Cold Starts - PeachParts Mercedes-Benz Forum

armkb · #1 01-07-2008, 11:34 PM

Have a 1984 SD with 209k miles, runs strong, decent fuel mileage. My problem is anything below 15 degrees and it just wont start. Ive replaced the glow plugs, adjusted the valves, new battery, checked all battery connections, put a heater in the lower radiator hose, use 5w-40 Schaeffers synthetic oil and it just wont start. Turns over well but just wont fire.

Had the same problem last year but this year I thought that the block heater would do the trick but it to has not helped. Do you think its just that the engine is somewhat down on compression due to the age and mileage and with the cold air and fuel combination that it just isnt getting enough heat in the combustion chamber to fire?

Also considered changing the starter and adding another battery as I thought maybe it really isnt turning over as fast as it should. Does anybody have any suggestions on what my next possible step should be. Have I covered all the bases?

Hatterasguy · #2 01-07-2008, 11:57 PM

Have you checked the timing?

How about the compression?

raslaje · #3 01-08-2008, 12:27 AM

Are you using a winter fuel blend?

http://answers.yahoo.com/question/index?qid=20070120193310AAQ523I

Rmcfarland · #4 01-08-2008, 12:40 AM

I just recently went through virtually the same deal as you and replaced almost those exact parts. And, I also had no success firing once it got very cold out.

My problem turned out to be my fuel (filters, perhaps). The little clear primary filter was running dry of fuel for reasons unknown when cranking. I think I may have a bad filter(s), or a tank vacuum, or a leak. I am not sure just yet. I zip-tied the primary filter in an upright position so all the available fuel would run to the bottom (and therefore into the injector pump). I have had no bad starts since. Once it is not butt-freezing outside I will do more thorough investigations.

Now, I am not saying this is your problem, as I believe mine is a bit of an isolated case. But the fuel system certainly is suspect when cranking seems good and GP's are in working order.

My engine burns a fair amount of oil with a fair amount of blow-by, so it is safe to say that my compression isn't optimal. But it fires well now, even in the cold. Just a couple of cranks before fire now. What I am trying to say is, I think these engines will still fire pretty good even if they are a little tired, if everything else is OK.

I'm sorry, this is a rambling post even for me. Keep plugging away at it, You'll find out what it is eventually.

*edit* Forgot to add, I am using no block heater now. I may once it starts having more difficulty if it gets colder.

kerry · #5 01-08-2008, 08:50 AM

I'd do a compression test to get a clear picture of what is happening.
However, if it starts at higher temperatures, it should start at 15 with a block heater. Are you sure your block heater is working? Have you put an infrared thermometer on the block after running the heater for a few hours? How long are you running the block heater before attempting to start the car?

mobetta · #6 01-08-2008, 09:47 AM

lower hose heaters aren't known to work the best, but some peeeps seem to get along with them just fine.

If you are slightly mechanically inclined, you can get a diesel compression tester @ harborfreight for $25, and do your own test. that will tell a lot about engine condition.

armkb · #7 01-08-2008, 09:33 PM

No I have not had a chance to check the timing, planned on changing out the timing chain in the spring due to the high mileage. No have not checked the compression yet.

We do have winter blended fuel and I do add Schaeffers Diesel Treat 2000 plus additional Amsoil Cetane Booster hoping it would help with the starting.

I have recently changed out the fuel filters within the last 5k miles or so and I can see in the clear filter that the fuel isnt gelling as its quite fluid at the low temperatures.

I know the inline block heater isnt the best choice but I have left it on for over 3 hours at a time and the front of the cylinder head is warm and the thermostat housing is hot so I know its working. I will have to check again and see if the rear of the cylinder head is getting warm or not.

My engine doesnt seem to burn much oil as I only add about a pint or so between oil changes and the blow-by doesnt seem excessive, as I dont get much build up in the air cleaner housing. Blow-by and additional oil between changes has definitely decreased since using synthetic oil.

I too also have a feeling its fuel related, although I have no data to back it up.

Diesel911 · #8 01-10-2008, 01:32 AM

Quote:

Originally Posted by Rmcfarland

I just recently went through virtually the same deal as you and replaced almost those exact parts. And, I also had no success firing once it got very cold out.

My problem turned out to be my fuel (filters, perhaps). The little clear primary filter was running dry of fuel for reasons unknown when cranking. I think I may have a bad filter(s), or a tank vacuum, or a leak. I am not sure just yet. I zip-tied the primary filter in an upright position so all the available fuel would run to the bottom (and therefore into the injector pump). I have had no bad starts since. Once it is not butt-freezing outside I will do more thorough investigations.

Now, I am not saying this is your problem, as I believe mine is a bit of an isolated case. But the fuel system certainly is suspect when cranking seems good and GP's are in working order.

My engine burns a fair amount of oil with a fair amount of blow-by, so it is safe to say that my compression isn't optimal. But it fires well now, even in the cold. Just a couple of cranks before fire now. What I am trying to say is, I think these engines will still fire pretty good even if they are a little tired, if everything else is OK.

I'm sorry, this is a rambling post even for me. Keep plugging away at it, You'll find out what it is eventually.

*edit* Forgot to add, I am using no block heater now. I may once it starts having more difficulty if it gets colder.

If there was a fuel supply problem the injection pump similar to the one above I am wondering if pumping the primer pump a dozen times or more before you start the car might be a way to test for that. Maybe there is an air leak or the fuel supply pump is has worn or gummed up valves. I think if you give it a good priming and it starts easily this could be a good indicator as to where the problem is.

whunter · #9 01-10-2008, 02:13 AM

Quote:

Originally Posted by armkb

Have a 1984 SD with 209k miles, runs strong, decent fuel mileage. My problem is anything below 15 degrees and it just wont start. Ive replaced the glow plugs, adjusted the valves, new battery, checked all battery connections, put a heater in the lower radiator hose, use 5w-40 Schaeffers synthetic oil and it just wont start. Turns over well but just wont fire.

Had the same problem last year but this year I thought that the block heater would do the trick but it to has not helped. Do you think its just that the engine is somewhat down on compression due to the age and mileage and with the cold air and fuel combination that it just isnt getting enough heat in the combustion chamber to fire?

Also considered changing the starter and adding another battery as I thought maybe it really isnt turning over as fast as it should. Does anybody have any suggestions on what my next possible step should be. Have I covered all the bases?

Please check your PM.

Have a great day.

junqueyardjim · #10 01-10-2008, 11:26 AM

My 300 d Turbo was a bit hard to start at 15 degree F. So just before Christmas I changed the oil and went with the new Mobil truck and Turbo synthetic, 5 - 40 on the label. I am totally amazed the starting difference. Now at 15 F it starts like it does in the summer. It seems like a totally different engine. Oil consumption might be up just a little. I think I will have to add a quart at 3000 miles. I sure recommend giving it a try if you are having starting problems.

rrgrassi · #11 01-10-2008, 12:01 PM

If the starter is not spinning the engine fast enough, it can also lead to cold start issues. Only problem is that I do not know what RPM is "fast enough". On my 300D, the tach reads about 250 to 300 rpm, but who knows how accurate that is.

Some people give 2 -3 glow cycle before cranking the engine in cold weather.

mdesmarais14 · #12 01-10-2008, 03:35 PM

I too was having cold starting issues even at 25 degrees. Then I changed my oil to 5W-40 Rotella Synthetic, (will try the Mobil 1 Turbo Diesel Truck oil next) and it is like a totally different car. Last week it got down to -4 in MA, and the next morning at a balmy 5 degrees it started right up, after one full glow cycle. The starter def has a much easier time with the new oil....

MB-Owner-in-ind · #13 01-10-2008, 04:17 PM

Quote:

Originally Posted by mdesmarais14

I too was having cold starting issues even at 25 degrees. Then I changed my oil to 5W-40 Rotella Synthetic, (will try the Mobil 1 Turbo Diesel Truck oil next) and it is like a totally different car. Last week it got down to -4 in MA, and the next morning at a balmy 5 degrees it started right up, after one full glow cycle. The starter def has a much easier time with the new oil....

This is my results also.