Its not a 'ground' problem as the injectors are 'grounded' by the ecu. (I think). Seems the ecu is holding all injectors open. On my RHD E28 735i the ecu is behind right front kick panel.
Try disconnecting battery terminals and joining them (the car wires - not the battery terminals) together for 10 mins (have a coffee). That might reset the emu. If not then down to the salvage for a unit. If you get stuck mail me on this site. Also get the injectors out and cleaned on a rig - they might be leaking. Change the fuel filter and flush the lines.