I lost the gas cap from my '06 PA and had trouble finding a replacement that fit. Since the filler pipe itself looked rusty and the hoses old, I found a replacement filler neck at GMPartsGiant.com, part #15721334.
I decided it would be another thing I'd replace while I was at it. I'd also put in new sections of the 2 hoses (fuel & vent) while I was at it. Simple enough job, right?
I bought new hoses and clamps at NAPA sized to match the pipe ends on the new filler neck. Since the old sections of hose were clamped onto both the old filler neck and the next downstream section of pipe, I ASSUMED both pipes were the same size. WRONG!! The old fuel line hose was actually 2" and I had bought 1 3/4" which fit fine on the filler neck. After much struggling and expressing my awe of Fleetwood manufacturing while trying to shove the undersized hose into place, I gave up and went back to NAPA to purchase another couple of feet of amazingly expensive 2" ID fuel hose.
Now you may rightly wonder how 2" ID hose is going to work on the 1 3/4" OD filler neck on the other end. I hadn't really noticed when I removed the old filler neck, but the neck itself begins as a 2" pipe and then narrows (WHY??) to the smaller diameter. The original 2" hose had been shoved all the way up onto the 2" part of the neck, even though there's no detent ring up that far for securing the hose clamp. Oh well, I guess since it isn't a pressurized line there's no worry about it. So I did what Fleetwood did and clamped it at the 2" section. I don't think it's going anywhere.
The vent line had something of the same problem, but the size difference wasn't as great. So I was able (with more verbal compliments for Fleetwood) to shove enough of the 5/8" hose onto the downstream vent pipe to get a clamp on it. Whew! Hard part done.
But... there's still the matter of fastening the collar of the filler neck to the fiberglass. On that collar (the OEM and the replacement) there are pre-drilled holes at 3 & 6 o'clock. Admittedly they're too small and would have needed to be enlarged for securing the neck, but Fleetwood decided to ignore them and place screws at about 2, 6, & 10 o'clock. Fair enough it would seem, but as it happens the collar on the neck is not continuous. There is no collar material below a horizontal line tangent to the bottom of the filler pipe. In other words, the screw placed into the fiberglass at the 6 o'clock position penetrated no part of the collar and SERVED NO PURPOSE WHATSOEVER.
So I'll drill one or two extra holes besides the 2 upper ones Fleetwood already made just to tighten things up a bit. I'm also using bolts, washers, and nylon locknuts instead of the original screws. I don't want to mess with this part of the coach again.
Oh yeah, and the gas cap that GMPartsGiant.com said would work with the filler neck didn't. I finally got one that fits at NAPA (part #703-1722, non-locking).