Hey Yoni, It sounds like your static fuel pressure is bleeding down after the car has been parked for a while. The CIS mechanical injection system should hold a fixed supply of static fuel pressure in preparation to restart the engine between a check valve screwed into the fuel pump and a parallel circuit that includes the fuel accumulator, a cold start injector and the 8 cylinder intake injectors. Your symptoms may indicate that one of these components is allowing the static pressure to slowly bleed off at engine shut down. Check the static fuel pressure after the car has sat for a while.
As a temporarily fix, you can jumper your fuel pump relay (pins 30 and 87) to provide power directly to the pump which will reestablish the needed pressure and easily allow you to restart your engine. The procedure you are currently using (holding the accelerator to the floor) will flood the engine every time.
One other comment - If the static pressure is bleeding off at the fuel pump - some of the early pumps integrated the check valve into the output port of the fuel pump. You may have to replace the fuel pump with a later year model that has a replaceable check valve. (I have seen where some owners with the early style fuel pump have added a new Bosch check valve (stacked in series) onto the built in check valve output port)
Good Luck, Michael
