'78 300D Injector R&R

I have two injectors that leak and am getting ready to replace them. Any hints as to how to do it? Parts store I where I bought injectors sold me parts that require taking off the top part of the injector.(i.e. overflow & fuel line end) Is this right? Also, what size deep socket is used for the injector, 29 or 29mm?

This is my first posting and I wanted to thank you all for the good tips I've already picked up just watching!

The injector takes a 27MM deep socket.

All you have to do is take off the injection pump to injector plumbing (I call it the spider) and remove the injectors.

Cautions:

Be careful to see that everything stays clean and dry. I usually place the spider and injectors into a plastic bag, and throw a clean rag over the pump.

Be careful when actually lifting the injector out of the hole, you can lose the seal ring very easily. If there are no seal rings in place, get some, they are very cheap. They go in with the largest end of the taper toward the bottom.

Unless the soft return lines have been replaced very recently, get a stick of this tubing and renew it when you put everything back together. If this tubing is old, it most likely will not seal when put back in place.


Are they leaking around the base, or are the injectors themselves leaking? I've never seen the injector leak. I've seen fuel around the base due to seals not being in place, and I've seen the soft return lines leak and dribble fuel down the side of the injector.

Good luck,

Thanks Larry!

I think it is the injector that is leaking. I've replased the return hoses first and no-go. The leaks appear to be where the injector (?) screws into the 27mm part which screws into the head.

Now, the part I have is the injector nozzle. Is it a harry pain to take the injector apart to replace the nozzle? This parts supplier is 20 feet from a shop that specializes in MB repairs and this is what they do. They also replace it in the car. I guess its time to invest in the engine manual!

I've never taken apart an injector. It may not be difficult. The important thing will be to do this in an extremely clean and dry area.

Best of luck,

Thanks again! I'll let you know how it turns out after this weekend!

[Douglas Broome]

Be sure to replace the spacers with new ones below the actual injectors. Frakly, I has seen so many people have trouble with home rebuilding injectors that I simply get already rebuilt ones. The come from my purveyor at about $50 each, or less. What is the cost of the parts when you rebuild them?

Douglas:

Not counting the Hat seal (which I didn't replace) it cost $81.00 for two injector nozzle inserts plus one meter of hose for the return lines so that's $40.50 per injector. It wasn't hard, just dirty and messy. The hardest part was cleaning the carbon and gunk from the injector once I had it apart. Now, I'm not so sure I have all the air purged from the system.
Like a dumby, i didn't print out the thread on purging air that i had read a week or so ago. Because, when I went to p[rint it before i pulled the injectors, it had removed, of course :-( That'll larn me!! I don't have any leaks from those injectors but it still starts hard, so, if it isn't air or leaking injectors, i guess it's timing. Tha means i go in search of more tools to adjust start of delivery.

[can-do]

Greetings Panzer,

You've got me curious as to why you rebuilt the injectors if you say the leak was between the injector and the prechamber cup. Was fuel sort of bubbling out of the threaded prechamber area or actually out of the injector itself? I had that problem myself but changed out all the injector heat shields and that put a stop to it. Also in your thread you mentioned that the injectors where carboned up and dirty. Was that on the inside of the injector that all the dirt and carbon was found? Please shed some light on what you found so a few of us can learn what crude may be lurking on the inside of our injectors. Did you have a performance problem as well as a leak, and after replacing parts and cleaning the rest, was there a performance difference or did it just rid you of this fuel leak? Got me wondering now.

Charles

Hold your horses here!
Did you set up the opening pressures after you installed the new nozzles? If not, you did no benefit to the engine, the opening pressures MUST be reset with new nozzles (by a shop with a $1000 hand pump). You adjust the pressures with the shims (varying thickness). Yes, the injectors are known to leak between the halves, very common on rebuilt injectors. Also, without proper opening pressures the injector may leak internally into the engine.
Not to upset you, but you paid ALOT for an injector nozzle. They are available up here at a diesel injection shop for $35 CDN each, rebuilt injectors run $60 CDN each complete.
Greg

[Douglas Broome]

The last post is why I suggested simply going with rebuilt injectors form your friendly parts supplier. Also, since you have replaced the hose between the injectors, be sure to replace the end capped piece after the last injector, closest to the firewall. They have been known to crap out. They are cheap.

Can-do first, The leak was coming from the between the injector halves. The leak from the injector/pre-chamber collar was afterwards. (replaced the heat shield?/nozzle plate) The Injector face was carboned up but also the injector insert andthe inside of the nozzle. I didn't have a performance problem that i could tell, I've only had this 300d for 4 months. Also, my other car is a Diesel Jetta which the Fiat 126 (2 cyl) I drove in Italy had better performance. (almost):-)

Clacker, jsut what I wanted to hear! The price I pay for having it locally! Not much in the way of diesel let alone Benz parts in Northern Va.

Doug,
Next time I'll go for the whole enchilada! By the time I joined the group and started this thread, I had bought the nozzles and was ignorant of opening pressures and such! Will have to check with the local MB shop on costs of a tune-up for this puppy.

By the way, what will the engine manual for a '78 300D cost me? The Haynes manual is ok for some of the basics but is a little lacking!

Thanks,

[Douglas Broome]

Is Panzer in Northern Virginia? I am as well. I have a very good (read cheap) local source for most M-B parts. Contact me if you want this source.

Douglas:

I tried to send you an e-mail about your part source but I guess I messed it up. I would like to get you source for parts.

[Eric Eliel]

For those of you just replacing your injectors for the first time, my '84 300D takes a 27mm deep socket. I was too cheap to spend the $29 for a Snap-On (how often do you think I'll need that 27mm?). I first went to Sears and brought one of the new injectors with me. The Craftsman 27mm deep socket is too short ($11.00). Only covers less than a 1/8" of the injector. Just for giggles I went down the street to Pep Boys (I thought they used to carry S-K brand tools). P/U a Performance Tool (made in Taiwan) 27mm socket for $5.00! Key Buy!