I've had a loud fuel pump in my '85 for Years an never found the problem. I've replaced the fuel pump (6 times) ( with know good ones), the fuel tank, filter, all lines, and even the wiring. 
I gave up and accepted it. I've know this problem to happen to others that also went Unsolved. 

Best of luck

-craig

Sent from my iPhone

On Jan 5, 2012, at 8:49 PM, Steven Shelton <shelton4@GMAIL.COM> wrote:

> In response to my previous email concerning a buzzing noise from the fuel
> pump on my '85 camper, the consensus was that it most likely was a clogged
> filter or fuel tank inlet screen.  A little more background:  In February
> 2011 I replaced all the fuel lines and "upgraded" to the canister type
> filter, which is installed on the outlet side of the pump.  In June I
> jolted the van when I hit a dip in the road.  The engine died and would not
> start.  I had it towed to the local dealership and they said it was the
> fuel pump, so they replaced it.  A couple of months ago an intermittent
> buzzing sound started but I couldn't trace it to the pump until about three
> weeks ago.  Anyway, I bought a new fuel filter and while installing it went
> ahead and removed the pump to look at it.  I tapped the pump inlet on a 2X4
> and a good amount of grit came out.  I rinsed it out as well as I could.  I
> decided that the old box type fuel filter, which is installed on the inlet
> side of the pump, is actually better because it prevents grit from getting
> into the pump.  I installed a new box type filter and kept the canister
> filter, too.  The pump still buzzes.  Since the box type filter is
> translucent plastic, I was able to shine a light on it and it looks like
> something is moving through it, maybe air.  How can air get into the fuel
> line?  If this is a clogged inlet screen, how do I clean it and why does
> the van run fine at any speed when it should be starved for fuel?