96 300d... how cold is too cold?
 

Welp... after much ado getting new glow plugs installed in my 96 E300D, I figured it was ready for anything. Drove it to work yesterday... started just fine (block heater plugged in), then when my wife went to use the car at lunch, she had a heck of a time starting it (temp in the mid teens) and got a battery charge warning. She finally got it started, drove it a few miles, then parked it at work again. When 4 pm rolled around, the car started just fine.

Today, we went into town (started just fine again) and the car sat until 4 pm again. I was the one to try to start it this time... NO GO! Cranked--rested--cranked--rested for several minutes... got the battery charge light, so flagged down a jump start (mid teens again BTW.) After several attempts, the beast finally started. Not good for the battery, I suspect!!!

I was worried that I had a frozen fuel line or something, but once it started, it ran just fine.

'leads to the BIG QUESTION: How cold is too cold to drive this car if it's not plugged in? It seemed to do fine when the temp was above 30F... but getting stranded when it weather is in the mid teens is not my idea of a good time.

At what temp should I consider driving a gas burner?

Thanks in advance!

-l-

How old is your battery? Have you had it tested? Perhaps your alternator isn't charging the battery properly? Unless you're running SVO or biodiesel, these should start in very low temps (assuming decent engine compression) I have an 83 300D with only 4 out of 5 working glow plugs and I have never had an issue starting it in even the coldest Michigan weather ( Yes, it misses for a bit)

How old are the injectors?

I have a 1999 E300. It starts as well in the low teens and the thirties.

I just started my diesel in 2 degree weather yesterday. Something must be wrong with your car such as glow plugs. Also i did not have the block heater on.

Also, fuel quality can make a big difference.
Filters?

Hi , I have a 240 d with about 260k on the odo. This morning when I first started my car it was 9F outside. My car is parked outdoors, not pluged in. I bought the car last year in Texas, about this time of the year and imidiatly had starting problems when the weather dipped into the teens. (I live in Kansas) A simple oil change to mobil 1 5W20 made starting much easyer. Also check your battery, Is it the proper battery, and in good condition? Also, starters will loose torque with old age. nothing a good rebuilding wont cure. Just because the starter turns the motor dosent meen that it is fast enough.
So number one, Change oil to a low viscosity oil , two if your battery is old get a new one, also check your charging system to make sure it is preforming properly. (the battery place can do this)If these items are in good order thats the most common problems.
I have rebuilt my starter and the car turns over faster now, but for me it was the oil and battery that did the trick.
Jon J
1981 240D
260K

Have you considered adding a small amount of petrol to the tank (say 5% or less) to reduce any gelling?

I would try several, make that dozens of other options before I added gasoline to the fuel in that car. Winterized diesel should not be gelling at that temperature.

For a point of reference, my 1996 E300D has been starting fine in the negative single digits we have had in Chicago for the past few weeks.

I have a '95 E300D and haven't had any troubles with cold starts. The other day it was about 10* outside and it fired right up after one glow of the plugs. When it gets real cold I will often glow the plugs twice just for kicks, probably don't need to, but I figure it can't really hurt anything.

The first thing you should do is check tha battery. If your battery is even borderline, temps that cold can suck the life out of it. And if the battery gets drained and freezes, then situation gets even worse. If you can, take the car to one of the many parts chain stores and have them test the battery and alternator. If that checks out okay, then check your plugs.

I am really loving my block heater this winter, but not for getting the car stated - rather, just for getting it warm so I can take off down the road quicker. Good luck.

ditto on checking the battery.

this morning we started right up at -8°F (outside, not plugged in).

...and the original question is a trick one - at no temperature should you consider trading it for a gasser.

I'd look for air in a fuel line. Was it parked nose up in town perchance?

Terry, as usual, has a good point. I changed out my prefilter a couple of months ago and the new o-rings that came with it was not sealing it up properly. Took it for a drive down the road, stopped somewhere, got back in a few minutes later and nothing - wouldn't turn over. On top of that, I subsequently killed the battery (which must have been on it's way out) trying to get started. Double bummer! One new o-ring and one new battery later and everyone was happy again.

Whew... I'll try to answer all the comments so far (THANK YOU!!!)...

First, I don't know how old the battery is. It is was with the car when I purchased it in Houston this summer. I guess what I don't understand (with regards to the battery) is... if it cranked (and cranked... and cranked) shouldn't that allude to the battery being OK? The car cranks... sometimes sputters, then cranks (no sputter.) It is not as if the car only cranked 3 or 4 times then the battery charge light came on. Am I missing something? Also, I should note I just changed all glow plugs last week, so I'm hoping that is not the issue (again!)

As far as fuel goes, I been adding the Powerstop additive to prevent gelling. I'm thinking that if gelling were the issue, it wouldn't have started at all, regardless as to the amount of cranking.

Oil is Rotella synthetic (5w-40 is the weight or is it 5w-30?)

As for the parking of the car in town. It is at a slight incline (perhaps 2 degrees.)

Once the car was started, it ran perfectly...

Dunno...

THanks!

-l-

Oops... forgot to mention... don't know the age of injectors... I'm assuming the same age of the car. Also, I was told (by the prior owner) that the fuel filter had just been changed (that would have been at 134K.) Don't know if this car has a pre-filter... I do have a new main filter on the shelf though.

-l-

Well, if the battery is discharged to certain extent, then you might have enough juice to crank, but not to start. It is possible that the cold temps are pushing the limits of you CCAs (cold cranking amps) and your battery might be starting to show its age. I would just drop by a parts chain and ask them to test it out for you. Then you will know for sure. Also, you should be able to check the date on the battery to see how old it is. You can check out this link for some good battery info - it starts out basic, but builds up to some insigtful battery trivia.

http://www.autoshop101.com/autoshop16.html

Just click on the links for "Battery Basics" and "Battery Services"

I am thinking that the clear fuel lines need to be replaced. The O rings are probably weak and there is just enough resistance with the fuel that its sucking in air.

Same year and model with 204,000, and like you I recently changed out all the glow plugs. Car sits outside, no heater, and has started with no problems in 10 degree temps with 15-20 mile per hour winds. I would suspect that you may have a fuel issue that is causing the erratic issues you describe. I think you stated that you changed out the main filter, but there is also a pre-filter right next to it that can cause major issues if its o ring is not installed properly, or has failed. I would start from the the basics, and work up from there. From other posts I have read, the K-40 relay also seems to be an issue with erratic starting behavior in this year and model. Good luck with you problem.

Dug the battery out this morning and will have it tested this afternoon. I still don't make the connection with the battery (no pun intended.) I also think it may be a fuel problem... but why only when it gets below a certain temp?

The previous owner had changed out the fuel lines so that he could run biodiesel (though I don't think he ever did.) I suppose I could replace the fuel lines again if you think that would help... are they pretty generic? Also, I will take a look for a pre-filter. When I first bought the car, I ordered a full filter assortment... only saw the fuel filter... no pre-filter.

I take it a K-40 relay is related to fuel supply?

My 96 with 83000 miles won't start if I haven't plugged it in when the temp goes below 40!
The red and green lights under the mirror start to alternately flash and the check electronics message comes on.
I tested it with an OBDII but it said NO Codes.
I changed out the K40 but that didn't help.
I've been using Castrol 20-50 in both cars and the 87 starts just fine no matter the temp without being plugged in.
Car runs great otherwise.

Sounds like a glow plug issue... mine did the same (other than the flashing lights on the mirror) when I lost a plug. Actually... I think the car had a plug out when I bought it as one cylinder made a racket when it started until things warmed up. Since replacing the plugs, the car (when not too cold outside) starts beautifully and runs quietly.

Read a bit on the K-40... as I haven't had any issues with the car stalling out, I question if this is the issue.

-l-

Look for air, and try parking nose downhill in town to make starting easier.

As someone else said, you do have a pre-filter. Its oring is often the probelm.

Is located on the left side of the fuel filter housing as you face the engine compartment. A fuel line from the cyl head plugs into the top of it.

Thanks Terry... I just had Spokane Mercedes send me down a new filter and sealing ring. I guess I'll change out both filters and see if that helps. Any recommendations for purging air from the system?

-l-

I don't remember much about the winters in that area of the country, E.W. and W.I. fluffy snow IIRC,(I was 13 or so when I left Cheney...many many moons ago) but I doubt you would have many issues starting due to cold fuel there. battery? yes, starter? yes, fuel... doubtful. power service white should easily handle it.
did you test your glow plugs prior to installation? you could have a few bad ones out of the box... test them with ohm meter, and verify resistance is good.
a good MB battery should crank that motor for a full minute without slowing down. it's best with these motors to crank steady until they fire, but not more than 90 seconds at a time, with at least a 1 minute rest in between attempts.
several 20 or so second attempts will drain a battery fast.
once the motor is spinning, there is not really much strain on it. they are designed to handle heavy loads. it's the starting and stopping and starting that will wear them out, and drain a battery...

to sum up. -40°F/C is too cold for Diesel... however, it's too cold for gasoline too, and there ain't no good way to thin a gasser's fuel to get it going...
western Idaho rarely sees -5, so I wouldn't worry too much.

I just looked the weather averages for your winters... -27°F record in 1957... THAT would be a cold morning to try to start a diesel...

John,

I tested the plugs prior to installation... seemed fine.

I guess the problem I'm having with the battery theory is this: If the engine turns over at, what seems like the normal cranking speed, shouldn't the engine start (providing it is getting fuel?) I was cranking, oh, perhaps 30-40 seconds at a whack... was worried about that duration (but was looking at the option of being stuck in sub freezing weather 30+miles away from home)... so, 1 minute+ is acceptable?

-l-

You can view batt voltage on the CCu as you drive. Press and hold "rest" for 5 secs, then toggle using auto buttons to screen 24.

Suspect the cold weather and long cranking (which sounds like priming the fuel system) is responsible fore the dash light show.

All,

Well... the battery checks out to be in very good condition with "a lot of life" left in it... so I guess that nixes the bad battery theory. I believe Terry and co. is on the right track with regards to bubbles in the fuel system. I am looking forward to receiving the new prefilter/seal and changing both filters out. I still don't understand why the possible air bubble creates a problem with lower temps, but not high (can someone please explain this to me?)

The plan now is to change out the filters, then try starting the car at home (which is generally much colder than in town) some morning without using the block heater.

Also, if there is a proven method used to purge any bubbles in the system, I'd appreciate the "how to" on that as well.

THanks all!

-l-

Battery checks out - well, that is a good thing. As has been said, you can start it up and watch the clear fuel lines for awhile and see if you can actually see any bubbles being pulled through. Then, you might also shut it down and go back and watch the line again - if there is a leak somewhere it might suck some air back through after shutdown.

I can't explain why the temp might be an issue here. The problem is that there are always lots of variables in play, but which ones are actually involved can be difficult to diagnose - so sometimes it is just easier to think about the problem and possible causes of that particular problem. Here you are having erratic starting issues and, having been through the experience myself, it could be that the fuel lines are sucking air somewhere. If the lines are sucking enough air, you might notice it when accelarating on the highway - erratic fits of hesitation.

Nevertheless, I believe once you stop the engine some of the fuel eventually drains back to the tank (someone correct me if I am wrong here) and in the process, if there is a leak in the line somewhere it will pull air into the sytem - get enough air and you won't be able to start.

If you are changing out the prefilter, you want to pull the fuel line connector up out of the top of the prefilter. My point being that if you try to pull the prefilter out while the fuel line is still attached to it, you run the risk of damaging the fuel line - you'll see what I mean once you get at it. Also, before you attempt to change out the prefilter you will want to open the fuel cap to release some pressure off the system - it will help keep fuel from pouring out when you pull the prefilter. You can actually take a look at the area around the prefilter right now - start it up and have a look, then shut it down and have a look - you shouldn't see any fuel around the lip of the prefilter housing.

Finally, this system will purge itself of air (if it is not too much air) if you crank it enough. It would be a good idea to have some fuel on hand to fill up the prefilter housing once you change out the filter. It holds very little fuel in there, but every little bit helps. Once you have it all back together, crank it for awhile to try and purge any air - I would say not longer than 30-45 seconds, then give the starter a couple minutes to cool down before trying again.

Good luck!

I think I may have found the problem here. I took a look at the filters and such and noticed that there is a small bit of diesel down around the fuel preheater. I'm wondering if it is possible that when the temp drops below a certain point, there is enough contraction on that unit to cause some leakage. Anybody know if tightening the bolts holding the preheater to the block have any effect on diesel leakage, or would that just have the effect of keeping coolant from leaving the block?

BTW-- the car started immediately this morning after sitting in the barn (level) all night, albeit it didn't drop below 20 last night.


UPDATE...

Just went out and ran the car... definitely bubbles between the preheater and the prefilter (looks like the flippin' Mr. Bubble factory!) Anyone have a diagram of parts in this area? I'm heading down to tear off the manifold once again and see if there's anything obvious leading to/from the preheater.



Thanks!

-l-

OK... I took the manifold off and discovered that the black hose that leads from the firewall to the preheater was leaking at the connection to the preheater. I cut off ~12mm and reconnected. I no longer have a hooka effect (i.e. there is no bubble steam in the clear tubing between the preheater and the prefilter.) However, once I turn the car off, there is a bubble that forms at the prefilter and moves back along the clear tubing towards the preheater. Is this due to a leaky seal at the prefilter? I'm guessing this is the case but as my parts haven't arrive from Spokane yet, I will be quivering with anticipation...

Thanks for the tip on this!

-l-

That bubble is perfectly normal at shutdown.

I suspect the hard starts were due to parking nose up allowing air in and fuel to drain back to the tank through the leaky line.

The reason to park nose down if you suspect a leak is to prevent, or slow, air from entering.

Ahh....
 

Good to hear I may have this licked. Thanks Terry for the insight to look for air leakage. Also for clarifying why parking nose down might help relieve the "cold no-start woes"!

Also, thanks to the brother Tankowner for the link to the battery site! I've always been curious about some aspects of batteries (which the site cleared up for me.)

I'll probably postpone filter changes until the snow stops flying (unless need dictates otherwise.)

I'll keep you posted.

Thanks all, once again you've saved my sorry butt from a visit to a "professional" (and the large bill that usually accompanies said visit.)

-l-

I have doubts as to the validity of those little battery-tester-on-a-cart devices.

They are probably calibrated to the range of batteries that is sufficient to start the average Honda that shows up wanting a battery check. The batteries our diesels take to crank are several times larger, and also need to be several times stronger to get a heavier diesel going and keep it cranking until it's running.

They may be wide-range tests, I don't know - but a battery could test out a-ok, I think, start a Honda for three more years, and fail to start one of these diesels.

I have wondered frequently why M-B didn't take a lesson from John Deere and run two batteries in these cars. They could have found room. (I'm not talking about a 24v system, I'm talking about two 12v batteries working together to last twice as long (give or take) on those hardest emergency cranks. Wired parallel, not series.