Rough Idle after Shutdown

[Drippy]

Guys,

I have a little over 200hrs on my IO540 and for the first time on shut down yesterday it continued to idle (very roughly) after I pulled the mixture to idle cut off. I let it go for a 10-20 seconds verifying the mixture was full back and ended up killing it with the ignition switch.

I have a light speed II ignition with back-up mech mag.

The only thing different from every other day was it was warm 85F+ but I have flown on other days like that with no issue.

I was thinking my mixture setting on the throttle may need a little adjusting but figured I should ask.

Thanks

[woxofswa]

Check the ground on the mag, but be careful with the prop because if the ground wire has broken, the mag is hot (active).

[cajunwings]

If you have the Bendix fuel servo the ?fuel cutoff valve? part is not doing its job. It?s just 2 steel plates that slide against each other and sometimes they wear a little and won?t stop all the fuel flow. They can be removed and polished to restore function.

Don Broussard
RV9 Rebuild in Progress
57 Pacer

[airguy]

Originally Posted by cajunwings

If you have the Bendix fuel servo the ?fuel cutoff valve? part is not doing its job. It?s just 2 steel plates that slide against each other and sometimes they wear a little and won?t stop all the fuel flow. They can be removed and polished to restore function.

Don Broussard
RV9 Rebuild in Progress
57 Pacer

That, or the fuel in the line between the servo and spider is hot enough to boil, and that is pushing the vapor/liquid mix through the spider and giving just enough lean fuel mix to keep kicking for several seconds. 85F and 100LL fuel, this is not real likely, but it's possible.

[Drippy]

I have the Bendix throttle - not sure about cracking it open though I had it rebuilt about 2 years ago when I did the engine overhaul.

Are they easy to get at?

[lr172]

Originally Posted by cajunwings

If you have the Bendix fuel servo the ?fuel cutoff valve? part is not doing its job. It?s just 2 steel plates that slide against each other and sometimes they wear a little and won?t stop all the fuel flow. They can be removed and polished to restore function.

Don Broussard
RV9 Rebuild in Progress
57 Pacer

I would also make sure your cable linkage has drifted or moved, preventing you from fully retracting the mixture arm on the servo.

Larry

[F1R]

Originally Posted by lr172

I would also make sure your cable linkage has drifted or moved, preventing you from fully retracting the mixture arm on the servo.

Larry

Most probable and the easiest to check.
With your mix lever in the cockpit at cut off, have a close look at the stop and mixture arm on the bendix servo body.

[Drippy]

Guys,

Great advice from all I will check the linkage first.

[mahlon_r]

Check rigging to make sure mixture cable is hitting the ICO stop.
If good
Disconnect hose to flow divider
Put boost pump on with mixture in Ico.
No more than drip every few seconds allowed. If any flow get servo fixed or lap mixture plates yourself.( if you are comfortable with that)
If no flow
Get flow divider serviced or take apart and clean again if you are comfortable doing that.
Good Luck,
Mahlon

[sdflier]

Run your RPM higher at shutoff will actually help avoid run-on