Even though we call them "lift" pumps they should actually be called "transfer" pumps. They work on flow not pressure.

The injection pump is really a compressor with timed release valves (the line outlets).

Transfer pumps generally deliver X amount of fuel at less than 5 psi. As was pointed out in the previous post, any excess pressure is vented into the return line.

You can increase the pressure from the pump with internal adjustment which of course means you have to change the nozzles and readjust them or you could just have the pump and nozzles caliberated to each other. For peak ultimate performance that is the way to go.