Diagnosing CIS Components from Pressure Test
 

Overview:
Hey Everyone, thanks in advance for any help. It was one of the first warm days in Michigan this previous week so I thought that I would try to take my car out for a spin (78 911SC). Unfortunately when I tried to start it, it was just cranking but not firing. After a few attempts, I decided to give my starter a break and when I stopped cranking I heard a few weak coughs from the engine. After about half an hour, I tried to start it again and it reluctantly started. Once it warmed up, I pulled it out and swung around the block to the gas station where on the way, my car would stall between gear changes and at the stop light. This was after the revs came down from about 25-3000 during acceleration and the stall seemed to be the result of the engine not catching itself at idle speed. I will try to be as detailed as possible for post efficiency. Thanks for any help!

What i've tried:
When I got home, I took off the heater pipes and tried to look for any obvious air leaks. I sprayed some carb cleaner around the injectors and intake boot, etc with no change in idle. After the car was running for a little bit, I took off the oil cap and noticed that the idle dropped 1-200 RPM. I then took out the air filter and tried to see if the field test with the air plate uncovered anything but it seemed to run rougher as i lifted the plate. Decided to move on from the mixture for now and do a pressure test.

CIS Pressure Test and Results:
1) Jumped Fuel Pump Relay

2) Connected the pressure gauge between fuel distributor and warm up regulator (Ball valve on the WUR side)

3) Unplugged WUR

4) With Ball Valve closed, started fuel pump : System Pressure = 75PSI (5.17 Bar)

5) Opened Ball Valve : Cold Control Pressure = 12 PSI (0.69 Bar)

6) Plugged WUR in, Recorded Pressure at times below:
1 Min = 12 PSI (0.82 Bar)
2 Min = 18 PSI (1.24 Bar)
3 Min = 22 PSI (1.52 Bar)
4 Min = 25.5 PSI (1.76 Bar)

7) Stopped Fuel Pump, Recorded Pressure at times below:
0 Min = 28 PSI (1.93 Bar)
10 Min = 24.5 PSI (1.69 Bar)
20 Min = 23 PSI (1.59 Bar)
30 Min = 22 PSI (1.52 Bar)

Notes: From looking at the graphs on the CIS primer page, it looks like my cold control pressure is below spec. Am I correct in thinking that the WUR may have gone bad over the winter storage?

The Temp when I performed these tests was 44F in Detroit, MI.

I am unfortunately not sure the WUR model number. I did however notice that it has a second vacuum port out of the drivers side of the WUR. (Away from center of engine). I don't want to replace the WUR until I can verify the correct model number (if that's even the problem here)

Thanks, let me know if there's any other info you might need!

-Joe