Get a big mason jar and fill it with injector cleaner.

remove the injectors and soak them for about 8 hours.
get a can of carb cleaner with a little plastic straw and spray into each one from the fuel line side only. DO NOT try to clean the tips of the injectors as this end is very precise.
Check insulator sleeves for cracks as replace as required.
Re install them.
Works for me about every 25000 miles.

 

Isn't there a way to run the cleaner through the engine with the injectors installed? All the testimonials I read on SeaFoam mentioned huge amounts of smoke coming out of the exhause as testimonial to the gug that was being burned off.

On the subject of removing the injectors, though, I've already got a new set - 160k on my 420, and I don't know when/if these are original, I haven't been able to come up with a complete list of what other parts may/should be replaced. What I have are;
1. Injector
2. O-Ring
3. Injector Seals
4. Injector Insulator Bushings

That seemed like quite a lot of stuff to fit in the little valley of each injector ! LOL
3. But, I don't want to start the project until I have all at hand, since once I start I'll be w/out transportation until done.

Thanks again!

 

Well
You can run a can of seafoam in a full tank of gas. Pour it in then put the gas in to mix it. The "white smoke" thing is when you run it through a vacuum line into the intake system. I have seen people use the vacuum line off of the brake booster. I think that line is big enough. More theatrical than practical. This only cleans the intake not the fuel injectors. It does look cool though!! Seafoam mixed with the gasoline works better to clean the injectors. The method I mentioned prior is more thorough and complete but if you still want to use the car....
I assumed you may be having an idling issue or hesitation etc... hence the need to clean the injectors. If they are leaking then they are probably clogged or just plain worn out. Only a pressure test can really tell.
I have included some diagrams to assist you... It shows you what each injector assembly is comprised of.

 

I don't think there's much point in using the Seafoam if you're going to replace the injectors.

The pintle end is where injector problems occur. Deposits collect there and can hold the injector open or interfere with the spray pattern. The pintle and seat are similar to a valve and its seat in a cylinder head minus the valve guide. It's not what I'd call a precision fit.

I use an el cheapo Harbor Freight ultrasonic cleaner with seafoam as the solvent/cleaner. I use maybe three cycles after an overnight soak. After that I pressure test using a Bosch tester with Seafoam as the test fluid. If they don't pass the tests at that point they get tossed.

 

I started this whole thing because it's got really poor accelleration, and a lound pinging under load. I had it checked out, and they said it just needed the fuel mixture adjusted - that worked to reduce the pinging for a couple of days, but didn't effect the accelleration, and now the pinging is back.

So, that left fuel filter, injectors, and possibly the spark advance (?) - from what I've read in various threads here. I figured the injector would actually be marginally easier, since the fuel filter is tucked into such a tight place (although that is next on list after tank is less full).

I do have replacement injectors (I had thought if the SeaFoam cleaned out the ones already installed, then I'd just have a spare set). I'm not sure where to get a BOSCHE tester (really tight on funds tirght now), but I will check out the ultrasonic cleaner. If I can test the old ones, and they're OK, I can keep 'em as spares.

Thanks for the exploded view on the injector setup. That's a huge help! I've been trying to find the service manual someone mentioned that was available on the MB site, but no luck so far. I'm a complete blond when trying to find things on the internet.

Anyway, thanks for all the help! I'll see about getting all the parts - may be just easier to start with new, if not too expensive, and then start the project.

 

...I've been trying to find the service manual someone mentioned that was available on the MB site, but no luck so far. I'm a complete blond when trying to find things on the internet...

To find the MB Service manual, I googled:

"mercedes w126 service manual torrent"

That should give you a bunch of places to get it. The one I retrieved was about 450MB in size. It took me two tries though. The first one I got was in Russian.

Edit: you'll need a torrent client to download it. I used BitTorrent. Then you just unzip it to a folder and click on the file index.htm to launch it.

 

The pinging could be cheap fuel. I'd change the fuel filter.

 

While it's not totally out of the question, I don't think it's the fuel. I always get 91, but the the pinging happens no matter where I fuel up. I prefer Shell fuel, but have used QT and Giant, with the same results.

I'm thinking it's more maybe inadequate fuel delivery, from dirty injector, fuel filter, or even bad firing if the spark isn't adjusted correctly. I'm getting 20-23 mpg, so it's a mixed blessing

As long as it's not hurting the engine, I can deal with the pinging until I find the answer, especially since I'm tight on funds. It would really suck if the answer also meant 15-18mpg, as documented in the owners manual! LOL

 

I would strongly recommend a can of 44k in your fuel made by bg. It is made specifically for that purpose. The pinging could be excess carbon buildup on the pistons from improper atomization as well. I swear by the stuff. It is amazing. And I have no affiliation.

Every used Benz I ever purchased, I ran a can of that in the tank first before I even tuned it.

 

Even w/ regular the stock ignition map in your car should make 87 workable in all but the Heaviest of loads. As such, BG as RW mentioned above would be a good idea as Heavy build up from lots of lugging about can def. cause pinging.

If your injectors have over 100K and you are suspect, replace them..they do wear out and no amount of cleaning will remedy that.

Check your timing w/ a timing light, should be around 3-5 degrees w/ all associated vacuum etc hooked up @ idle.

Has anyone set your CO/Duty cycle? When was last tune up? What plugs are you running?

Jonathan