Re. Warm-up regulator questions

[Louis-Alain Richard]

Ben and all,

I followed the advices, and ran the fuel pressure tests today. Surprise,
Geraint showed its nose this morning, maybe posting to thousands of listers
has something to do with this ? :-)

Obviously, as many of you said, the WUR on the car is perfect, every
pressure are within specified range. 
- 6 bar system pressure
- 1.5 bar cold control pressure
- 3.6 bar warm control pressure
- 2.4 bar residual pressure after 10 minutes

I also opened the other WUR to check its innards, and they were quite nice,
not much crud in there. 

I also took the opportunity to check the 2 thermo-pneumatic valves (055 131
851C) I have in my parts stock. This is the small black plastic sensor with
2 vacuum nipples that is installed below cyl #5 and controls the
vacuum/boost going to the WUR. (Don't confuse it with the big brown
thermo-time switch that is installed at the back of the head that controls
the cold-start injector). Here Steve and Ben, you are wrong: this
thermo-pneumatic valve is normally open when cold, then shuts when the
engine is hot (around 100C). Now I'll replace the one on the engine now as I
don't know its condition. I doubt it will change anything for my warm-up
problem, though.

But the fact that no vacuum or boost reach the WUR when hot means that this
special and very expensive WUR is only different from a garden variety WUR
for the warm-up phase. And it means that the 2 different diameter ports on
it are there for what Steve B said, like an accelerator pump on a
carburetor. If boost rise suddenly, then one chamber will receive more
pressure before the other one, richening the mixture for a few seconds. 


That leaves me with an air problem, instead of a fuel problem... The
auxiliary air valve is still suspect. I will take a look at a new one to see
if the 3 I have here are dead, or they just need a bit of cleaning and
adjusting. More to come.

Louis-Alain



-----Message d'origine-----
De : Ben Swann [mailto:benswann at verizon.net] 

The WUR is often one of those things that may or may not need attention and
you won't know until you open it up.  Running fuel pressure tests before
doing that may give a clue as to if it is operation correctly.

I have a few I rebuilt and they did operate in range after that, although
problems I had ended up being related to something else although I did find
some debris in both.  Usually there would be a tiny bit of crud that can be
carefully cleaned out.  I've had a few that required a little 1000 grit
paper to polish off a little rust area on the diaphragm. Disassemble and
reassemble with methodical care.

There are two ports on the UrQ WUR and they can likely be used differently
than the stock application to provide additional enrichment on boost, but I
found that to be unnecessary. I did think it strange how since the two port
counteracted each other that both wer tee'd into the same manifold pressure
port.  What I found in testing is one port I think the one that enleans is
about 3X the force of the one that enrichens, but forget and it may be the
other way around.  So, basically works per design OK when all is operating
normally.  The thermo-time switch/valve opens when warming up - AFAIRC and
puts the warmup circuit operating to enlean.

I'd have to check my notes I scribbled on the factory training printout I
made to see if what I said is backwards, but basically you can take them
apart carefully and see how they work when cleaning - just be methodical. 
If you find rust, things may be beyond a basic cleaning, but may still be
worthwhile to try.