My 16 HP Onan Engine Starts and Then Stalls

The 16-horsepower Onan diesel engine -- also known as the Cummins Onan QD MDKBM -- powers generators for boats around the globe. As reliable as the 16-horse Onan is, it occasionally stalls shortly after it starts. When that happens, the digital display or the control switch status lamp becomes your new best friend, as it tells you what old failing or fresh disaster has befallen the engine; there are three potential causes.

  1. High Engine Temperature

    • If the engine overheats and is not allowed to cool before it is restarted, it restarts, then shuts down. The Onan 16-horspower engine is cooled by a radiator-like system called a "keel cooler," a heat exchanger on the outside of the hull that uses the cool water surrounding the vessel to cool the liquid flowing through the cooling system. A leaking or broken coolant line, a damaged coolant circulating pump, damaged keel cooler, or a keel cooler that's clogged with the flora and fauna present in the water can cause the engine to overheat. If you press the "Stop" button, the digital display flashes the number "1" or the control switch status lamp flashes once.

    Low Oil Pressure

    • Low oil pressure from a failed oil pump, an internal clog or a lack of oil causes the Onan 16 to shut down. The digital display flashes the number "2" or the status lamp flashes twice to indicate the reason for the shutdown.

    Service Fault

    • Service faults are indicated by a "3" followed by a two-digit code, all on the display screen. It's a bit trickier when you only have the status lamp. After the lamp blinks three times -- and it will continue blinking until you press the "Stop" button -- the two-digit code begins to flash. The code is delivered in two chunks. It consists of a series of up to seven blinks followed by a brief pause, followed by up to nine blinks.

    Code

    • The code used by the engine to tell you why it shut down after it was started is cumbersome. Once you've recorded the code from the display screen or the flashing lamp, you'll find the the codes in Section 5 of the Cummins Onan Operator's Manual, in Table 5-1. After you've decoded the flashing lamp, push the "Stop" button twice to clear the code. You then can take the necessary steps to alleviate the problem before restarting the engine.