Diagnosing CIS Components from Pressure Test

[JoeyD1005]

Hey Everyone,

First off thank you for any help in advance, I've been doing quite a bit of reading and I'd like to try and provide as much information as possible for what I'm hoping is an easy diagnosis.

Car: 1978 Porsche 911SC

Background : First nice day rolled around in Michigan and I was going to try and take my car out for a drive. Unfortunately, I was having some trouble starting it. For the first few attempts, the car cranked but wouldn't start. After cranking for some time, it would kind of have a very weak burp type of a fire after I stopped cranking. With no luck after a few tries, I gave my starter a break and said I'll come back to it. After about 30 mins, the car reluctantly started and I let it warm up. Pulled out of the garage, seemed to be running a little rough but thought it could just be because it was stored all winter on bad gas so I ran to the sation up the street for some 93. On the way there, the car died twice at a light and I had to keep revs up with the car in neutral at lights and breaking. Got it home and started doing some research.

What I've Done So Far: Upon some general reading I decided to perform some general vacuum leaks. To do this, I uninstalled some of the heater piping so that I could spray some carb cleaner around the injectors and airbox. No change in idle.

Once the car has warmed up for some, I removed the oil cap and the idles dropped 1-200 ish RPM and the idle became a bit rougher.

Took out the air filter and tried to see if there was any sign of mixture related issues by doing the field test with the air plate. Seemed generally to be right in the middle of rich surge and lean. Decided not to even mess with mixture to keep variables in check. On to the CIS pressure test.

CIS Pressure Test Procedure and Measurements:

1)Connected Fuel Guage between Fuel Distributor and WUR (Ball Valve on WUR Side of T Fitting)
2)Jumped FP Relay Socket
3) With Ball Valve Closed, ran Fuel Pump : System Pressure read 75 PSI (5.17Bar)
4) Opened Ball Valve w/ WUR Unplugged : Cold Control Pressure read 12 PSI (0.69Bar)
5) Kept Ball Valve open and plugged WUR connector back in:
- 1 Min Reading : 12 PSI (0.82Bar)
- 2 Min Reading : 18 PSI (1.24 Bar)
- 3 Min Reading : 22 PSI (1.52 Bar)
- 4 Min Reading : 25.5 PSI (1.76 Bar)
6) Kept Ball Valve Open and Shut off Fuel Pump:
- 0 Min Reading : 28 PSI (1.93 Bar)
- 10 Min Reading : 24.5 PSI (1.69 Bar)
- 20 Min Reading : 23 PSI (1.59 Bar)
- 30 Min Reading : 22 PSI (1.52 Bar)



Notes: I ran this test with NO vacuum to the WUR. I am not sure if that is something that is required on this year. I unfortunately am not able to see from where I looked any sort of part number designation for the WUR from where I checked. Between the top vacuum line and the electrical connector I only see the word BOSCH. I did however see that there is a vacuum line off the drivers side of the WUR (away from center of engine) that does not have any vacuum cap or line that has fallen off.

From what I have read on the CIS Primer site, it looks as though my WUR control pressures are lower than what is expected by the system. Am I correct in suspecting that this is my main problem?

Please let me know if there is any more info needed for the discussion, I will try to get it asap.

Thank you again!
-Joe