Onan generator starting issues

[SeaNile]

Odd thing going on the past few times I've used the Onan diesel generator. Runs perfectly, puts out power, generally no issues except when starting. Not really having issues starting, but rather the starter doesn't seem to stay engaged long enough to get it to start. I have to let go of the start button or a second and then push it again to start. Sometimes it takes 2-3 pushes and other times 20. Battery does not sound weak and once it engages for more than a second or two the generator starts right up.

Nothing sounds abnormal, starter sounds good and after so many tries it does engage for long enough that the generator starts right up. All parameters are normal, no smoke, etc.

Thoughts? Could it be the 12v starting battery? Although the starter sounds fine which to me is an indirect assessment of the battery voltage.

 

[ttmott]

Doesn't sound like a battery issue.
So it does crank but doesn't start?
But the starter tends to disengage during the cranking?
I'm a bit confused on the "press the button 20 times".....
Which model of generator? MDKBN?

The QD series generators starting sequence is fully automatic. Press and hold the start button, generator primes the fuel system and preheats for around ten seconds then cranks, starts, and disengages the starter. Then release the start button.

 

[SeaNile]

It cranks but for only 1-2 seconds. Then I have to release the button, hold it down, see the lights blink then it will try to start again. Only goes for 1-2 seconds then no more. Some times I only need to do this 2x and it starts right up and others it's a 20x.

It goes through the proper pre starting sequences like it used to. And when it cranks for about 5 seconds it starts right up.

Not sure of the exact model but the sequence you point out for the QD series is exactly what mine goes through.

 

[ttmott]

Do you have two rocker switches on the house circuit breaker panel?
If so the left switch turns on the FireBoy fire system generator relay. The lamp on that switch should light up when it is turned on. That provides control power to the generator.

The right switch is a multi-function switch. Pressing down stops the generator. Pressing and holding down and not running activates the fuel pump for priming like when you change the filter. Pressing down quickly and releasing activates any fault codes that the unit might have stored. The blinking lamp on that switch is the code if any. Then pressing up and holding does the start sequence.

So - If I understand, the generator attempts to crank and when it does, the starter sounds normal but then it just stops cranking before it will start. Sometimes it will not crank at all. Then if you repeat the start sequence enough times it will crank and start. Right?

First the lamp on the left switch - does it stay illuminated when you are attempting to get it to start? It should.

If all this is pretty much what is happening then the first suspect is the K4 relay in the generator's control box. That is a $20 Bosch relay you can acquire at NAPA. Pull the top cover off the control box and it will be in there.

 

[BlueYonder]

Does it do the same thing when you start it from the panel on the generator?