300SDL Injector Heat Shields Required?
 

I've got a leak where the hardline goes into the top of the injector. Fuel is bubbling out around the hardline on top of the the nut that holds the hardline on the top of the injector. I've pressure tested the line and it does not seem to leak or have any crack in it. My next step was to remove the injector to see what parts I need to order to replace the injector. From my research here it appears that I need the injector and a replacement heat shield. However, upon removing the injector, I've found that there are no heat shields on any of my injectors. The injectors are screwed into the pre-chamber directly. I can see the slotted pre-chamber ring. Sooo, do I need heat shields are not? While we are on the subject, would a failed injector force fuel back and around the taper on the hardline so that it bubbles out where described above?

I would continue to suspect a bad fuel line. Maybe the ball end of the line wasn't seated properly in the injector cup.

You should replace the injector seal, the nickel size ring that goes between the firing tip of the injector and the prechamber. Drop a magnet or a pick into the injector hole to see if you can dislodge a camouflaged seal. If not, give the engine a quick crank with the stop lever down to see if the old seal blows out.

Kinda hard to describe how to check visually if there's a seal in place. The seal has a smaller hole than the prechamber but the difference is like 5mm for the seal and 7mm for the prechamber.

Sixto
93 300SD

on my 79 TD na 617, the seals were at the bottom of the injector seat. one of them was so carboned up, that it would not come out without major cleaning, and scraping... the bottom of my injector seats was convex, and the shields/seals, were flat with a small 1/4" approx hole drilled in it. the PC hole looks cast as opposed to drilled.
John

So can I get the seal from Fastlane? What about heat shields. I thought these went at the top of the prechamber on top of the slotted ring and would be visible without taking the injector out. Do they actually drop into the prechamber?

Injector seals are commonly available.

I only know of plastic shields for splined lockrings. I've never seen one for a slotted lockring. Shields for splined lockrings are no longer available. EPC says it's okay to go without. You'll have to ask Phil (Buy Parts link at the top of the page) if anything's available for your car.

The shields I'm familiar with engage the splines in the lockring. In fact the splines clock them. They slip onto the lockring then the injectors go on.

Sixto
93 300SD

http://www.dieselgiant.com/mercedesinjectornozzlereplace.htm
this will show you what the heat shields look like, and where they go. basically, they go in the PC before you screw in the injectors...skip all the injector take apart stuff, and look at the reassembly pictures at the end.
John

It been called to my attention that there are injector seals that go between the injector firing tip and the prechamber and plastic shields that shroud the exterior of 1990-up (possibly some earlier) injector bodies. The function of the plastic shield eludes me. Some call it a heat shield but how does plastic shield heat? And what heat is it shielding? A lot of us call the nickel size inector seal a heat shield but by the same token it seems more of a seal than a heat barrier. If anything its presence serves to conduct heat from the prechamber to the injector.

Shoot the messenger if you want but it won't change the nature of the underlying debate :)

Sixto
93 300SD

The pics from DieselGiant help. I can see now where the heat shield/seals are installed.

Sixto- the leak just appeared one day. Started smelling diesel and opened the hood to find diesel pouring down the side of the engine. I've taken the hardline loose a couple of times and re-installed but it still leaks. Any suggestions on how to get it to seat properly? If the hardline is bad, where can I get a replacement?

CB,

just to throw in my experience. I had precisely the same symptoms recently and ended up replacing the injector nozzles and that did the trick. I believe that if your injector is hopelessly clogged it can provide enough back pressure to leak at the injector line fitting no matter how well it is seated.

good luck.

prc

prc - my diagnosis exactly. I may take the plunge and order a set of Bosio nozzels and seals from DieselGiant and do them all at once. I have about 170K on the clock and as far as I know I've got original injectors. I bought the car at about 100K and I've never replaced them.

I should have mentioned that even though I only had one leaking line, I replaced all nozzles with bosio (from Diesel Giant) and the improvement in cold starts has been dramatic. Highly recommend.

good luck

How long have you used them?
 

DG says he will post further driving stats at a later date, but it's been about 6 months since he put that pictorial on, and no updates yet...
just wondering how mileage is affected, how overall power seems to be affected, and such things.
John

they've only been in for about a month, but they are handling the cold snap up here quite well. No data on mileage yet and I adjusted the ALDA at the same time so performace improvement is difficult to assess. Sorry to say that I can only report a dramatic improvement on cold starts - and this is in the context of GPs that are less than one year old.

p

update
 

I swapped a couple of injectors around and the leak stayed with the hardline (did not go with the injector), so apparently it is not the injector. I completely removed the hardline from the car and put it under vacuum. It does very slowly leak down, so I appear to have a very small pin hole down close to the nipple. I wrapped the end with electrical tape and the vacuum did not leak down. Anyone have a source for the hardline or know of a way to repair it?

Get one from a wrecking yard. Only #6 is unique to the 603. #1-4 are shared with the 601 (190D 2.2), #5 is shared with the 602 (190D 2.5, 300D 2.5). I have a spare #4 if that's what you need.

They list for about $30 each from a dealer.

Sixto
93 300SD