The Porsche 928 continuous injection system is very robust when properly set up. However, it requires clean fuel and pressures set to the correct specifications.
This 6 page procedure is designed to guide you through setting a baseline fuel tune on your early 928 with Bosch K-Jetronic CIS.
Primary focus is to help you get a non-running 928 to start and idle again, especially when it has sat for a long time. Also, it may be useful to set a new baseline after extensive engine service has been performed on your 928.