denaliano, on the 124 cars the FPR vent line connects to the bottom of the air cleaner breather hose which attaches to the valve cover. As mentioned if the FPR diaphragm ruptures the vent line directs gas to the valve cover instead of dumping it on top of a hot engine and causing an underhood fire.

It's possible that putting a vacuum on the diaphragm ruined it. Best to verify that the diaphragm is intact before installing a faulty FPR.

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Fred Hoelzle