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Old 06-18-2008, 02:21 AM
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Join Date: Jan 2007
Location: Olds, AB
Posts: 42
1989 190D 2.5L (W201) - how to replace vacuum shutoff valve?

Greetings, eh?

I've got the air box off, I've got the air plenum off. I even replaced a couple of fuel injector lines that were very old. I'm feeling pretty proud of myself, but now the big work is ahead of me.

How do I remove and replace the vacuum shutoff valve on a 1989 190D 2.5L? My injection pump has the shutoff valve on top, not behind the IP.

I've removed one of the two Torx bolts and clips holding it in place, which works fine. I cannot get to the other bolt, though, because it is right underneath a cylindrical unit with a tiny flathead screw (rusty) and a single nut on top. What does this do, BTW? Is it to adjust fuel mixture?

I wanted to leave the upper air plenum (?) in place - the one that brings the air from the filter into each injector - because I didn't want to remove a bunch of extra things and risk forgetting how to get it back together.

I figure I can remove the cylindrical unit hiding the shutoff valve's second bolt, but I really don't know how I'm going to do that. The nut on top of the cylindrical unit comes loose easy enough, but I can't turn the rusty screw. Should I just WD-40 it and remove it? Should I not touch that thing? Is there any other way to get that shutoff valve out?

Thanks for any help, links to other posts, diagrams, etc.

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1995 E300D, 253000+ km - babied by PO, let's hope I do the same...

1989 190D 2.5, 450000+km - first MB I've owned. Bought at 396000km, and now parked.
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Old 06-19-2008, 12:34 AM
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Join Date: Jan 2007
Location: Olds, AB
Posts: 42
Well, I seem to have fixed the issue myself.

The bolts only come off with a 10mm wrench (and a small one at that). I managed to get the bolt cracked and after about five minutes of turning it 60 degrees each time, the bolt under the cylindrical unit came free.

What I didn't expect is that the new shutoff valve was designed differently than the old one. The old one has clips on either side of it, which the bolts go through. When the bolts are tightened down,, the clips go over the rim of the shutoff valve to hold it in position. The new one has bolt holes as an integral part of the valve unit. So I didn't need the clips.

Unfortunately, the bolt sits very, very close to the side of the valve because of those holes - so close that you can't slide a combo wrench over top of the bolt.

In the end, my Dad and I slid three small washers on to the bolt, so that it would have enough height stay clear of the valve and still sink enough of the bolt into the injection pump.

The only problem I have *now* is that the old unit had its vacuum intake on the side of the valve, whereas the new unit has it on top. Thus, the piece of rubber tubing on the brown/blue vacuum line is too short to connect. I have to go buy some new tubing and cut a piece that will be long enough.

Fortunately, I tested everything by using a bit of clear tubing and some barbs/brake bleeder vacuum tubes I had sitting around. It works perfectly - shuts off when I turn the key off.

Advice:
1) Buy some extra rubber tubing when you change this thing out. You may need it.
2) When you get the valve in place, hold it in position and push the shutoff lever down. You should feel some tension while it goes down, which means you've install the valve properly. This was mentioned in another thread on this forum and it bears repeating.
3) Connect the brake booster hose when you test the shutoff valve by running the engine. My dad and I did a few tests and we couldn't figure out why it wasn't turning off until I realized that the brake booster hose needed to be connected.

Now, can anyone tell me what that cylindrical unit is? Is it my ALDA? The engine is non-turbo, so do I even *have* an ALDA?

__________________
1995 E300D, 253000+ km - babied by PO, let's hope I do the same...

1989 190D 2.5, 450000+km - first MB I've owned. Bought at 396000km, and now parked.
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