Well, after some missteps, I now have some pressures that look ok, as follows:
Cold cp: 2.0-2.1 bar
Warm cp: 3.72 bar after 5 min
System pressure: 6.4 bar
Along the way I decided to test some relays. All the red and black round relays tested good. However, the yellow relay on the left side behind the cover appears to be dead. When I apply +12v to 86 and Gound to 85, I get no clicking which i hear with the other relays. What are the symptoms of a failed yellow relay? Checking quickly I see Pelican’s price for this relay is over $300, it must be gold inside.
Another thing i noticed is that there is a sensor with a red plastic boot in the intake manifold and there is no wire on the GND terminal and no evidence of a disconnected wire in the vicinity, see below:
Perhaps it is grounded through the body of the sensor to the intake? Should I run another GND wire to that terminal?
I also recalled (hasn’t happened lately) that it occasionally backfired during cranking. Afterwards it would not start for 30-45 minutes but then it would start and run normally. Any thoughts why it wouldn’t start until 30-45 minutes? Perhaps connected to my other “stumbling” symptom that started this thread.
I went to check the rotor but wasn’t sure how to access the rear clip on the distributor. Is a rotor failure visually detectable?
Anyway, I still need to check that the timing advances correctly. I presume that now that the control pressures are verified ok, that rules out other fuel supply issues related to the fuel system, such as fuel filter and fuel accumulator?
I wanted to test fuel pressure in the manner shown in the WSM but the special Porsche tool to connect the gauges to the rear fuel pump is not available anywhere that i could find.
Anyway thanks in advance for your feedback.