Generator Fuel Issue

I have a Northern Lights N673 6 kw generator on my 37' Tollycraft. On the last day of our last boat trip, the generator wouldn't start. I'm not very mechanically skilled, so I had a mechanic look at it, who told me I needed a new mechanical lift pump. I changed out the lift pump ($180) and bled the fuel lines (it has a little mechanical bleed pump lever on the lift pump), and it started, ran for a minute or so, and quit. Thinking there was still some air in the lines I tried to bleed it again, and couldn't get any fuel out of the bleeder with about a thousand pumps, and I could only get it to start and run for a few seconds.

The generator feeds off my port fuel tank, and I realized on our last trip I had run that tank down lower than I have ever had it since we've owned the boat. I probably still had close to a quarter tank -- the main engines would still run off the tank just fine -- but I wondered if maybe it was an issue with the fuel pickup for the generator. It has a separate fuel line and a separate Racor from the mains. So I filled the fuel tank to the top, bled it again, and now it runs just fine.

Has anybody heard of anything like this? Could I just have a fuel pickup for the generator that doesn't go all the way to the bottom of the tank, so it runs out of fuel before the tank is empty? What do I do about this, other than not run that tank down so low?

You had to shut off the fuel supply to change the lift pump. Did you remember to turn the fuel supply back on?

tiltrider1 said:

You had to shut off the fuel supply to change the lift pump. Did you remember to turn the fuel supply back on?

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Yes, I double and triple checked that.

Sometimes the genset pickup is deliberately higher so that the genset doesn’t run the tank dry.

Comodave said:

Sometimes the genset pickup is deliberately higher so that the genset doesn’t run the tank dry.

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I'll bet that's the answer. Thanks.

Easy way to find out is to fill the tank a bit and see if it works. May take a couple of tries to find out for sure to get the fuel level up to the pickup. But you will get really good at bleeding the genset.

I have this same issue with my Westerbeek generator. It has a small electric fuel pump but will not draw enough fuel when the tanks are low. I change to a different tank with a higher fuel level and it works fine. I also had this issue this past spring with the main engines when they quit while running on low fuel tanks. Switched to other tanks and ran fine. These engines have mechanical fuel pumps. So I am thinking everything is much happier when there is a little gravity helping the fuel get to the pumps. In both cases the fuel level in the tanks was lower than the fuel pumps on the engines.

I guess I am lucky that the bottoms of my two 350-gallon fuel tanks are higher than my primary filters. My primaries supply fuel to both my propulsion and generator engines. I would never let the fuel get that low but I imagine all engines would keep running right down to the sump level of the tanks. My supply lines draw from the bottom one inch above the sump drain valves, no dip tube supply. By the way, I occasionally test-draw fuel from the sump valve. I have only ever seen a few visible flecks of junk and never yet any water. The boat is 38 years old. Maintenance records show a "tank cleaning", whatever that involved, about 20 years ago.

You can T the generator fuel line with the engine fuel line with a shut off for when you need the genny on a low tank. That way you have control of how low to run the tank.

mike66 said:

You can T the generator fuel line with the engine fuel line with a shut off for when you need the genny on a low tank. That way you have control of how low to run the tank.

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In fact I do have it teed off.

Sorry, my reply was to OP. I also have a setup with fuel coming from bottom of both tanks, T'd on the starboard side to a separate Racor for the generator.

Comodave said:

Sometimes the genset pickup is deliberately higher so that the genset doesn’t run the tank dry.

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In the RV world, ALL are set up that way, so you can always run the main engine to get to a fuel stop.

I had a similar issue during a purchases of a Boat 15 years ago. During the Sea trial, the Genny was pulling fuel from the Starboard tank while the Engine (single Eng.) was setup to pull fuel from the port tank and return to same tank that day. The surveyor had a hard time keeping the Genny running during the Sea Trial however, everything was good onece we got back to the marina and added fuel to Starboard tank.
good luck,