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Old 15-10-2016, 13:20   #1
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Fuel feed for engine and generator

I am revising my fuel system to accomodate an additional tank and would like to deliver fuel to both the engine and generator from a single filter. The plan is to put a manifold between the filter and the engine/generator. Do I need cutoff valves on both lines from the manifold to the engine and generator? Why or why not?
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Old 15-10-2016, 16:21   #2
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Re: Fuel feed for engine and generator

Generally each engine/generator has it's own filter and often their own tank pickups. Manifolds are usually on the pickup side of the filters and of course also in the return lines.
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Old 15-10-2016, 17:33   #3
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Re: Fuel feed for engine and generator

The filter and hoses will be sized to accomodate the combined fuel flow of the engine and generator so that shouldn't be a problem although I think they will rarely be run at the same time. I don't think I need cutoff valves but I can certainly put them in if anyone can make a good case for them.
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Old 15-10-2016, 19:28   #4
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Re: Fuel feed for engine and generator

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Originally Posted by TxCoastSailor View Post
The filter and hoses will be sized to accomodate the combined fuel flow of the engine and generator so that shouldn't be a problem although I think they will rarely be run at the same time. I don't think I need cutoff valves but I can certainly put them in if anyone can make a good case for them.
Cutoff stops fuel running back to the tank or overflowing the filter housing (depending if tank is higher or lower than filter). It also gives you a positive shutoff in the event of a runaway engine.
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Old 15-10-2016, 23:46   #5
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Re: Fuel feed for engine and generator

1. Being able to service fuel systems without introducing air to both.
2. Ability to run Gen set for lights, power tools, etc if Main engine fuel system down.
3. Independent shut down ability as mentioned by Boatbod.
4. Have never seen a TRUE commercial Vessel with a common post Filter Generator- Main engine fuel feed, survey authority would withdraw certification voiding insurance.
5. Bad engineering Practice.
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Old 17-10-2016, 02:06   #6
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Re: Fuel feed for engine and generator

I just went through the same exersise this year: made a common pick up of fuel and cooling water for Panda genset from Yanmar and, common exhaust. It was reccomendation of local electrician adn, more easy to arrange. Finally, Panda was not working properly. Starting the motor empty the fuel line for genny. So, I paid for a separate fuel and water pickup (with cutoff valves) and separate exhaust. Now it works
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Old 17-10-2016, 02:25   #7
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Re: Fuel feed for engine and generator

Separate fuel lines
Separate filters
Separate cooling intakes
Common wet exhaust ok

Genny needs own electric pump, if more afar astern
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Old 17-10-2016, 07:45   #8
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Re: Fuel feed for engine and generator

Common exhaust systems, whether wet exhaust or dry are never good practice.

When an engine stops running, its very probable that a cylinder will stop in the "valve overlap" position, which means that both the inlet and exhaust valve on a given cylinder will be open at the same time. Exhaust back pressure from the running engine will force gases up the exhaust system of the stationary engine in the reverse direction, forcing exhaust into the open valve cylinder, and even pushing back thru the air filter and into the engine room. This exhaust gas contains moisture, acids, carbon, etc. and it can cause rust and other issues in the stationary engine. A real bad idea......

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Old 17-10-2016, 07:53   #9
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Re: Fuel feed for engine and generator

Having thought about it I agree that having the cutoff valves will be a big plus if I have to service the fuel system in either the engine or the generator. I think I will also put in check valves so the fuel can't back flow even if the cutoff is open.
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Old 17-10-2016, 07:58   #10
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Re: Fuel feed for engine and generator

I T the fuel off of my main Racors for both the engine and the generator without any issue.
Both the main engine and the generator have their own separate secondary filtration.
I also T'd in the generator return fuel to the main engine return fuel too, without any issue.

I have also run the main engine until the primary filter clogged to the point to where the engine sagged in RPM and shut down without it sucking fuel backwards from the generator. I learned then that the main engine with it's mechanical fuel pump will pull a higher vacuum that the generator with it's electric pump as the day before the generator started sagging in RPM and acting fuel starved.

I have no cut off valves and no check valves, and see no reason for either, especially check valves, I have seen them cause more problems than I can count.
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Old 17-10-2016, 08:32   #11
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Re: Fuel feed for engine and generator

My engine and generator run off one Racor filter, then each has it's own separate filter, no check valves. Not one problem ever from this setup with 1279 hours on Yanmar 3GM30F, 3138 hours on Northern Lights 5 KW generator. I run the generator full time when off the dock and motor cruise a lot with both engines running with no issues. When going up and down Tenn-Tom to Mobile with mast down, all is motoring with gen set running. All these hours I put on both engines from new in last 14 seasons.
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Old 17-10-2016, 08:54   #12
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Re: Fuel feed for engine and generator

To answer your question.
Put valves at drive engine and genset engine. When changing engine fuel filters, air will go where you do not want. If you have two valves, only the engine being serviced will need bleeding. Without valves, the two engines will share the air, possibly at an inopportune time, a bit later. You may also introduce air when changing this new main filter. More valves will reduce this.

Having directly answered your question, I suggest separate filters and fuel lines for the engines. Parallel flow will allow greater time between changes, in the event you end up with some dirty fuel.
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Old 17-10-2016, 15:47   #13
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Re: Fuel feed for engine and generator

There is a right way to do (separate everything) this and there are ways that may work. Your choice.
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Old 17-10-2016, 17:06   #14
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Re: Fuel feed for engine and generator

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Originally Posted by TxCoastSailor View Post
I am revising my fuel system to accomodate an additional tank and would like to deliver fuel to both the engine and generator from a single filter. The plan is to put a manifold between the filter and the engine/generator...
Bad tech. Poor place to cheap out.

Use separate supplies and returns.
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