here is a great start for a mixture baseline using the push/pull method.
http://forums.pelicanparts.com/porsche-911-technical-forum/232089-cis-idle-speed-mixture-setting-without-analyzer.html?highlight=cis
What exactly is the cold start problem?

CIS Fuel Gauge Tester....
 

JLG,

A CIS fuel Gauge kit is a good investment and probably a tool to have for SC car owners who like to troubleshoot CIS performance. Without knowing the system and control fuel pressures (cold), trouble shooting a warm up problem is a shot in the dark.
http://forums.pelicanparts.com/uploa...1152241512.jpg
These Bosch WURs came from the junk yard (VW, Saab, MB, Porsche, etc.) and knowing their cold/warm delivery pressures becomes very important for its application. These are my assorted WURs and they all work for my '78SC. Good luck.

TD

Mysterytrain,
The car surges and backfires back through the popoff valve in the airbox when cold. It smooths out quite nicely when warm.

Sounds like the typical symptoms of a cold control pressure that is too high, resulting in a too lean condition when cold. You should search this as there are graphs of control pressures and setup and testing procedures for using the gauge. Check WUR and Knocking the Plug.

I just purchased all the parts to make an adjustable WUR. I just have to wait until the CIS gauge is no longer on back order from JC Whitney. Then i can configure it to the proper control pressures.

Good luck and let us know how you make out.

while you are waiting for your gauge to arrive, a great book to read to understand the fuel injection system and troubleshooting is "bosch fuel injection and engine management" by charles o. probst. have fun.

roger

See this thread:

http://forums.pelicanparts.com/porsche-911-technical-forum/292473-anyone-try-cis-tester.html

And this one:

http://forums.pelicanparts.com/porsche-911-technical-forum/292431-cis-pressure-tester-plans.html

Here are the results. I would highly recommend this easy repair and a viable and cheap alternative to buying a refurbished WUR (only $10 in parts, including the 10-32 tap). After acquiring all the materials, this modification only took 90 minutes of my time to complete.

Step 1) Checked resistances of heating element. As you can see, I also opened the WUR and the heating element looks to be in great shape.

http://forums.pelicanparts.com/uploa...1152574848.jpg

Step 2) Drilled and tapped plug hole with #21 drill bit and tapped with 10-32 threaded tap. Also drilled smaller (3/64) hole for locking pin, to prevent the plug from turning.

http://forums.pelicanparts.com/uploa...1152574925.jpg

http://forums.pelicanparts.com/uploa...1152574972.jpg

Step 3) Cut pin and threaded rod to proper length and reassembled.

http://forums.pelicanparts.com/uploa...1152575013.jpg


Now I am waiting for the CIS gauges to arrive to finally tune the pressures.

Now that i have made my adjustable WUR and await my CIS gauges. Can anyone tell me what control pressures this should be tuned to? I have a '78 SC ROW.

bump.

Cold (20C) 1.6 to 2.05 bar, 25C 2.2 to 2.65 bar. Warm w/ vacuum attached 3.2 to 3.6 bar, vac line removed 2.7 to 3.1 bar.

My two cents...

If you can do what you're doing by customizing your system...thumbs up to you. My experience with the WUR is that while yes you can swap WUR's from different years without issues, re-built WURS are hit and miss. Mine was re-built by Python. I hear Python is a good company but my WUR went out within 8 months of installing it. Since it's a daily driver I now get the excessive vibration because of the missing issue while I drive it and the nuts and bolts on the car are loosening up a little and I'm getting some oil leaks here and there. (oil sump cover...etc)So....now I gotta get back in there and tighten everything up again....

Anyway...I just decided to order a brand new one from Bosche. And now I hear they (OEM) are phasing out parts for the older models....so now what? How long before we can't get these parts anymore?... We need a great after market manufacturer to step up and give us some quality parts, otherwise we are all going to have to customize our engines and or upgrade to newer. I myself am considering the EFI kit.

I hope I didn't hijack this thread...but crap.

I post this only as an alternative, no offense to Pelican and our host.

Great set, fast delivery and no tax if not in NV.


mytoolstore.com

The WUR is a fairly simple device. Seems to me the wear part would be the diaphram. I haven't seen any posts on removing / replacing that part. Do the rebuilders have a source for parts such as diaphrams, springs, bi-metal arms and heating elements or or they swapping used parts from donors??

That's the one I just bought about 2 months ago. I like it and it wasn't on backorder!!

I have my gauge all setup and i took my first cold control pressure measurement. It leveled out at 1.6bar, which i think is a little low. What should i expect it to be? The ambient temperature here is 83F or 28C.

Around 2.3 bar..you need to look at the graph below for your WUR/car.
http://forums.pelicanparts.com/uploa...1154443318.jpg

Ron,
Thanks! Im going to go out and set the pressures now.

You also need about 0,5 bar of vacuum to meassure...