Weird FASS Noise

[DaveHess]

I fired the Ram up yesterday after it sat for the past 19 days in the garage (my medical reasons). She fired right up and all the gauges looked normal. Drove it in city driving for about 30 minutes and shut it down outside a buddy's shop. When I was ready to leave about an hour later, I went outside and started the truck to let it warm up (41 degrees ambient temp) for a couple of minutes. When I exited the cab, I heard a "hissing" noise coming from the general area where the FASS is mounted under the bed. It was loud enough to be heard walking past the bed. I looked on the ground and it was dry with no signs of anything dripping, spraying or running on the ground. Checked my fuel pressure and rail pressure and they were at 18psi and 5K respectively at idle. Drove home and parked in the driveway. About 6 hours later, fired it up, checked the fuel gauges again. Normal. Got out and the "hissing" was still there. Crawled under the truck and the noise is definately from the FASS "area". I could not directly locate the source however. I put my ear to the filter and water separator and both had a steady humming noise to them. I touched all the hoses, filter, water separator, and pump. All had a "hum" (slight vibration) feel to them. Nothing seemed out of the ordinary. The pump was slightly warm to the touch. More importantly, everything is bone dry. I checked all my fuel lines to insure no pinching. I checked the tank and return line connection. Everything appeared normal. Put the truck in the garage.



20 minutes later couldn't stand not knowing anymore and turned the ignition to "on". Crawled back under and still could not locate the exact location. It is definately right there where the FASS is. Shut it down. Putzed around for about another 20 minutes and did this test again, this time it was quiet with the exception of the normal hum of the pump.



Anyone out there had this happen or have any guesses???