4.3L Mercruiser won't shut off

[obrienp]

I have a 2007 4.3L Mercruiser. The engine starts fine and runs great, even under load but when I turn off the ignition key, nothing happens. The engine continues to run without missing a beat. It's not dieseling, it just keeps running. I changed out the ignition switch but it still won't shut off. the only way I can stop it is to trip the master circuit breaker. Then, when I reset the breaker, the fuel pump runs constantly even with the ignition switch turned off and the key removed. Any ideas what is causing this?

 

[alldodge]

My guess is you have a TKS carb and the diode has shorted out.
Look at this bulletin and note the diode test. If it is the diode, when you pull the diode it will stop the motor

 

[bruceb58]

If it isn't what AllDodge said, have you done any alternator work lately?

 

[obrienp]

I think you nailed it with the TKS SVC Bulletin. The Diode has current in both directions indicating an internal short. I'll swap it out and let you know how it turns out.

 

[obrienp]

You were spot-on AllDodge, it was the diode. After changing it out the motor runs great and turns of when its hot or cold. Thanks for the advice.

 

[TimTJR]

I am having the same issue with mine but I am unable to open your attachment allDodge. Can you send it again please ?

 

[Bt Doctur]

The link is there and working in post 2