Northern Lights 5Kw bogging down

[TJM]

What would cause my NL genny to bog down and sometimes stall out after running. The failure mode is never a hard shut down, it bogs down and sometimes revs up again normally.
This just started in the last 50 hrs of running. I have 1900 hrs on it.
Oil and filter freshly changed, Fuel filter changed and I am currently running now without the Racor filter thinking it was fuel restriction. New impeller installed thinking it was water flow auto shut off. Exhaust elbow is the original cast iron but it seems to be in good shape. I inspected it last week and it appeared clean. A new SS is months away from being delivered. Engine block runs at 185° F with an IR gun.
I am gonna check fuel lines tonight, any other suggestions ?

 

[Ken E.]

I have the same genset. Fuel delivery has to be suspect, not only clogged filters but air getting into the lines between the tank and gen. I had this happen and it's hard find air leaks...best way to start is to run a line from a jug of fuel to it directly to see if that cures your problem. I also had an errant high temp shutdown sensor. The gen would run 5 minutes and then quit.

 

[Retriever]

Any chance you're overloading the genset? The first thing I would check is the load on the genset when it bogs down. If it's less than it should be, I'd start by making sure fuel filters are clear and the air filter is not disintegrated or blocked by sound enclosure foam.

 

[ksanders]

It's not one of the safety shutdowns.

If any of those activate even for a second, the Run relay drops out and the engine stops.

I'll second retrievers suggestion to check your loads when it happens first.

 

[TJM]

Sometimes when it bogs down and might stall just the battery charger is on. We thought about the loads being too high and turned off the high load item like the water heater etc..... It still bogged down. I like the fuel cause that Ken E stated.
Ksanders, I wondered if they would shut down hard as you say, thanks for confirming.
Wet exhaust temp is not hot either, maybe 100° F ?

 

[Larry M]

Are you sure the exhaust elbow is good. When you inspected it did you remove it? Our NL 5kW was doing the same thing. I ended up pulling the generator out of the boat thinking it might be the generator side and it was too cramped to work on in place. When I finally pulled the elbow, it was restricted on the flange end and down to less than 1”.

 

[twistedtree]

Are you sure the exhaust elbow is good. When you inspected it did you remove it? Our NL 5kW was doing the same thing. I ended up pulling the generator out of the boat thinking it might be the generator side and it was too cramped to work on in place. When I finally pulled the elbow, it was restricted on the flange end and down to less than 1”.

Agreed with above. Also 100F is on the warm side. It should be more or less sea temp. You probably need to remove the elbow to inspect and clean.

 

[Bmarler]

100f isn’t hot for a wet exhaust. Anything under 150f would be ok. Wet exhaust alarms by borel are set to come on at 165 I think.

 

[Comodave]

How old are the fuel lines? They sometimes collapse inside and block fuel flow.

 

[jespchee]

I just had the same issue with my NL 5 KW generator. , spent 3 months in the Bahamas trying to solve it. Finally came to the conclusion it was the "lift" pump. i.e. fuel pump. Bought one on line for 55 (a knock off) as only one quickly available. Installed it runs better than ever. I now realize it was giving me minor problems prior for a long time. They also have a $30 rebuild kit for it. Not much to change it out. Worth a try and then like I plan to do, rebuild the NL pump and keep the knock off as a spare.