Modified my WUR

[billbigrig]

Howdy,

My 81 Audi 5ooo has used about 5 or 6 of them. I still have them lying about. I'll buy a used one, it works for a spell, then stops. Then I get another. What part is wearing out. Spring tension? Mine has one large and one small vacuum line. Non turbo. What is the function of each vacuum line? From the drawing it appears that I need to knock the plug IN to raise system pressure,(lower control pressure.). Is this correct?
Thanx
Rig

[Paulporsche]

I was using an Audi 5000 one on my car for several years. Finally it would not go above whatever the cold control pressure was, even though when the internal bimetal arm was heated it got too hot to hold. I'm thinking it wouldn't bend as designed any more, but it was too hard to tell since it actually bends so little.

It's also possible the filter @ the top for the fuel lines gets clogged.

Sometimes the electrical connection fails.

There are also, as you mentioned, internal springs that can fatigue.

The plug that gets knocked in (down) to lower control pressure and richen mixture could slip upward.

Your engine could require a richer mix as it ages.

If the unit has a thick base, as mine did, then the top line is atmospheric and can be left open or connect to the top port onthe throttle body. The bottom one is vacuum and eventually finds its way back to the lower TB port. As you move from idle to WOT you generate less engine vac which allows for a lower cp and a richer mix. Thin base units operate the reverse.

The system pressure is changed via shims in the fuel distributor.

There are lots of threads on the WUR and testing, and Pelican Jim Williams has a very informative website on the CIS. A fuel pressure gauge is a great tool for helping to diagnose WUR problems.

[Cdnone1]

So do you raise the plug to increase cold pressure?
Steve

[boyt911sc]

Originally Posted by Cdnone1

So do you raise the plug to increase cold pressure?
Steve

Steve,

Yes. Adjusting down the cold control pressure is done by pushing the plug down. While adjusting it up is done by using the nut/bolt set-up to pull the plug up.

Tony

[Cdnone1]

First let me say I love this forum!
I followed advise here and built an adjustable WUR. I used a 6 mm blot and can adjust it while it's on the car. I dialed it no problem


Everything works fine but it is leaking a little gas on one of the lines. I suspect it's from the line from the fuel distributer. My question is should both the line into and out of the WUR have gaskets between the line and WUR.
The input line had what looked like a small brass washer and the output line had nothing
I can not find the gaskets, o ring or washers listed in Pelican and I would really like to get my car back on the road.
Can someone tell me what should be on there. I don't want to fool around when it comes to gas under pressure
Thanks
Steve

[Cdnone1]

So everything is in and buttoned up with no leaks.
My cold pressure is 2.5 bars
My warm pressure after 2 minutes is 3.4
Residual pressure after 20 minutes is 2

The idle hunts up and down over 1000 rpm while warming up. What should I be looking for now?
Thanks

[Gunter]

Adjust the mixture with the engine hot.

Some people use a gas analyzer but I use my ear.

With a long 3 mm Allen key, turn the adjustment screw cw for rich a little until idle gets rough, then turn ccw for lean a little until idle gets rough again. The right setting is in the middle of the 2.
The turns are very small; not more than about 1/4 turn.

Along with the mixture adjustment Allen screw, you also have to use the large slotted idle speed adjustment screw.

Adjusting both screws a few times should do it.

[Steve930]

Just completed this modification on a '83 930/66 and it worked a treat as the warm control pressure was about 3/4 bar below the specified value in the manual (cold pressure was OK). Was able to use the adjuster to ease the pin out (no additional roll pin as it is pretty tight to start with) enough to bring the control pressure back into spec.

[RarlyL8]

Good deal, really makes tuning easy! I showed Mark (Tripster) this mod back in 2008 and we still offer a fully adjustable WUR for 911, 930 and 964T.