IO-540 mystery

Paul Tomblin wrote:
Twice this year, while people have been flight training in it (I was
doing a BFR this spring, another pilot was checking out in the plane
for the first time a few weeks ago), the engine has been running fine
and on rollout afterwards the engine died and couldn't be restarting.

Disclaimer: This is based on experience with ground vehicles and
equipment. I don't have an A&P; I don't even have a TG&Y. Your
mileage may vary.

My first thought is as others have suggested: fuel pressure, pressure
regulator, etc. The testing that has been done has somewhat addressed
this. It may be worthwhile to check how the pressure regulation gets
feedback on the engine load. Many cars, for instance, have a vacuum
hose from manifold vacuum to the fuel pressure regulator. If this hose
has a crack or leak, or is plugged, it can affect the fuel pressure - it
might always be wrong, or it might be slow to respond to engine load
changes.

My second thought: is the tank venting OK? If a vent line is pinched
off, or if somebody installed the wrong filler cap or cap gasket on the
fuel tank(s), the pump ends up trying to suck on a bottle (and failing)
sometimes. Maybe it's something like fuel getting into the low spot
on a vent hose during a bank, which is why it doesn't always show up.

Disclaimer: This is based on experience with ground vehicles and
equipment. I don't have an A&P; I don't even have a TG&Y. Your
mileage may vary.

Matt Roberds

writes:

It may be worthwhile to check how the pressure regulation gets feedback
on the engine load. Many cars, for instance, have a vacuum hose from
manifold vacuum to the fuel pressure regulator.

That's because the fuel pressure is regulated to be X psi above the
intake manifold pressure, not above atmosphere.

[I also have NoKlue if that's true on aircraft; whose FI systems
seemingly date from the Neolithic era of combustion history...]
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