606 miss when below 0 degrees
 

Hello I have been lurking for some time now. I have a 1997 with the OM606. I have had other Mercedes diesels in the past. The car has 110K on the ticker. On days below zero it bucks and snorts and smokes like a detroit diesel. At this same time it will not rev past 2 grand. All fuel lines have been replaced and the injectors are new. Glow plugs are all new and read approximately 1.6 ohms each. A few minutes into this event it will start to act normal. I am at a loss as to why but it did set a CEL last time it did this. I am not sure if this was due to an undervoltage condition to get it to start. It acts like there is air somewhere that is being purged, but I am thinking EGR for some reason. I have cleaned the intake, flaps, and have a new switchover valve. Any thoughts from the group.

Do you have a block heater? Give that a shot. I don't now anything about a om606, but it sounds like once your engine picks up a little heat it starts working right. Below 0 is cold for a diesel to start without help. Also, try cycling the glow plugs 2 or 3 times before starting, that help my old vw friend.

Your injectors may need a good cleaning too. If the fuel isn't atomizing properly, it'll have a real tough time firing at those low temps. Have you ever cleaned/had them cleaned?

Are we talking Celsius or Fahrenheit here?

Either way, it should make no difference - the engine should start normally. Germany can be a pretty cold place, as can Scandinavia.

When was the last time you changed the fuel filters? Maybe there some water in the main (can) filter causing you problems. Also, maybe its the fuel itself? Are you burning standard diesel or bio? Adding any anti-gel to it? I use the power service white bottle in the winter - it helps disperse water, stops gelling and adds a few cetane numbers too. Sounds to me like you have a fuel issue based upon what you have already done.

Fahrenheit is the temperature. Fuel filter is new, and I always use Stanadyne or Power service fuel treatment. I do not use biodiesel. Could compression be suffering? I make sure that at these temps that I use Rotella T 5-40 synthetic oil. Maybe it is just a downfall of an indirect injected engine.

Don't cycle the glow plugs like people recommend or do on the older diesels. Go through your normal sequence, but when the glow plug light goes off, don't do anything different. The glow plugs are still glowing and getting hotter. They glow up until 180 seconds or so, (you'll know when the glow plug relay kicks off as the dash lights get a little brighter :-) ). I usually waited at least another 20 seconds or so, I seriously counted 20 seconds prior to cranking, giving ample time for things to warm up prior to firing. Mine usually fired up without an issue, but it would and does nail like hell when it's that cold. My last winter prior to moving down South :-)

Mine will fire within the first few revolutions after glowing so long. In those temps you'll waste more battery energy cranking the engine longer, rather than glowing a little longer prior to cranking. I'll never forget, the last time my car was in those temps it was either 4 or -4 fahrenheit on the digital cluster. I let it glow around as long as I stated and it fired on the second revolution and came to life. Wooooom Woooooom, clank clank clank clank :-)



Regarding the sputtering, etc... I would say it could be in relation to the injectors ... i.e. calibration, etc....

NO NO to the Stanadyne. It's a good additive, but I believe it's still an emulsifier, it will separate the water from the fuel. The full flow filters are the only "water separators" on these diesels. Best to use an additive that has demulsification properties as our diesels do not have a water separator. I have been using the Redline Diesel Fuel Catalyst, which addresses this. Here is link to the Technical Information on this additive. I know Advance Auto Parts used to stock it but the one near me doesn't anymore.

RED LINE® DIESEL FUEL CATALYST with CETANE BOOSTER and FUEL LUBRICANT TECHNICAL INFORMATION

I have started my '98 after parking out overnight in below zero (F) weather with nothing more than the usual glow cycle (wait for the light to go out) and turn the key.

It never takes any more cranking than when it is 70 out. One or two revs with the starter and it starts. No shaking or bucking. If all was correct with yours it would not shake or buck either so there is something wrong here. I still suspect fuel or the additive you use. How long has it done this for? Do you always buy fuel at the same station?

They do nail a bit when cold, that is normal...they are also noticeably slower until they warm up a bit - also normal, but missing or smoking or bucking is abnormal.

Have you tried reading the OBDII for stored codes? You say it threw a CEL one time - I don't suppose you scanned it then?

Have you closely examined the top of the injector pump for diesel leaks? Any sign of leaks there would indicate bad delivery valve seals. Also, when was the last time you replaced the o-rings on the shutoff valve and prefilter? These are the three most often overlooked causes of performance/fuel system issues.

Before I fixed my #6 glowplug, the car would buck, knock and emit clouds of bluish-white smoke on cold start up. Now it starts instantly (coldest so far this year is 10 deg.) and purrs like a kitten until the plugs de-energize. After that, it gets a little noisier but still within normal parameters.

I wonder if you have at least one weak plug that's not working well enough to help with combustion but not malfunctioning badly enough to set a code...

I would say from your discription that one or more of your glow plugs are not lighting up. I have a 96 E300d, and my car exhibited the exact same traits that yours is showing, only in my case, the "Glow Plug" light would come on after the engine was started, indicating one or more of the plugs were bad. The ohm reading test is not always 100% accurate, and even though a plug gives a low reading, it may not be functioning as designed. I replaced all six plugs, and the issues dissapeared immediately. If it is air in the lines, then the same traits that it exhibits at zero should also be present at warmer temperatures. If the car set a CEL, it would be helpful to know what the number of the error code was in order to try and narrow down the problem. Good luck!!

Would seem to me that this is the problem unless the resistance of your meter itself reads 1 ohm.....New they should be .6 to 1.0.

Was the carbon reamed out when they were replaced?

I have mentioned this several times, but it might be worth mentioning again. When doing the glow plug resistance test, do a before and after glow test. That way you'll know for sure they're all working. The resistance should be much higher when they're hot (on my meter it shows as a high negative number that's dropping).

>>(on my meter it shows as a high negative number that's dropping).

DieselAddict, that is an excellent suggestion. Thank you for describing it.

I've been thinking on and off for ages about how you might cheaply and simply be sure that a glow plug is actually glowing properly and getting hot without having to go to the bother (and risk on an OM606!) of taking it out.

What you see on the meter is, of course, the glow plug behaving as a thermocouple, and producing a small voltage in reaction to the heat (as per the milli-volt method described by Barry1234) - hence your meter reads a changing resistance as it cools - absolutely brilliant!
Top banana! :vbac47679

Glad to help. I thought of this long time ago when I was curious whether it made any difference in the ohm reading if the plugs were cold or hot. Then I saw the dropping resistance values as the plugs were cooling and I thought that actually made sense. More heat = more resistance.