I've never owned one but have helped friends in the distant past. My 911 is a CIS car and I know that system well.
Here's a link to a manual explaining all the parts (sadly no troubleshooting guide):
http://www.berlinasportivo.com/Technical/lancia/Thema832/Bosch-KE-Jetronic-OCR.pdf
My understanding of the KE-Jetronic is that it's essentially the same principle as the K-Jetronic with a couple of changes:
- No WUR - The fuel pressure regulator is essentially fixed with some modulation from manifold pressure.
- The pressure regulator in the fuel distributor is now the adjustable bit and is what the ECU modulates to achieve the right mixture.
I think this means that pressure tests are a little backwards from the regular CIS cars (K-Jetronic).
What pressure did you measure in the lower chamber? And what did you measure for primary pressure?
The fuel distributor is still subject to all the same issues with old fuel. My initial thought is to make sure the tank has just a couple of fresh gallons of ethanol-free gas and a can of SeaFoam, circulate the fuel through the system, let it sit a day, and repeat. This might free up the fuel distributor.
Another thought may be to remove an injector, run the fuel pump, raise the plate, and make sure you have fuel coming out. Maybe you don't have enough lower chamber pressure to open the injectors.