Onan Generator runs without fuel pump?!?

[Kyle Routh]

I’ve had intermittent issues with our Onan 10KW generator model MDKWB (diesel) tripping the DC control circuit breaker (the 10amp red breaker) shortly after startup.  Finally dug into it last night and this is what I discovered. 

I traced it to a high current draw on startup and by process of elimination narrowed it down to the fuel pump.  And during that process, after disconnecting the electrical leads to the fuel pump, I started the generator to monitor the current draw.  I expected it to run briefly then shut off since the fuel pump was disconnected. Unexpectedly the generator ran great and ran fine for 3+ hours.  And this morning it fired up fine and has been running great all morning.

The only thing I can figure is that the fuel level in the tank is higher than the generator injectors and must have enough elevation head to ovecome all the flow restrictions, including a Racor filter and the non-working fuel pump.  Does this sound right?  

My real question is this:  will running our generator without a working fuel pump cause any unforseen problems (short or long term) with the generator? I plan to replace the fuel pump when we get back to a marina but wanted to make sure I am not doing any damage like it is.

Thanks for any info!

Kyle

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[Michael King]

I have a 9kw Onan MDKAL. I believe our fuel pumps are only used during preheat when the control switch is held in the stop position. In the stop position the fuel pump is purging any air from the low pressure side of the fuel injection system. If you ever start your generator without first using preheat, then you would also not be priming the low pressure side which is no problem if you don’t have any air in the fuel system.

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Kyle Routh

[Kyle Routh]

Thanks for the reply.  Another response I got was that since these generators are designed for a variety of installation situations, the fuel pump is just included standard whether the particular installation needs it or not.  In my case, it appears it isn’t needed.  I’ve put about 20 more hours on it since the original post so it would seem the fuel pump is definitely not needed for my setup.  Good to know!  But that is a good point about if I hear it stumbling like it is starved for fuel.  Thanks again!

[Clark Leighs]

My guess only.

When it starts to run out of fuel shut it down  rather than let it stumble a bunch.      When it stumbles it MAY not get enough fuel to lubricate itself and do some damage.  I am referring to the injection pump.

 

Just my opinion

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Kyle Routh

[Kyle Routh]

Adding a couple of pics for clarification

Thanks in advance for any insight!

Kyle

[Author]

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