BMW Z3 fuel system faults
Z3: how do you release the fuel line quick connector?
Push the plastic sleeve all the way in, and the connector comes off like a compressed-air coupling. The sleeve is not pulled up. A rusty or oxidised connector can jam, in which case it has to be twisted and tugged. On the fuel filter connectors, press the connector and the locking ring toward the filter.
Z3: how do you release fuel pressure before opening the connectors?
Pressure can be released from the valve on the fuel tank. Another way is to remove the fuel pump fuse and let the engine stall on its own. This way no fuel sprays out when the lines are opened.
Z3: why does the fuel tank go into vacuum or leak fuel?
The vacuum can be caused by a blocked vent hose that runs from behind the tank to the charcoal canister (vapour collection canister). The blockage may have been sand. A leak from under the engine bay can come from a hose that has come off the fuel filter.