What he said...
Whether the pressure builds up or not, the pump cycle is just a few seconds at the most. If it does not prime the first time, you can cycle the key between OFF and ON several times. But the pump stops on cue, pressure or not.
If the pump is new, then perhaps it's either defective (probably a common issue these days), there is an air-leak in the lines, or there is not enough fuel in the tank to start the siphoning.
How much gas is in the tank?
If it's an older pump, then it won't have liked to have been left sitting for long. If it was even just slightly used (a few thousand miles) and then was left to sit for three or four months, or longer, then the pump may have simply died an early death. They absolutely hate sitting unused in today's modern fuels with today's crappy pumps.
But the pump running constantly under computer control (or a lack thereof) leaves a high probability of bad capacitors at the very least.
Is it a new computer? A parts tore re-furb? One just recently re-done by Garry? If re-done that would be extremely unusual for it to be bad at first startup. Don't remember if that's ever happened here before in fact.
But if it was an older ECM and was just re-flashed for your use, it's entirely possible the capacitors were borderline already and simply didn't make the trip back and forth. I assume if they were bad before ten it would have shown up during testing unless a fuel pump circuit test was not part of the normal process.
On other forums there have been a rash of store-bought ECM's that didn't work right out of the box, and the replacements were bad within weeks, if not days. Not always the three main capacitors, but more often than not.
Paul
