1996 Chevy p/u 5.7L eng. . seems to be loosening fuel pressure at start-up what can i do?

When the engine is off and you turn the key the key to the "on" position, the fuel pump should come on for a few seconds and pressurize the line. Actually, when you turn the vehicle off it really shouldn't lose much pressure anyway. But the fuel pump will always come on for a couple of seconds when the key is in the "on" position.

First thing I would check is the fuel pump relay. It should be in the fuse/relay box under the hood.. try switching it with another similar style relay (like the A/C relay for example) and see if that fixes it.

could be a number of things, possibly fualt in the fuel pump causing it to not egauge when you turn the key and it is taking a few goes the start pumping. if this is so as time goes on it will get worse untill it fails all together. check for a blocked fuel filter if it hasnt been changed recently. also check that the pump is getting power when the key is turned, do this by using a test light on the powerwire at the pump and have some1 turn the key on and off repetedly, making sure the like goes on and off every time. if it acasionaly does not light then it could be a wiring issue, proccess of elimination!

Could be many things, first thing I would do is seek a professionals help, aka a reputable repair facility for a proper diagnosis.