» » » Why Won’t my Cummins Marine Diesel Shut Down?

Why Won’t my Cummins Marine Diesel Shut Down?

Have you gone to shut down your engine, turned the key “OFF” and nothing happens? The engine continues running as if nothing has happened? There are a few different issues that can cause this to happen:

#1: Alternator Backfeed to IGN

In most cases, a diode is placed within the alternator voltage circuit that prevents the alternator “field” voltage from holding the fuel shutoff solenoid in the UP position. If this diode is missing, fails, or there is a short in the wiring harness which allows voltage into the IGN circuit, the engine will not shut down when the IGN key is switch to the OFF position.

Cummins Marine B Diode Location
Cummins Marine B Diode Location

#2: Sticky Shutoff Solenoid

Does your engine show it’s age? A little bit of rust here and there over time? It’s possible that your fuel shutoff solenoid has begun to “stick” open and is not letting you shut down your engine when you want to! Time to check that it travels “as expected”…

Rust Binding Fuel Shutoff Solenoid
Rust Binding Fuel Shutoff Solenoid