She is running a bit rough on idle
 

In my '76 300D I have noticed a bit more nailing, on idle lately, so I replaced the return lines hoping that I might have a small leak. I replaced all the lines except the plug on the last injector; I will have to do it later when I get one. Anyway, she is still nailing a bit and still a bit noisy on idle compared to when I got her a few months ago.

What else could be causing the excessive noise? Injectors firing early?

-Scott


Had to edit the poor diesel terminology... nailing not pinging.

300d4me

I don't think leaking return lines would cause nailing, I would run a can or two of Molly Purge through then find a hill and do an Italian tune up. Use the search as you will find plenty on nailing, its a common thing, Do you do allot of city driving?

Make sure your vacuum pump diaphram is not defective, letting excessive oil get into the intake manifold. Remove the line going from vacuum pump to intake manifold and make sure no black engine oil in line or at fitting on vacuum pump----black oil means leaking diaphram. If diaphram leaks bad enough, you will also notice "hard" brakes and more smoke than usual from exhaust.

300d4me,

My 1975 240D was very susceptible to poor quality fuel and it was while driving that car that I was introduced to RedLine Diesel Fuel Catalyst. Made the "nailing" and clatter at low power/very slight throttle position while coasting or backing off go away. Try the Moly Diesel Purge stuff, and then use an additive with every fill up to make up for some of the poor quality fuel you run into. Should help, and if you are lucky like I was, makes the problem go away. Good luck, Jim

I generally put in an additive with every fill, either Redline or Lubro Molly, depending on the feeling of the day. I have a can of Molly Purge and I will have to see if I can run it through this weekend. I am assuming that an Italian tune up entails a lead foot up the hill?

I do a lot of city driving compared to the highway travel I do.

I think I read some ware that injectors need to be replaced or rebuilt every 100k or so. Is that correct? I am about to start breaking her in, I should turn 200k real soon. I think the article I read blamed the majority of nailing during idle on wore injectors.

-Scott

300d4me

I think you have a good chance of clearing up your problem with the Italian tune up and Molley Purge but it may take a while. I put new nozzels on my injectors for about $25.00 ea, its a no brainer job and I figure I will clean the old ones and keep them for spairs. 100K sounds reasonable to me although how you drive and the quality of fuel makes a big differance.

Ya, you got it "lead foot up the hill" Load the engine good but dont lug it .

Steve