Just wanted to share this with you. Finished up my Annual. Noticed
fuel leaking around top "dome" of mechanical fuel pump when I turned
on my backup electric pump. Also electric pump would not "pressurize"
as normal. (engine not running). Looked carefully at the securing bolt
on top of the F/P dome. Yes the helicoil threads had stripped out of
the F/P base. This problem apparently had been getting worse over
time but apparently always had enough threads for proper torqueing
down the "dome" top of the F/P. My mechanic and I should have been
looking more carefully at the fuel pump threads for wear. Engine is 40
yrs old with only 750 hrs TT but pulling off the fuel pump top to
inspect the fuel screen over many years caused a failure of the
helicoil (threads) little by little until nothing left to grab onto.
Another factor was changing out the bolt for a newer looking one but
was maybe 1/16 in shorter. This added to the eventual failure. Luck I
was not in the air or most certainly the cap would have popped off.
This is a good reason to change out an old F/P if threads don't look
so good. Bolt had never been cross threaded but just stripped out the
base threads due to age and maybe a little overtorquing. Just a
safety tip for you to think about.

Larry