My 912UL will no longer shut down when I switch it off.  I initially suspected dieseling after having the engine drinking avgas for 18 hours.   But the engine runs strong and continuously after it is switched off when hot.  Mag checks see almost no drop or difference between left and right. I kill the engine by shutting off the fuel. I have an ACS 510-2 keyed ignition switch. Having traced the wiring from the ignition switch through the firewall I found no defects. If I shut the engine off after a couple of minutes, like before the oil warms up, it stutters to a stop.  But at 120F+ it runs after I turnoff the key switch.  Before my long XC the engine always shut down reliably.

I have referred to the schematics in the HMM part 74. I opened up the A and B six pin connectors and identified the grounds. I tested for continuity by connecting my VOM between the male pin on the connector (i.e. routed to the panel) and the negative terminal of the battery. I did this with power off and power on.


In theory:                                   Continuity  (Y=continuity, N= open)

Key Switch Position             Ground A                   Ground B

Off                                        Y                               Y

L/R                                     Y/N                             Y/N        one of A or B will show continuity; the other open

Both                                    N                                N


In reality:

Off                                     Y                                  Y      as expected both A and B grounded

L/R                                    Y                                   Y      in both L/R positions BOTH A and B are grounded

Both                                  Y                                   Y      makes no sense--if these are grounded the engine shouldn't run.  At all.




Am I doing something wrong here?  None of this makes sense.  



You do not have permissions to reply to this topic.