# WUR troubleshooting - control pressure too high



## autoarcheologist (Jun 14, 2017)

First I want to thank everybody who contributed to the CIS knowledge over the years. I have been reading many of the threads here, and using www.cabby-info.com to help diagnose a 1985 Cabriolet we recently picked up. I also have a copy of the Bentley that thankfully came with the car.

When I bought the Cabby it would barely start, or rather took 5-10 attempts to start it. But it would eventually run poorly until it warmed up a bit. Once warm it runs great, has lots of pep, and is a ton of fun.

I first checked the in tank fuel pump and found it wasn't working. So I replaced that, and also sucked out as much rust and sediment as I could out of the tank. I had to zip-tie the screen to keep it on upon reassembly but it seems to be working great now, and easily passes the flow test.

But it still starts hard and requires multiple attempts. It will start and run for 2-4 seconds then die. I assume as the cold start injector bleeds off it's running too lean and dying. I disconnected the cold start injector and it won't start at all.

So I picked up a CIS fuel gauge set and I have been attempting to test the pressures, and here's where I'm stuck.

I have great system pressure, I measure 72 PSI at the top of the fuel distributor.

But when I measured the cold control pressure the first time it was exactly the same.

I remove and cleaned out the WUR, and found the screens to be totally blocked. I cleaned them out, and at the moment I'm just running without them. I can blow air easily through the WUR with the fuel hoses disconnected, but it doesn't taste good.

The control pressure dropped slightly, but was still over 60 PSI.

So I replaced the o-ring inside the WUR. This helped a bit more, now I'm down in the 50s. But the Bentley says it should be closer to 20 PSI, and it still starts then stalls immediately.

I have tried measuring the cold control pressure with the WUR disassembled, so there is no pressure on the P-spot or center of the diaphragm. According to this site - http://www.benzworld.org/forums/w126-s-se-sec-sel-sd/1372083-warm-up-regulator-wur-calibration.html - the control pressure should be only 0.5 bar or about 7 PSI with no pressure on the diaphragm. But I'm still getting almost 60 PSI.

I also just tried removing the main pressure regulator from the side of the fuel distributor. The o-rings are still soft and I didn't see any dirt or anything that suggests it's not working right.

Any ideas on what else could be causing the control pressure to stay high? I'm planning on trying to crack various hoses to see if pressure drops, but that's a messy procedure and my garage is already covered in gasoline!

I should also mention that I have checked the injectors and O-rings and they have good patterns, and the o-rings are still pliable. I have new ones I plan to install anyway, but it runs fine once running. Good idle, excellent acceleration. It's just the cold running pressures that have me stumped.

I also pulled the return hose to the tank and I can blow into it and hear air bubbles in the tank. Again this doesn't taste great... but in the name of science!

What should I try next? Clean out the fuel distributor? Maybe the center plunger is stuck?

Bad main pressure regulator?

I'm trying to approach this as methodically as possible, but I'm new to CIS and a bit stumped.

Thanks!
Ian 
Portland, OR
1985 VW Cabriolet Wolfsburg

PS - I have played with mechanical fuel injection for years on Alfa Romeos, but it's a COMPLETELY different approach and system. It has been fun to learn a different way to skin this cat.


----------



## WethVento2.0 (Dec 29, 2016)

not sure what to suggest but one thing jumped out at me.

Pretty elementary but still ... 

Is your fuel pressure gage hooked up between the middle line on the fuel dizzy and the line that goes to WUR?? 

if not, then it should be. 

I hope this helps.


----------



## [email protected] (Aug 9, 2016)

I had a very similar issue with my '84 Gti. Just like you, I couldn't seem to get my control pressure down to 20 psi even after removing and cleaning the WUR twice. Finally after removing and disassembling the WUR for the third time, I had success. I ended up separating the two halves of the WUR and putting the top half into a bench vice to hold it in place. Then I tapped the threaded end of the adjustment pin with a hammer until the pin was protruding about an 1/8th of an inch above the surface of the WUR body (see step 4 of this: http://forums.vwvortex.com/showthread.php?4587975-Warm-up-regulator-(WUR)-Calibration

I had to hit the pin really hard repeatedly to get it to move. I then reassembled the WUR and reattached the two fuel lines. My cold control pressure dropped to below 5 psi and the engine started and ran. I tapped the pin deeper into the WUR to adjust the pressure to 25 psi and the engine runs pretty good now. In my case it was all about the position of the PIN in the WUR. Good luck!


----------

