Engine Won’t Shutdown

[Dialed In]

1965 E with IO 360 A1A
 

So I went up yesterday just to dink around.  While up at 10,500 I preformed three gami lean tests and an inflight mag check. On the last lean test while at about 8 gph I noticed a stumble but did not think much about it. I continued on with the mag check and everything checked normal.  Upon landing I taxi at 1000 rpm to the hanger then went to idle cut off. The engine did not die just lost about 200 RPM and the fuel flow reduced from 2.2 gph to 1.4.  I went full rich then tried again with the same results. I then shut down with by shutting off the flow divider. 
 

After cleaning up and pushing the plane into the hanger I popped a side panel and inspected the servo which is an RSA-5. The linkage is intact, the ICO screw is where it’s always been, and the cable did not slip so it must be internal. This servo was gone through two years and about 230 hours ago and has been flawless up until now.  I was too late to contact the shop that rebuilt it, I will do that on Monday and A&P’s have to travel here so I have not called them yet. There has not been any contamination in the screens nor has there ever been water sumped. You guys have any ideas on what this could be or is it just pull it off and send it in?

[PT20J]

The idle mixture and idle speed screws are on the throttle side. The mixture control is on the other side. I would check that the mixture control goes all the way to ICO. If that is good, I'd next check that the mixture valve isn't leaking excessively. Disconnect the input to the flow divider and run the line into a container. Set throttle about half open and mixture in ICO. Turn on boost pump and run it for two minutes. Measure the amount of fuel in the container. The servos are shipped from the factory if they measure 5 cc or less per minute and the servo should be overhauled if the leakage is more than 8 cc/min.

[Dialed In]

Thanks Skip that’s exactly what I was looking for. 

[TheAv8r]

I had this exact issue in my last plane, also an E model. It turned out to be an internal part of the fuel servo was stuck open so fuel never stopped flowing. The fix was to remove the fuel servo and have it overhauled. 

[carusoam]

Turned off the fuel selector valve?

The ignition switch can also work…

Did you get any other leaning weirdness?

Let’s invite @M20Doc to the conversation… (idle cut off, M20E)

 

Best regards,

-a-

[Guest]

The plunger in the flow divider is meant to lose off the fuel supply to the lines and injectors as the fuel pressure drops when you pull the mixture to ICO. Sometimes the plunger sticks.  Removing the top will allow it to be checked.

[Mooney in Oz]

33 minutes ago, M20Doc said:

The plunger in the flow divider is meant to lose off the fuel supply to the lines and injectors as the fuel pressure drops when you pull the mixture to ICO. Sometimes the plunger sticks.  Removing the top will allow it to be checked.

G'day Clarence.

The same happens to me only on very hot summer days sporadically when I attempt to shut down after landing. Is this likely to be the same cause?

IO360A3B6D

[Guest]

11 hours ago, Mooney in Oz said:

G'day Clarence.

The same happens to me only on very hot summer days sporadically when I attempt to shut down after landing. Is this likely to be the same cause?

IO360A3B6D

It’s certainly a starting point, and cheaper than sending the injection servo away.  I know nothing about Australian maintenance rules if your maintainer is allowed to open the divider to check.

[PT20J]

12 hours ago, M20Doc said:

The plunger in the flow divider is meant to lose off the fuel supply to the lines and injectors as the fuel pressure drops when you pull the mixture to ICO. Sometimes the plunger sticks.  Removing the top will allow it to be checked.

Good idea. Also, the flow divider can be field repaired-- it doesn't require sending it in for overhaul.

Skip