Jim,

We don't have these on our pumps on our Aztec.

I had the left mechanical fuel pump fail during takeoff
and the engine surged until I got the boost pump on
(yes, I know, it should have been on before).

The failed unit had a split in one of the folds in the
rubber diaphram about 3/4 of the way around. It
could keep the engine running in cruise, but not when
full power was called for.

I wrote my failure off to old age. From the logs, it appears
that the pump was more than 20 years old, so I figured it was
way past time for the rubber diaphram.

Ronnie

"Jim Burns" wrote in message
...
Recently we had to replace one of the mechanical fuel pumps on our Aztec
due to a leaking diaphragm.
When talking to several A&P's about the expected life of these pumps and
the cause of failure, most sited heat transfer from the accessory case to
the pump and lack of cooling being the primary culprits. Some A&P's
recommended turning the vac pump outlet to direct air onto the top of the
pump, others said that the fuel flowing through the pump should cool it
until you shut the engine down, then the pump absorbs the engine heat and
cooks the rubber diaphragm.

Not that it would help after engine shut down but I ran across this on
ebay today... http://makeashorterlink.com/?T297322BD Does anybody in the
group have such a shroud on their fuel pump? Aircraft Make/model?
Thanks
Jim