Onan diesel generator won't crank, it only clicks

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The Start / Stop / Prime Button will Blink out a Fault Code if the Generator quits running or won't start for whatever reason. The Fault Codes and what they mean are Listed in the Owners Manual.

This is how you read a Fault Code.

1. If you'll look at the Start/Stop Button when the Generator stops running, it will be blinking, there will be a pause and then it will blink the same number of blinks again. Count the Blinks. 3 Blinks indicates a Service Fault. Press Stop and it will start blinking again. What you're looking for is a two digit code. 3 Blinks was the 1st Level of the code, pressing Stop will give you the full code. Example, when you press stop, you'll see, blink, blink, blink - pause - blink, blink, blink, blink, blink, blink - pause, and the blinking repeats it's self. So what code did it blink out? Right 36.

Now, if you've been gone and when you get back and the generator has stopped running, the Start/Stop Button will not be blinking. It quits blinking after 5 min. To get the Fault Code, Press Stop 3 times within 5 seconds and the blinking will start. You just need to count the First and Second Level Blinks. Example, blink, blink, blink - pause - blink, blink, blink, blink, blink, blink - pause - and it repeats. If you hit stop again, the blinking will Stop.

The fault codes should be listed in the Owners Manual.

Dead battery. Dirty battery cable terminals. Check both ends of cables. Could even have loose connections doing this. Check all of the above. Check the external start rocker switch. They get gummy being outside in the dirt and grime and sometime do not return to proper rest position holding any other switches out of the circuit and preventing starting.

jwmII wrote:
Dead battery. Dirty battery cable terminals. Check both ends of cables. Could even have loose connections doing this. Check all of the above. Check the external start rocker switch. They get gummy being outside in the dirt and grime and sometime do not return to proper rest position holding any other switches out of the circuit and preventing starting.

Also, when you measure the voltage while starting measure it at the generator not at the battery. Dirty contacts will show up as a large voltage across the dirty contacts.

When my ONAN 4k gas generator did that, it was a loose negative cable on the house battery.

My Diesel gen does that for a few seconds before it starts.
How long did you hold the button?
I know there was at least one post and the guy was just not holding it long enough.

Does new member mean new to you rv? As suggested, if this is your first time with a diesel generator this is normal during the glow plug warm up time. It can take much longer than you would think before it cranks.The preheat time could be as much as 15 seconds. This is the time before the starter even begins to crank the engine.

Yes, the new diesel generator is new to me. I had no idea that the rocker switch had to be held down so long. It started up after holding the rocker down for 45 seconds. In the last month, it started after 5 seconds or so. Thanks for the help!

if it takes that long to start, while cranking, you may have a bad glow plug. thats the way mine worked. it wouldnt start without cranking 30 to 50 seconds, after the prime time.
sometimes when it would start, blue smoke would billow out
i dropped the generator, pulled the glow plugs and tested them. one had failed. i replaced all three and now it starts right away.
its a job to remove the gen, so replace the fan belt and the fuel filter while you are doing the repair.
i got all my parts from napa. the glow plugs are ngk plugs.
the number is on the side of the plug.