Generator Help

[Dulcesuenos]

Trying to figure out a very intermittent problem on a phasor 7.1, Kubota 3 cyl genset the issue has been going on about 2 years. It will sometimes sputter and stumble for a moment then pick up and run fine again. Sometimes this trips a breaker on the genset, sometime an inside breaker trips on one leg or both, sometimes no breaker trips. This happens either a few times a day or 1x in 2 weeks or anywhere in between. We have isolated the fuel tank, no difference, new filters, bled the system, checked engine fluids, and temperatures, (when it's a sensor, overheat or oil it does a hard shutdown, we've tested sensors)
Any ideas what else it could be or has anyone run into this?
Thank you in advance,

[smac999]

The only thing that should be tripping breakers is over current. Over current (problems with losds) would likly effect the gen running until the issue stops (when breaker trips). I would take a close look at which breakers are triping and those devices.

Do you get breakers pooing on shore power with all the same devices running?

[a64pilot]

When the generator drops in RPM the voltage drops, a drop in voltage means the current increases to maintain the same wattage of draw, so yes it can be pulling X amps at 120V, but when RPM drops, voltage drops, and amps go up enough to trip a breaker.

I’d suspect an air leak in the fuel system, look especially if you have any valves, like a fuel shut off valve, they can sometimes let air into the system.

I think breakers are a red herring, I wouldn’t spend my time trying to fix that, I’d solve the engine dropping in RPM.

[Dulcesuenos]

Thanks, A64, I'm pretty sure the breakers are because of the drop in rpm. We will revisit the fuel system

[transmitterdan]

Only a fridge or air conditioner will increase amps when voltage drops. Most other devices such as water heater, electric stove and the like won't do that. So if the breaker that is tripping connects to an AC motor then it is probably the stumble causing the problem. If the tripped breaker is something like a hot water heater then it may be an intermittent that is causing a sudden increase in current which in turn stumbles the engine. I would want to know what breaker(s) trip.

[a64pilot]

They said the generator breaker itself, or one leg inside, I took that to mean the main breaker at the panel.
Then there was the comment that sometimes no breaker trips, just an RPM drop from the generator.

[Fuss]

I also agree, the problem is engine based not the generator or external power users.

[Fuss]

could we have some updates?

[Dulcesuenos]

Ran several hours since and no stumble, but sometimes it goes weeks then does it again every few hours, it's incredibly intermittent

[Fuss]

check all connections from tank to engine.
what’s the fuel level at the time it happens full or low? try connecting a cheap electric pump to the fuel line to alter the dynamic from sucking to pressure fed to see if it makes a difference

[Fuss]

does it happen after generator has been running over a certain amount of time

[Dulcesuenos]

Originally Posted by Fuss

does it happen after generator has been running over a certain amount of time

It could be in the first 5 minutes, hour, after 3 hours or not after 3 hours a day 3x a week for 2 weeks. Zero consistency in it and it almost never dies, a secondary electric fuel pump makes zero difference as did bypassing the tank and lines and running it off a Jerry jug.

[a64pilot]

Be very unusual but if your sure it’s not fuel related, then it could be the governor inside of the HP fuel pump, or maybe checking the fuel stop to see if there is anything loose?
Just shots in the dark

[Jolly Roger]

I’m interested in this because I have the exact generator setup. I’ve never had this problem but it sounds to me like A64pilot is nearer the mark, with the speed governor. Mine runs at 1800 rpm and has never faulted.

[Dulcesuenos]

Thanks A64, im not convinced it isnt fuel related , i have checked the fuel cut off solenoid everything seems good and it functions properly when a sensor is activated. It may be really tough to diagnose until there is some regularity