86 300SDL smoking and missing when cold
 

I have to admit I am new to the forum with regard to asking questions. I have used information off the forum multiple times for quite a while. At the moment I am flummoxed with this car. I replaced my 84 300DT with this unit about 7 months ago having purchased it from the original owner with all repair records....Texas car in fact.

So after driving it back to Michigan I decided to do some routine maintenance that had not been done in about 100K. The injectors and glow plugs were replaced as well as the ERG valve which was hanging up. The glow plug relay and circuit are working fine and all the other EDS systems were tested and work fine. But it still smokes and would idle with a miss until about the 50 C temperature line. From there is runs like a champ. I just finished a 1500 mile trip with an average of just at 30 mpg. Before the trip, since I hate that darn smoke, I ran a bottle of diesel purge through the system and installed new filters. The clear bottle I used showed the recycling diesel purge as being nice and clean.

Welp, the smoking and missing are worse.....but it still runs very smooth when warm. The missing has gone from say once per 12 firings to once in 5 to 7 firings. I would have to say the "diesel rattle" at idle is worse sounding as well. The only thing that makes sense at this time is that the IP needs to be replaced. It has 187K on it...as does the car. But that is a lot of money and work if that is not the problem. So I turn to the group of experts for assistance. I hope someone has the answer or has experienced the same problem with some ideas of solutions.

It's unlikely that the IP is the culprit.

One injector with a bad pattern can cause a misfire when cold. The warmer engine will tolerate the bad pattern and still manage to use the fuel and produce power...........the cold engine won't.

I trust that you allow 20-30 seconds of glow time until you start it...........correct? If you use the light as your guide, most 603's won't have a clean start unless they have afterglow.

Sounds like delivery valves.

Also have the new injectors tested, most are not up to spec.

Yes, the glow plugs are kept on before starting. New injectors not having the correct pattern is really not something I was considering. So cracking each injector line and seeing if a particular one makes no difference would give me a clue.

Retarded IP timing will cause smoke and misfiring when cold.

Hey now, let's not be mean and call names. That's challenged IP timing.

Check the timing chain stretch
 

I had a similar problem and I was positive that air was somehow getting sucked into the fuel system and it was especially noticeable when cold. Turned out to be timing chain stretch of about 10 deg. When I replaced the timing chain, the "missing" problem disappeared.

i dont disbelieve that it could be a timing chain but i dont see how it would not be as noticable as engine temp increased

Warm engines are less sensitive to the timing being off. The 603 is picky they really need to be right on.

Ain't ignorance bliss??
 

Welp, after a nice meeting with Mr Hunter at a Park and Ride, the issue is #6....either the injector or the prechamber. Considering this started after installing reman injectors from Bosch with now 8K on them, the prechamber probably is not the culprit. The ignorance is that after 5 Mercedes diesels, I have never heard hammering like this before. Not a sound I will forget again for sure.

With some Googling of MB injectors, I find that a company in India is advertising that they make all the Bosch components and I have no idea just how anal they are about the quality of their products. I know darn well how the Germans are so I find myself baffled over an injector that is junk after 8K miles. Not that the germans do not make mistakes....but usually those mistakes are due to over engineering, not the quality of the steel.

So, some new injectors, checking the prechamber and the IP timing and I will report more.

OK,

I just fixed my 300sdl. Had bad-bad smoke at start and a knock at idle that was unbelievable, and an intermitent miss about every second or two at speed.

I got the car given to me by my ex sis in law (they love me) they said it had smoked and knocked for years and about 200k miles. They just thought that is how diesels sound.

I went thru all the same things you are doing. Found the problem, bent connecting rod #6 cyl. Could have hydrauliced on fuel or someone may have ethered it.

Seen lots of Kubota, Ford, you name it tractors destroyed with a dollar can of ether.

Dave

I saw your thread about the bent rod. Obviously keeping my fingers crossed. However, it runs extremely smoothly when warm with no misses or flutters so based on your info, I am thinking the rod is not bent. We shall see!!

The problem is that most Bosch injectors are made in India. They are the crap ones that cause these problems. Remove your injectors and have a Bosch shop test them and fix whats wrong. Chances are only a couple of them need attention.