The fuel line in the photo is the line from the fuel thermostat in the cyl head to the pre-filter.

Mine drains back when motor is off.

If you have wetness anywhere, resolve it first.

Mine does the same thing. No issues. Disappears when the engine's running. Reappears at shutdown.

I can't tell by the pictures if you do have a problem with the connections inside of the relay module, but since you're not new to this soldering thing, you may be correct that you do not.

I could see extremely fine cracks in a number of the joints on mine, before I resoldered it. They would have been easy to miss.

As for the air bubble ahead of the pre-filter, I have that too. Looks about the same as yours when it's shut down.

Bump.....

Hey, Carleton, what's the status? Or have you just :behead: your W210?

Think I found THE leak.
 

O.K. So I calmed down and taped my compressor hose to the diesel fill pipe,set my regulator for 5psi,removed the intake manifold and saw drops of fuel coming from the bottom of this shut off valve?

Not taking anything for granted,looked underneath with a mirror and saw the fuel was NOT coming from the lines but the body of the valve where it meets the block,took it off and guess what? the O ring has no seal,no friction,totally loose,while I had drops there was also streams of fuel running down the side of the block,gonna get a new O ring or 2 and see if this cures the stumbling and nailing along with the crappy mileage I've been getting.

Thanks to all of you guys for bearing with this sh-t,****** plastic & rubber...

http://i5.photobucket.com/albums/y18...te/shutoff.jpg

Mines doing the same thing and I think I am going to try a Viton O-ring from McMaster ala ncof300d's idea. Can you please measure and post the ID of the port on the IP and the OD of the valve if its not too much trouble? I'm traveling at the moment and do not have access to do it myself.

It's always a good idea to get under this kind of car and inspect closely for fuel leaks. The fuel system on this car has got to be one of the worst designs when it comes to durability.

Hole in the block is approx,16mm,the o.d. of the valve,13mm.

Hey,
Here are the o-rings sizes....

Snap-on Hose seals
O-ring
13mm OD
8mm ID
2.5mm thick

Shut-off Valve seal
O-ring
17mm OD
12mm ID
2.5mm thick

Your shut-off o-ring is the one that I had go bad about a year ago. The odd thing is that it did not cause it to run abnormal at any point....it was just hard to start after setting. You can purchase the o-rings from McMaster-Carr in Viton. Pricey, but they will last much, much longer. If you order today before 3pm you could have them by Mondady-Tuesday.
I am so glad that you found the problem. Wish I was with you to help share the frustration.....I know what it is like with these W210's

Thanks loads for the advice and encouragement....I was losing alot of fuel,probably alot of air got in there when the fuel leaked out overnight?

I slapped it back together with new O ring on the shutoff,nice and tight this time. I also replaced all the plastic fuel lines,filters,et,al.

Started it up and let it run the air out of the system,after a few minutes the smoke and stumble cleared.
Now I'll let it sit overnight and start it cold tomorrow morning THEN we'll see if she acts up again,keep you all posted.

What ever happened to metal banjo fittings with copper crush washers,too expensive?

Update.
 

Let it sit overnight for 16hrs. Started it this morning and let it idle for a minute before driving on 25A,so far no smoke nor loss of power at the usual interval AND when I punch the accelerator there is no longer a flat spot followed by mild surging,the response is pretty instantaneous and smooth,so perhaps it was a number of fuel issues and now that everything is new and tight perhaps I have repaired it.Time will tell.

Gonna run it on the parkway soon and wring it out,then let it sit overnight again.

Going to Connecticut on Saturday and I'd like to drive it up there so I'll keep my fingers crossed.

Good to hear that it is running OK.

Thus far so good.

Going on vacation to Conn,for 4 days so wish me luck,burn incense,slaughter a fatted calf,whatever.

If the car makes it without misbehaving in the mornings not only will my waning faith be restored in the car but in my own feeble abilities as well since nothing succeeds like success.........

Thanks for all the information here. I keep putting links like this in one folder for the day I replace all the fuel lines, O-Rings etc. When I do it I want to make certain I just go ahead and replace everything all at once and do the Viton. Hopefully, I'll do it all in a couple of months.

Well, the only advice I can offer is don't let it intimidate you.
One observation:it seems mileage has no bearing on the O ring deterioration since of 5 people on this forum who have '98-'99 606's the mileages vary widely from 45000-175000,I think it's just age affecting lousy materiel.

One cardinal rule I sometimes forget is that most problems are very simple in origin and repair,sometimes{OK,MOST TIMES} I get overly technical and look for complex causes but 95% of them are ridiculously easy.
Took it out again this morning,drove it @ 45mph for 4 miles,no problem,no stumble,looks like the O rings did it so off to Connecticut we go,keep yer fingers crossed.