That is a good analysis. How to verify the cause of an intermittent long crank and a start/stall condition. No need to have the electronics as shown first (because we backyard mechanics do not have them anyway), just remove the vacuum hose and sniff if there is fuel smell or even fuel coming out. Watch for fuel. Takes over a minute that fuel is coming out of the port in this vid, diaphragm cracked.
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I wasn't that patient to wait that long on my E32 750iL which has 2 fuel pressure regulators, have to test again.
To be on the safe side, I would connect on the fuel pressure vacuum connector a transparent hose and lead it out of engine bay into a container/bottle, just in case a lot of fuel is splashing out.