Please help me!!!

When you put the key to the accessory position the fule pump turns on you here a hissing sound out side. Now when you do that it turns on some times. When the care is started it feels like the pump is flickering on and off as you drive what I meen is that the motor is getting a lack of fule. Some times it gets some and sometimes it dosen't. Does any one know what the problem may be.

Here is what I checked: the fuel pump connection under the back seat and the relay under the dash above your legs.

Bob Balafas