luc

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1983 240D 4 speed running on B100 and SVO
www.b100wh.com/b100wh.html#reactor
My Biodiesel Reactor/Processor

Right now I'm running store bought. I knew it would loosen up the debris in the tank. I has not been 6 months since I dropped the tank screen and cleaned it up. I'm sure it is a matter of time before I have to do it again.
I still think I probably need a new set of glow plugs.

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Jim