1990 W124 300D Problem
 

Hi.
I'm new to this website forum and hope i can get some friendly advice.

I have a W124 300 six cylinder diesel estate (UK term for stationwagon?).
Anyway, since filling with biodiesel several compression leaks have started from near to the injector bodies.The leaks (sounds like a chuffing noise) are from the same place.
There appear to be small holes in the head just next to the steel inserts that take the plastic heat shrouds, and the leaks appear to be coming from there.
The engine is running badly with plenty of smoke from the exhaust.
I also noticed that the coolant temp went higher than normal and i get a lot of clatter on tick over.
My thoughts on this are that the biodiesel is causing pre-ignition. The mixture is igniting in the pre-chamber for some reason.

Any help greatly appreciated.

Ian
England, UK

Given the cost and effort of replacing the heat shields, that's where I'd begin even if you don't agree with the logic.

Is this a SOHC or DOHC engine?

Sixto
93 300SD

The engine is a 603.912 .
There is definately compression being lost .I cannot see that just by replacing a plasting heat shield, the problem will be solved.

The heat shields are made from a hard plastic which locate in this steel ring type insert in the head. The injector then slips between to screw it into the head.
The shield obviously is not a tight fit around the injector and could be classed as being cosmetic as i have seen on some engines these shrouds or sheilds are broken for the most part.

Maybe it is the injector sealing washers, and the compression is finding it's way up the back of this metal insert somehow.

The engine ran fine even from stone cold until i filled with 100% Biodiesel. Within 10 miles smoke was coming from the exhaust and this chuffing noise coming from this hole near to the injectors.

I hesitate to transfer this thread myself as you have some answers already, but I heartily encourage you to start another thread on the Diesel forum too.
http://www.peachparts.com/shopforum/diesel-discussion/

Gilly

Could be a terminology issue. I don't mean the plastic shrouds around the injectors. I don't think those are heat shields but I don't know what they are. When they break in the US, the dealer doesn't replace them. I mean the heat shields between the prechamber and the firing tip of the injector.

These things -

http://catalog.eautopartscatalog.com/mercedesshop/sophio/wizard.jsp?partner=mercedesshop&clientid=catalog.mercedesshop&baseurl=http://catalog.peachparts.com/&cookieid=1UF05A51E1XC0VPIWH&year=1993&make=MB&model=300-SD-003&category=All&part=Injector+Heat+Shield

Sixto
93 300SD

Sixto, those parts you linked to are the injector seals, those need to be there. The place I was at always replaced the plastic part too, but can't remember what they called them in the shop.
Gilly

The guys at Smythe European said NLA.

Sixto
93 300SD

I think they called the plastic parts "shields". I assume you mean THOSE are NLA. The injector seals still HAVE to be available. They just do............
Gilly

Yes :)

The guys at Smythe told me the plastic shroud things are NLA. Maybe they're called shields. I don't remember.

The heat shields are definitely available. For some reason dealer ones are black anodized and third-party ones are shiny brass colored.

Sixto
93 300SD

The part you posted a picture of are called injector seals, never heard anyone refer to those as heat shields. Oh well, as long as you can get 'em I wouldn't care what they call 'em.
Gilly

I've always called them that. Then again I call my kids by each other's names :)

Sixto
93 300SD

Gilly, could the biodiesel have caused the prechamber seals to leak?

I've never heard of this personally, but I suppose it's possible. If that were the case, compression would leak out around the prechamber lock ring.

I've seen a leaky injector seal (had two in my old 220D as the old original "tophat" seal was still in there and I put a new ring type seal one top). Won't cause serious compression loss though, just ooze.

The other possibility is that there was considerable suspended glycol/sodium hydroxide sludge in the biodiesel, but that would have affected every vehicle filled up with it. Would wreck the IP first, I think.

Peter

Peter
I think there's guys at the Diesel Discussion forum that would know better than I. No clear idea on my part on why the fuel type would bother the injector seals.
Gilly

OK. I think i have found my problem here;

http://www.peachparts.com/shopforum/diesel-discussion/120712-help-injector-prechamber-heatshield-leak.html


But why would this start straight from using Biodiesel?

Ian

Sounds like the original poster expected to find compression seals like in the 61x engines.

My guess is the compression leak is unrelated to using biodiesel. Just a coincidence.

I use a magnet to remove the injector seals. Once I did a compression test without removing the seals and they all jumped out. If they're stuck, try cranking the engine with the injectors off.

And I'm not the only one who calls them heat shields :)

Sixto
93 300SD

When i use the term 'shield', i mean the black plastic/bakelite shroud around the injector not the sealing washer type thing.
New metal seals were fitted but this did not cure the problem.

I could agree on coincidence if just one cylinder was affected but not all at the same time.

What appears to be happening is the injected fuel is burning quickly in the pre chamber before it should (pre ignition).
I noticed there was a slight rise in coolant temperature too, following the fill up with Biodiesel.

I have replaced the pre filter and main filter but there was nothing contained in them to warrant a problem with the fuel supply.

Sounds like leakage around a prechamber. It will make that chuffing sound.

I guess there's two paths to lose compression - one on the outside of the prechamber the between the head and the lockring; the other on the inside of the prechamber through the injector seal and between the prechamber and injector. I'm not sure how tightly the prechamber taper sits against the boss in the head but I imagine the lockring imposes quite a force creating a seal. How that seal can come undone with just a tankful of the worst fuel ever is puzzling. Similarly I don't know how an injector seal can deteriorate over the course of one tankful.

Can you use drops of fuel between the injector and lockring then separately between the lockring and head to isolate the leak?

Sixto
93 300SD

The leak is definately from the outside of the lock ring.
My injectors are the slanted orientation type.

When i said i had just filled up with Biodiesel, i meant just less than 10 miles earlier before the problems started.

I believe the leaks have been caused as a direct result of using the Biodiesel, there is no other explanation.
Somehow the fuel isn't being burnt properly as it is igniting too early in the prechamber or the fuel has caused a problem with either the injectors or the pump.

I have changed both the pre filter and the main filter. Both did not show any signs of blockage or foreign particles.

All the glow plugs are glowing fine as well as the run on period until they are timed out.

This is a link to the area of concern, the prechamber; http://www.peachparts.com/shopforum/showthread.php?t=120712

I need to find the cause of the pre ignition to prevent the excess compression in the pre chambers occurring in the first place.

Next thing to pop into my idle mind is that there was too much gasoline/petrol cutting the biodiesel blend or the pump was mislabeled.

Take some of what's in your filter to be analyzed. Or just smell it.

Sixto
93 300SD

I filled two jerry cans at the same time so i could get that sampled i suppose.
When i got the car home i syphoned off half of the fuel tank and went and filled with normal petro diesel.
Do you think the two will have mixed properly?
I also found that one of the hoses from the pre filter to pump was slightly loose.

Just and update on events.

I have had the injectors tested and they are fine. The pump timing is correct too.

I flushed out he biodiesel,fitted another filter and restarted.
The engine runs significantly better. Only two of the six prechambers are leaking now. Smoke is still evident and smells like and old bus starting from cold.

So it is obvious to me the biodiesel was the problem, the detonation/preignition has damaged the prechamber seals.

The supplier of the fuel has still not replied to my emails or phoned me.:mad:

What should i do. Obviously i now need to rectify the two leaky prechambers but surely the fuel supplier has some liability here.

















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