I am not fluent in electrical diagram but I can follow some.
I have many diagrams spread out all over the floor to help me with installing an L Jet system in my notch back.
I have two wires on the dual relay pump section connector. One black, circuit 15 I believe is keyed hot, and attaches to the coil.
The other wire is yellow and it looks like to me it runs off the circuit that kicks the solenoid on the starter and is a temporary on circuit. Is this correct or is circuit 50 also always on?
Thanks for any help.

On the 914, the yellow wire goes from the ignition key to the bendix of the starter and is momentary on when the engine is started.

Out of curiosity why would the fuel pump relay need a momentary power source?

Safety, when the engine quits running for whatever reason, power is removed from the fuel pump

All the D-jet cars ran the fuel pump for a few seconds when the key is first turned on to prime the fuel circuit and then switched on the pump when there was and ignition pulse.

For L-jet the pump is first powered up when you start cranking by that starter circuit voltage at the double relay. Then as the engine starts up the flap in the air flow meter moves enough and the air flow meter switches power to the double relay to keep the pump powered.
If the engine dies for some reason, the air flap closes and shuts off the pump.

Jim