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Old 12-05-2011, 07:32 PM
thebenstenator's Avatar
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W124 Fuel/Smoke Issues

Ok, So short story of what's recently happened to my car. (Just before I start I'll just mention that I did all R&R stuff at home, no shops). Recently I discovered that the head was cracked. I had taken it off and to a machine shop and it was indeed cracked. So I looked around for one and eventually found one at a junkyard, bought it, took it back to the same machine shop, they did a full valve job, planed it, made it look all nice and a pressure test just to make sure it was ok, and it was/is.
When I got it back they gave it to me with some parts out of it that I didn't know were removable (where the injectors actually screw in. They gave me the special tool that they had to use to remove them). So I put it all back together at home, put the head back on and got everything in order. It started great, first time. I was very pleased.
In the owners manual it says that the coolant system holds 10 liters or quarts or something. I had emptied out everything, even the radiator, on this head job so I figured I'd be putting exactly 10 quarts in there. Alas 10 quarts did not fit. I filled up the radiator by using the hose that goes from the top of the radiator to the head, then I started pouring the fluid in through the overflow container, until it was full. I figured that once the engine got hot and the thermostat opened up it would suck more fluid through and I could put the rest in. That didn't happen. Then I thought that there might be air bubbles in the system and that if I ran the car with the overflow cap off it might purge out the air bubbles.
While I was doing this, I noticed a lot of white smoke was coming out of the tail pipe and that on the 5th (I believe, either the 5th or the 1st, feel free to clarify) injector it was leaking fuel and bubbling.
Please see video for clarification.

Fuel-Smoke Issue - YouTube

phew, so much for being a short story.

But Anyway, I believe that much of the fuel leakage is coming from the black fuel lines that connect each of the injectors. The injector is wet all the way up. The metal fuel line is tight as I can get it.

My biggest question is about the white smoke and the bubbling coming up from underneath the injector.

It was THOSE pieces (underneath the injectors, that they actually screw into) that I had to install myself, could it be that maybe that one's not tight enough? Or could the injector not be tight enough? Or is there some other problem that could cause this?

The crush washers are installed, I'm pretty positive that I tightened ALL pieces (injectors, injector cup thingies [if anyone knows the actual name of those things... feel free to let me know]) to torque specs. I just didn't have the torque specs on those one pieces. . . (need name), but I got them ALL as tight as I could get them with a breaker bar, soooo, they should all be the same and the other ones don't have a problem.

Anyway, this is getting really long. Just trying to answer some questions before they're asked. Any input is appreciated, thanks and may all have a very Benzin Christmas, or any other holiday that you celebrate.

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Old 12-05-2011, 07:55 PM
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they are called prechambers.. it looks like either the prechamber or injector or both are loose.
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Old 12-12-2011, 08:53 PM
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ok, so I've taken off the injector and tightened the prechamber as much as I can. That with a big breaker bar. I was able to turn it about 1/8 of a turn or so. So that's good I guess. I put in a new crush washer and tightened down the injector and. . . it seems to have slowed the leak, but not fixed it.

Is it normal for air to escape from the prechamber (thanks for the name btw)? I still believe that the main fuel leak is coming from the actual rubber fuel lines, I'm just worried about the air escaping, if that's a problem.
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Old 12-12-2011, 08:56 PM
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I would replace the injector return lines with the braided stuff every time they are removed.
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Old 12-12-2011, 10:55 PM
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Quote:
Originally Posted by thebenstenator View Post
ok, so I've taken off the injector and tightened the prechamber as much as I can. That with a big breaker bar. I was able to turn it about 1/8 of a turn or so. So that's good I guess. I put in a new crush washer and tightened down the injector and. . . it seems to have slowed the leak, but not fixed it.

Is it normal for air to escape from the prechamber (thanks for the name btw)? I still believe that the main fuel leak is coming from the actual rubber fuel lines, I'm just worried about the air escaping, if that's a problem.
Couple of problems. The protrusion of the Precombustion Chambers where they stick out of the Cylinder Head was supposed to be measures so they do not stick out too far. You did not say that you checked that.

When you remove metal from the Cylinder Head the Prechambers stick out more than they did when the Head was unaltered.

The next thing is that both the Prechamber Retaining Rings/Collars and the Injectors have specific Torque values they need to be tightened to.
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Old 12-12-2011, 11:16 PM
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You said:

I still believe that the main fuel leak is coming from the actual rubber fuel lines, I'm just worried about the air escaping, if that's a problem."

First thing . . . replace the fuel return lines ASAP. They leak with age, and there's a new formulated return line material to deal with the new diesel formula. You'll also need to burp the return lines to get the air out.

Also, the body of the injector can be leaking . . . put on vice grip and tighten and put back.

Read about the problem with some of the fuel that people are getting that's bad. Hunter posted it as a sticky in this forum.
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Old 12-13-2011, 07:29 AM
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For the return lines I use 4mm polyurethane hose, which is typically used for compressed air. It is very cheap and you may find it in any hydraulics shop. I fitted it more than a year ago and it is holding up great. It doesn´t crack and it doesn´t go stiff over time.

As for the air leak, it seems that everybody who remove the pre-chambers end up with a leak upon reassembly.
I guess you should pull the chamber out again (remember to remove the GP first), make sure all the mating surfaces are totally clean and put it back together.

Good luck
gonzalo

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