Hi Geza,

Fuel starvation makes the pump heat up, as it is not being cooled by
the fuel flowing through it. At the same time it is also being asked
to work harder to pull fuel. Ever hold the shaft of an electric motor
still while applying power to it? (drill or power saw, for instance)
Electric motors hate that, and they will make noise to tell you about
it. That's what your fuel pump is doing.

The heat and extra stress will soon wear out the bearings in the
pump, and thereafter the pump will be loud regardless of whether the
fuel is flowing freely to it.

If you resolve a starvation condition early enough your pump should
return to silent operation. If it doesn't, then you should consider
carrying a spare before venturing on any long trips away from
mechanical assistance. It might keep going ok for years, or perhaps
not. If it were my bus I'd change it out and carry the noisy unit as
a spare in case someone else's failed. YMMV.

Happy Trails,

Greg Potts
1973/74/75/77/79 Westfakia "Bob the Tomato"
www.pottsfamily.ca/westfakia
www.busesofthecorn.com

On 16-Dec-06, at 11:26 AM, Geza Polony wrote:

> What I'm still not getting is how you can replace a fuel pump and
> still have
> it make the buzzing sound. The consensus in the archives seems to
> be that
> there are two causes for FP buzz syndrome: fuel starvation, either
> because
> of a clogged filter or because of a clogged fuel line before the
> filter, or
> bad pump bearings caused by the fuel starvation. How could "fuel
> starvation"
> make the same sound as a bad bearing? And how can you tell?