FASS has been in for a day now. So far fuel mileage has dropped by about 1 mpg, truck runs rough sometimes, and this thing is getting louder all the time. Is any of this normal? I'm hopeing this is a phase that happens with new units. Nothing underneath is leaking and acceleration is about the same as before. Fuel filter is already getting rock chips in it too. pretty soon it will look as bad as my paint. Anyone with a FASS please chime in here.

 

Fuel mileage should not drop. The fuel filter will only show rock chips until the paint is gone You must have an air leak, with air they get louder. Mine still sounds the same as it did the day I put it on.

 

Do you have a fuel pressure gauge? If so, what are your pressures like? That will be a good indication as to whether you have a real problem or not, although it sounds like you do. Suggest you call DPP on Monday if you haven't already. They can better tell you what is normal and what is not. Rock chips, yeah, here to. Go to Home Depot in the PVC pipe section and pick up a couple of rubber 3" pipe couplers. They come with clamps. The rubber couplers slip right over the filter and water separator. Rocks bounce off instead of dent. You will need four couplers, two for each.

My fuel mileage stayed the same and the truck runs smooth. I could swear it is getting louder though, but I may just be getting use to it. It is not a smooth running pump. I can hear what sounds like big air pockets hitting the motor, causing cavitation from time to time. Seems to be smooth running when the truck is sitting still idling, but move the truck at all, even just stepping up to the drivers seat, and it sounds like a big air pocket coming loose from somewhere and going through the pump. I have already gotten rid of the quick disconnect at the tank thinking I was getting in air at the fitting since it was really loose. It seemed to help a little, but not completely gone. As bad as the pump sounds when a big air pocket hits it, it can't be that way by design because it doesn't sound good. Time will tell. Two year warranty. I have asked DPP about it and they said it sounds normal, but I'm thinking maybe I didn't describe it well enough, because it sounds narley.

 

I'm hopeing it is just air. Like I said performance is at least the same, but I was expecting better fuel mileage not worse. And at times I'm getting a lot of vibration. My foot was falling asleep from touching the accelerator pedal and once in awhile the truck was hesitating off idle. Guess I'll have to add a fuel presssure guage to my list. Thanks for the responses so far. Any more ideas or reporting similar problems is appreciated.

 

Noise has begun to quiet down some. Might of had air in the lines. Mileage though has not improved much as of yet, and power levels are the same as before.

 

The fuel circulates too fast to not get the air out right away. You must still have a leak. Double check everything and use two clamps on the hoses. And try keeping your tank full for a week.

 

The mileage problem may be that winter fuel is probably coming out now. I notice a big difference when they change fuel. Mine has been on since last winter and I don't even notice it any more.

 

I finally had all I could take. The noise had gotten to the point of being ridiculous. I got a hold of Brad at DPP and explained everything to him again. He asked me to do a test, taking the return line loose and putting it in a bucket then bumping the starter to fill the bucket with fuel. Then take the suction line loose and drawl fuel from the bucket, basically taking the fuel tank out of the equation. When I did that, it made no difference in the noise, so he said it sounds like I have a bad FASS and shipped me a new one. If the noise had stopped, then the culprit would have been a smaller diameter pick-up tube that have been popping up in some 3rd Gens for no apparent reason.

It really sucks that I have to swap it, but the customer service from FASS was great and shipping me a new one without requiring me to take this one off first. I wish some of the other aftermarket vendors were as easy to work with. If I hear back on what was wrong with it, I'll post it.

 

this might answer some of your question, a couple posts down

https://www.dieseltruckresource.com/...hlight=f.a.s.s

 

yeah mine is loud and obnoxious too and i've heard of bearings going out. talked to brad and he said bucket test and see i blew out the lines last night and it seemed better for a bit but I wish that i would have known i would have to drop the tank and cut screens out or whatever else i have to do in conjuction with the product doing it's designed task sufficiently