Are These Problems Related?

[Rob58]

On run-up today found two serious problems: big 250 rpm right mag drop (very rough running) and no vacuum. Lycoming O-360. I don't believe in this kind of coincidence so I am trying to figure out if there is any way these problems could be related? Any ideas???

 

[Tarheelpilot]

Nope

 

[Let'sgoflying!]

You're just lucky, that's all.

 

[sourdough44]

I'd start with spark plugs with the rpm drop. How old are the plugs? Do you lean in most phases of flight?

The vacuum is something else.

 

[SkyDog58]

Sounds like your mag sucks but your vacuum pump doesn't.

 

[Rob58]

Well put SkyDog. Turns out there was something fouling one of the plugs - I did a full power run-up and fortunately, luckily, it burned off the offending perpetrator-of-roughness and made the flight back to home base without incident. I'm always careful to lean things out, but the engine is high time so maybe some lead fouling - not sure. I'll be pulling the plugs hoping to learn more. The only factor that might be a contributor to this dual failure mode was the extremely hot weather - about 100F. Some coincidences just have no explanation I guess.

 

[JOhnH]

Has anyone been up under the panel lately? As often as not, when anyone goes behind my panel, when they finish I find some unrelated problem due to hoses bumped loose or pinched, or wires knocked loose or something.

 

[Rob58]

Good point - I will add this to the discussion with my A&P on Monday.

 

[Harold Rutila]

On run-up today found two serious problems: big 250 rpm right mag drop (very rough running) and no vacuum. Lycoming O-360. I don't believe in this kind of coincidence so I am trying to figure out if there is any way these problems could be related? Any ideas???

How old is the vacuum pump?

 

[Stewartb]

Start simple fir vacuum issues. Platic fittings on the back of instruments crack. Start with that.

The mag drop would make me lean aggressively and run it up hard on the ramp to clear it up.