I have a 1980 240D with about 211K on it. I just noticed at high RPM’s, right before I shift gears, there is a ‘pinging’ or engine knock coming from the engine. There is no knocking/pinging any other time – even at idle and moderate acceleration. As you know, the 240D does run very high rpm’s when traveling on the highway and therefore the pinging is noticeable on the highway now. Any ideas?

Background info: I have been running WVO for about 2000 miles – greasecar system w/fattywagon injection line heaters. I also adjusted the valves about 500 miles ago, however, I just started to notice this problem a couple of days ago. I use Shell Rotella 15W-40 oil. Car runs fine otherwise and does not smoke.

Do you think I should run some diesel fuel cleaner in the diesel tank? Or maybe I should try adding some type of oil additive in the engine? Please advise.

 

you condition sounds like at higher rpm the injectors are nailing due to them not being able to close off fast enough probably due to some buidup of deposits. I have recently done a diesel purge on my car 187k on it and to say the results was amazing is an understatment. Nailing stopped completely, idle is quieter and milage is better. Advice i received from a diesel mechanic was run two cans through and then add about 8 oz of clean diesel to insure all the purge is out of the fuel filter. then change all filters. You will not believe the old filter on how dirty the oil pours out of it.

 

Where can I get diesel purge? How do you do the purge?

 

purge is Lubro Moly, buy it on the internet, cost about 8 bucks or so a can,, you want diesel purge,,
how to do it there are various articles, this is one link to use, http://www.mindspring.com/~houlihan/merc/repairs.htm or you can use this link, both say same thing, unhook fuel in, and unhook recirc line back to fuel tank,,, and place in jug, fill jug with purge and rock and roll

http://dieselgiant.com/mercedes_dies...nance_tips.htm

 

Thanks for the info.

I did the diesel purge tonight and it seems to have cleared up most of the nailing, however, I can still here it very faintlly at just the right speed. Between 40mph and 50 mph, if I let off the accelerator just right I here what sounds like some knocking/nailing. I did the 2 cans of purge just like diesel giant says. I did notice that my fuel purge bottle was completely BLACK of re-circulating fuel. I guess it worked...maybe just not as good as I had hoped. Idling, highway driving, and accleeration are great. Any other suggestions? Do you think I should just drive it the way it is and not worry about it?

Thanks for your help.

 

I would not worry about it,, if it was that dirty you might have to do it again, i can not say since i can not hear it.
did you change the fuel filters afterwoods?
a slight nailing sound is nothing to worry about, though considering that you reported the same as i did, i brought my car back to the mechanic that recomended i do the purge and he said it sounded better, that you can not get it to completely stop sometimes since the injectors might be worn a little and not sealing exactly,,, if it bothers you i would try to purge it one more time and do not forget to add about 8 oz of diesel to the purge container when it is almost down to make sure all the product is gone, but if you do it you will have to change your filters again.
also, what is the cetane rating yo are using?? the higher the cetane the easier to ignite, so maybe that might be part of the problem,,, i doubt it but would be intrested in knowing what yo have in your car

 

Try some biodiesel in the tank. if there is any crude left (in the tank, in the injectors, fuel lines) it will clean it out. But you'll need to change the filters angain soon if you do


Higgins