View Single Post
billjam billjam is offline
Certified User
billjam's Avatar
Join Date: Aug 2007
Location: Perth, Western Australia
Posts: 2,003
WUR problem - allows air in/out with no restriction

I have an event looming that I need the car in good shape for so I thought I'd do my annual check of fuel pressures and pump and injector flows because I had noticed a few small changes in the way it was running.
A part of the fuel system check is to pressurise the WUR to 0.5 bar to check that it drops pressure fuel pressure under boost.
This is a modified WUR from Brian Leask that has worked flawlessly for the last couple of years.

When I applied air to the WUR (yes, definitely less than 0.5 bar!), all I could hear was air leaking out from somewhere around the WUR. I was able to blow and suck easily through the WUR boost connection, so I pulled the WUR to find the leak. The air leaks out from the hole through the warm pressure adjusting screw in the bottom. As it says in the pic, air pressure (or vacuum) in the main chamber can only escape down through hole B if cone A isn't closing it off. EDIT - I just rechecked this and there is no way that these two parts can get close enough together for A to block hole B, so should there be something else in this hole?

There was no restriction to blowing or sucking air regardless of whether the WUR was hot or cold, so clearly, the cone A isn't closing off the hole. So what is supposed to stop air from passing throught this bottom hole (used for adjusting warm pressure)?
This could explain why my off-boost AFRs have been a bit higher than usual lately as unmetered air has been entering the engine via the WUR.

I guess my question is - what's the problem here?
What could have changed to have caused this problem? Has a sealing plug dropped out of the bottom hole? Can't find anything lying around.

Everything looks OK in the WUR. The diaphragm is good and the WUR increases fuel pressure within specs as it warms up.

1988 Carrera - 3.6 engine (with ITBs, COPs, MS3X) and a whole set of turbo body panels waiting in the attic.
Day job ...
Memories: '68 912, '72 911T, '80 911SC, '84 911, '85 930, '86 930, '87 911

Last edited by billjam; 11-05-2010 at 09:39 PM..
Old 11-05-2010, 08:42 PM
  Pelican Parts Catalog | Tech Articles | Promos & Specials    Reply With Quote #1 (permalink)