LS1 fuel pump prime intermittent

[lux]

My 72' has a LS1 swap with a fuel pump priming problem.
On occasion after driving for a while and switching the engine off for a while it will not start. It turns over fine but I don't hear the usual fuel pump priming that I get when switching the key on.
This has happened on thee occasions. After towing the truck home and letting it sit for a while it starts just fine.
I thought it might be wiring to the fuel pump and I checked it all. I found one questionable connection and fixed it, but I guess that wasn't the real problem because it happened again.