Fuel pump cooling shroud?

[Jim Burns]

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

[Ronnie]

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
>
>

[[email protected]]

Most Piper small singles (PA28's) have exactly such a cooling shroud
around their mechanical fuel pumps. Perhaps you could talk you A&P into
installing them on your Aztec as a minor alteration?

[Jim Burns[_1_]]

I could try, but I think "engine cooling and baffeling" is specifically
spelled out as a major alteration in the AC of 337 instructions. The ram
air source for the shroud would require a hole through the rear baffles.
Jim

> wrote in message
oups.com...
> Most Piper small singles (PA28's) have exactly such a cooling shroud
> around their mechanical fuel pumps. Perhaps you could talk you A&P into
> installing them on your Aztec as a minor alteration?
>