Partial Power Loss to Engine Failure in the Pattern

[Ragsf15e]

1 hour ago, AerostarDriver said:

All throttle changes I am doing are reactionary to the RPM decay and the MP increasing. Base and final you can see the EGTs just drop away every time MP increases. 

One thing to consider… and I’m just throwing this out there because it’s impossible to tell exactly what caused what… when you lean it back pretty far and then add power, the engine may stumble and/or die.  It will run at low power with the mixture much farther back than it will tolerate at higher power.  I’m not saying you leaning it caused this because I wasn’t there, but it’s something to consider.

[EricJ]

Something to check while you're poking at it is the braided fuel line that goes from the servo to the flow divider.   There have been reports of those deteriorating/collapsing/failing and causing problems.   You'll have to disconnect that to take the servo out, anyway, so it's just another thing that's reasonably easy to check.

 

[David Lloyd]

Is that the original MP gauge?  Indications look a little odd in that 20-25" is a larger arc than older factory gauges.  Also, it is obvious with the instant wide variations there is no snubber in the line.  No way mine could be made to jump around like that.  Shouldn't cause a problem, just one more thing to check at a later time.

The fuel injector servo will do it's job from 15psi or less up to 50-60 psi.  Like some other things, Mooney had to select a red line and because the mechanical pump they used was from about 24-27psi, Mooney (and others) chose 30 as a red line.  Shouldn't cause a problem, just one more thing to check at a later time.

Fuel stain/leak at the bottom back of the engine cowling needs to be investigated before running again.  Fire on the ground is ugly.  Worse in-flight.  I have seen leaking hoses, leaking tubes, loose b-nuts, ruptured mechanical fuel pump diaphragms, leaking servos, leaking spiders, broken injector lines.

All the above may be unrelated to the engine losing power.  I suspect the fuel servo.

[PT20J]

For the IO-360 series, Lycoming specifies a maximum fuel pressure of 45 psi and a minimum of 14 psi. 

EDIT: I note the above only to point out that the engine should likely operate normally with a fuel pressure of 36 psi. However, normal is more in the range of 25 and Mooney's limitations take precedence over Lycoming's when the engine is installed in a Mooney.

[AerostarDriver]

Had one of the recommended on field A&Ps take a look. After some talking and dissection, we found what we believe is the culprit, a stuck poppet valve was allowing unmettered fuel flow to the metered side of the fuel servo. The only way to get the engine running was with the mixture in the full lean condition. The fuel leak was driven by a new intake gasket leak that had fuel dripping down the tube to the oil sump then down to the fuel servo. 

[carusoam]

Great follow-up AerostarD!

Nice work bringing her down…

If you want to share JPI data…

Go to the Savvy website… upload the data there, hit the share button, copy the link here…

The video is really good.

The data can be really helpful to support the video…

If you have FF data going into the JPI… that would really show a sign…

Best regards,

-a-

[AerostarDriver]

Some photos from inside the fuel servo.

[carusoam]

Kinda looks like corrosion from here?

That would cause some stickiness…

Best regards,

-a-