83 380 SEL warm-up compensator vacuum connections - PeachParts Mercedes-Benz Forum

bolomiester · #1 08-01-2008, 11:21 AM

My 83 380 SEL has always had a stange start-up fault, which my indy says is a faulty warm-up compensator. (when stone cold it will idle very slowly then stumble and die for about the first minute, then the idle will smooth out, settle down at 650 rpms and run perfectly)

I bought a used replacement but it has different vacuum connections than the one in it now (see photos). Which is right and what goes where?

450slcguy · #2 08-01-2008, 12:03 PM

Quote:

Originally Posted by bolomiester

My 83 380 SEL has always had a stange start-up fault, which my indy says is a faulty warm-up compensator. (when stone cold it will idle very slowly then stumble and die for about the first minute, then the idle will smooth out, settle down at 650 rpms and run perfectly)

I bought a used replacement but it has different vacuum connections than the one in it now (see photos). Which is right and what goes where?

When you buy parts, you need to buy the correct part #. I would think the original one was the correct one if their is only one 1 vacuum hose leading to the WUR.

ctaylor738 · #3 08-01-2008, 12:23 PM

You can try a science experiment by plugging the large outlet on the replacement and routing the line to the small one.

But try this with your existing one. Remove the larger fuel line fitting and use a pick to carefully fish out the mesh filter beneath it. Disassemble the filter into its four layers and clean each one with throttle body cleaner. You need to look closely to be sure all the crud is gone. Reassemble, reinstall, and see if that makes a difference.

bolomiester · #4 08-01-2008, 05:56 PM

I had removed the old one and sprayed a ton of throttle body cleaner in there. Some crud did wash out. Not good enough?

ctaylor738 · #5 08-01-2008, 06:27 PM

No, you need to take the screen out, take it apart and be sure each layer is clean.

bolomiester · #6 08-03-2008, 06:41 PM

Quote:

Originally Posted by ctaylor738

But try this with your existing one. Remove the larger fuel line fitting and use a pick to carefully fish out the mesh filter beneath it. Disassemble the filter into its four layers and clean each one with throttle body cleaner. You need to look closely to be sure all the crud is gone. Reassemble, reinstall, and see if that makes a difference.

How hard can I pick at it without damage? I used a dental pick but it seems like it's in there pretty solid.

ctaylor738 · #7 08-03-2008, 07:48 PM

You need some force. Poke around the edges with a pick. If you put a hole in it getting it out, you can arrange the layers so the hole doesn't go straight through.

bolomiester · #8 08-04-2008, 11:27 AM

Quote:

Originally Posted by ctaylor738

You need some force. Poke around the edges with a pick. If you put a hole in it getting it out, you can arrange the layers so the hole doesn't go straight through.

Yep, that worked. I removed a total of 5 screens. The ones on top and bottom were relatively coarse. The layers above the bottom one and below the top one were finer, and the one sandwiched in the middle was very, very fine. Almost like steel nylon stocking fine.

I soaked them in cleaner for a few minutes, then used a spray can of it to blow through each screen from both sides. When I was done they looked very clean.

I had to wait until this morning to see if it made a difference, as the car needs to be stone cold to exhibit the symptoms. The cleaning did seem to make a difference. Instead of dropping to minimal rpms with repeated stumbling and stalling for a minute or more, it dropped to a couple hundred rpms, didn't stall, then stabilized to a normal idle in about 15 seconds.

ctaylor738 · #9 08-04-2008, 12:52 PM

Nice wrench.

This is as far as you can go without a pressure gauge.

There is an o-ring in the valve that is compressed to increase control pressure (lean) or relaxed to decrease it (rich). What happens is that the o-ring loses its elasticity and can't relax enough to lower to sufficiently lower the control pressure.

You can replace the o-ring but then you need a gauge to adjust the pressure.

That's basically what you get it a rebuilt WUR. A clean screen and a new o-ring, plus a checkout of the electrical, some new screws and nuts and an adjustment.

bolomiester · #10 08-04-2008, 01:43 PM

Quote:

Originally Posted by ctaylor738

Nice wrench.

This is as far as you can go without a pressure gauge.

There is an o-ring in the valve that is compressed to increase control pressure (lean) or relaxed to decrease it (rich). What happens is that the o-ring loses its elasticity and can't relax enough to lower to sufficiently lower the control pressure.

You can replace the o-ring but then you need a gauge to adjust the pressure.

That's basically what you get it a rebuilt WUR. A clean screen and a new o-ring, plus a checkout of the electrical, some new screws and nuts and an adjustment.

Is this something a reasonal diy-er can do? I checked prices on "remanufactured" WURs and they are around $140. I did a little surfing and found CIS fuel pressure testing kits for about that same price, more or less. It's probably worth it to have one in my "kit."

Where is this "O" ring located if I decide to tackle it?

ctaylor738 · #11 08-05-2008, 10:26 AM

The o-ring is in the valve. Here's a picture:

I = o-ring
II = bottom/movable part of valve
III = top/fixed part of valve, with holes in center for in and out of fuel, also has the groove where the o-ring fits

If you want to have a go at it, send me an email, and I'll send you a good piece written by a Porsche 928 guy on rebuilding and adjusting. I also have spare o-rings - the size, which I think is 14-1.5 is kind of hard to find.

bbiggbob · #12 08-09-2008, 11:38 PM

Cleaning my WUR
Hey ctaylor738,

Below is a thread I started...basically, I have an '82 380sel...all of sudden it started to spit and sputter--idles fine...after its warms up a little, no more spitting and sputtering but seems to hesitate with no power.

450sclguy gave me a tip on adjusting the mixture screw through the rubber gorument in the top of the air cleaner and that help a lot, but still lacking power. You can driver it granny style in traffic and on the highway you can go as fast as you want, it just takes a while. No smoke at exhaust but a slight smell of gasoline.

The next tip was cleaning the WUR and thats when I found your thread.

What would you suggest I do?

Thanks for any help,
Bobby

PS Here is the thread i started.... http://www.peachparts.com/shopforu...rm+compensator

ctaylor738 · #13 08-10-2008, 12:39 PM

I couldn't link to your post.

Acceleration problems are usually fuel-related. So if you want to check it out:

0. Buy or borrow: a gauge set with Bosch connections, a Mityvac, an electrical tester with duty cycle setting, and a timing light. You will aslo need a setup to run the return side of the fuel system into a large bottle (2 liters), and figure out how to jumper the fuel pump relay.

1. Jumper the relay and use the gauge set and check system pressure and control pressure

2. While jumpered, do a fuel volume test

3. Still while jumpered, check the sensor plate for smooth movement.

4. Get a Mityvac and check your WUR for vacuum leaks on both sides.

5. Get and check your duty cycle

On the ignition side:

1. Plugs and wires, cap and rotor in good condition?

2. Timing set to spec and vacuum advance working?

You will find posts on how to do all these things.

I'm not sure of your level of comfort with this list, but if you don't want to make the investment in these tools, then you are probably better off finding a good shop. Without the ability to measure the basics, you can waste large amounts of money.

bbiggbob · #14 08-24-2008, 09:05 PM

Hey everyone,

I'm just now getting into my WUR('82 380sel). I found some vacuum issues maybe.

1) Where the vacuum lines split one goes to the front bottom WUR and the other goes to an inlet split into the top of the intake manifold, I found a cracked hard line that was leaking and fixed that.
2) Checked the vacuum on the big one on the bottom facing towards the back, ok.
3) Where does the one on top of the WUR connect to? Mine has a little rubber elbow vacuum line fitted and it doesn't connect to anything. I look all over for a connection nothing. Is it just a vent? I put my MityVAc on it and it wont hold a vacuum very long it leaks off real slow.

Thanks for any help,
Bobby

ctaylor738 · #15 08-25-2008, 10:03 AM

The fitting on top is a vent.