PeachParts Mercedes-Benz Forum - 300SD vs 300TD Fuel injector discrepencies

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300SD vs 300TD Fuel injector discrepencies

I have both a 1984 300SD and a 1985 300TD. Engines being identical, the fuel injectors look completely the same, except when I took them apart to replace the injector tips (with bozios), I found out that the one on my 300TD has longer internal springs (compensated by shorter discs that go between the spring and the injector tip). Also, the T-shaped piece that goes between the spring and the disc is shaped slightly differently (shorter) also.

Now otherwise they look identical, so I'm wondering if the differences (ie the different spring lengths) makes a difference somehow? Just observing generally how they fit, it seems like there would be more fuel able to enter into the injectors (from my 300SD) which have shorter springs and longer T-shaped pieces - there seems to be a larger gap making more fuel accessible to the disc and injector tip.

I had put the new nozzles on a few months ago, but didn't have a torque wrench, so I suspect some were on a bit loose. Though apparently I wasn't too far off with using a rubber mallet to tighten them. Either way, I noticed the final (closest to the firewall) injector tip was all greasy and black (ie motor oil????).

Why would it do something like that? Was it perhaps not firing in that cylinder?

Just using a torque wrench with the bozio tips and re-cleaning the threading of the injector halves (it had a lot of greasy grime/grit), I finally get that performance on my 300TD comparable to my 300SD. It feels much more spiffy compared to just a few hours ago, when it felt like something was being towed.

Quote:

Originally Posted by tomas_maly (Post 2840233)

See the pic post #2;there is 2 types of Injector Bodies and Nuts. The interior parts are not the same and in theory the parts are not supposed to be mixed.
I know from experience that if you mix some of the parts when you torque the Injector Nut down it can crack off the End of the Injector Pintel/Needle.
As as a check to prevent this from happening turn the Injector Nut down as far as you can by Hand and take a look. If the Nut is not screwed in enough you may have some of the wrong parts inside.

http://www.peachparts.com/shopforum/diesel-discussion/308510-1986-190d-injectors.html

I used VW Rabbit Diesel Injector Bodies for the first set of Injectors I rebuilt for my Mercedes. I do not know if there is differences in the Springs and so on or not.
When you rebuild or take apart Injectors it is a good idea to keep all of the parts for one individual Injector segregated from the rest.
This slows up the cleaning a little but helps out some when it comes time to set the opening/pop pressure. And, helps to idiot proof the job.

The injectors from both vehicles resemble the ones on the left. They are identical on the outside. Only the internal parts differ. I'm just wondering what the difference is, since it's the same engine model. I.e. why were two varieties made?

Quote:

Originally Posted by tomas_maly (Post 2840531)

Someone mixed the parts but found a safe combinaton that did not damage anything.
Also Monark makes complete Injectors. I do not know if the inside parts are the same as the Bosch ones.

Now that I think about it, the writing on the injector was a bit different. One said BOSCH, the other didn't just said GERMANY. It might be BOSCH too, I dunno. I guess either way the pieces need to be kept intact. I just imagined that for there to be a difference in internal parts like that, there must have been some practical reason that affects the fuel injection...

Quote:

Originally Posted by tomas_maly (Post 2840669)

I do not remember if it was a VW or Volvo Forum but the thread was about different spring strengths and lengths inside of the Injectors.

But in the end as long as the Spring has enouh clearence to allow the Pintel Needle to lift and the Pop Pressure is set the only effect that a stronger Spring would have is to return the Pintel faster. And, that would happen after the Fuel is Injected.

Also that plate that goes between the Nozzle and the Upper Injector Body limits the upwards travel of the Pintel when the Fuel is injected.

Another thing is that Mercedes uses the same Injector Bodies on other makes of Engines.

I believe the Bosch Injectors always have Bosch on the upper Bodies or their Logo.
The Monark Injectors have a Crown stamped on them.

Quote:

Originally Posted by tomas_maly (Post 2840669)

Now that I think about it, the writing on the injector was a bit different.

Like a different part number, perhaps?

I have encountered the situation that you describe. But the part numbers were different.

Unfortunately, I don't have any insight regarding the advantage(s) of one spring length over the other.