You didn't mention what type/brand EFI you installed.
You mentioned you normally hear the fuel pump humm a few seconds after key-on which would describe a returnless system. Typically relies on a pressure switch.
Do you have pressure gauge on the fuel rail?
Try cracking a line at the fuel rail to see if you already have pressure there. (have a rag under the fitting be ready to grab the fitting with the rag to catch any spray.)
Sometimes an intank pump can hi-side and produce too much fuel and flood your plugs. You might pull one to check.
A set of piercing probes are handy for checking power and ground in active circuits.
https://www.amazon.com/Goupchn-Insul...316302&sr=8-11