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Old 16-09-2019, 11:59   #1
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Fuel system help

Hi folks,

Got another few questions for you. Here is the situation. I have a catamaran with 2 x Yanmar 27 hp motors. They have intermittently struggled with priming issues and shut down with air in the fuel. I know air in the fuel is a monster to track down sometimes. The fuel tank is located far forward of the engines and is much higher up than they are. I pulled the fuel tank for some other related work. I noticed the fuel lines are hardened. I'm assuming air is getting in somewhere.

In the short term, I'm considering two options (I don't have time right now to replumb the fuel lines all the way).

1) I install day tanks at the engines and pump fuel from the main tank into the day tanks.

2) I just try to install a fuel pump at the main tank and hope the "pushing fuel" instead of letting the engines "suck fuel" resolves the issues.


Thoughts on best approach?


Also other related questions....

1) Which fuel pump should I use? I'm assuming something that is continuously pumping and low PSI like a walbro FRA series, but totally unsure of that. I don't know if the walbro pump will allow fuel to flow when powered off. Can someone school me in pumps?

2) How or where does one find the parts needed to make a diesel day tank? I've read other threads where people added fittings onto tanks, but I'm not sure what all work is involved here.
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Old 16-09-2019, 12:35   #2
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Re: Fuel system help

As a side note, I think the total lift from the tank until the hoses flow downhill is roughly 3-4 ft.
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Old 16-09-2019, 12:52   #3
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Re: Fuel system help

With a day tank you are sure to eliminate the problem.
With the push fuel pump you “hope” to have eliminated the problem.
I think the option to solve the problem in the short term is clear!
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Old 16-09-2019, 13:13   #4
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Re: Fuel system help

True, but a day tank is something I've never done before. How do you find one? How is it plumbed? Does it have to be vented? Do you have a tap a new fitting for the supply side to fill it or will that also work as a vent, etc?
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Old 16-09-2019, 13:25   #5
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Re: Fuel system help

(I don't have time right now to replumb the fuel lines all the way)

I have the impression that the replumbing is a more final, better and quicker solution then installing day-tanks as a stop gap solution. All the more as you have to invent the day tank setup and installation.
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Old 16-09-2019, 13:57   #6
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Re: Fuel system help

Quote:
Originally Posted by ThereAndBack View Post
True, but a day tank is something I've never done before. How do you find one? How is it plumbed? Does it have to be vented? Do you have a tap a new fitting for the supply side to fill it or will that also work as a vent, etc?
Any diesel tank will need
1. Fill tube
2. Outlet tube to feed engine
3. Return tube for unused fuel
4. Vent tube
I recently made an aux tank using a 16 gal gas tank out of an auto. Vent and outlet tubes hook up same as with gas, I fashioned the return line into the fill tube with PVC t-connector and threaded adapter (couple $ at hardware)
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Old 16-09-2019, 14:33   #7
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Re: Fuel system help

Hi - virtually any automotive diesel pump will work both pumping & when off allow fuel to be drawn through. I have 2 very cheap ones in my catamaran's engine bays (2 aft diesel tanks) and a larger one forward for the the 2 forward diesel tanks. I have attached a video if that is helpful.
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Old 16-09-2019, 20:02   #8
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Re: Fuel system help

I would have thought it was a bit easier to run some new hose from tank to engine than to install a day tank tho a day tank is a good system.
These pumps work:https://www.trademe.co.nz/motors/car...196ed31d66-001. & they don't cost much.Pick your own seller. I have used one for bleedings. I THINK they let fuel past when not running.
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Old 16-09-2019, 21:00   #9
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Re: Fuel system help

I'm with Compass. You have an air leak in your old, hardened (i.e. cracked somewhere) hoses. It's way less work to just replace those hoses than to futz with other "stopgap" measures that are more work and don't actually solve a simple problem but just give you a workaround.

Buy whatever you need of 3/8" (or whatever you have) and fish the new hoses through following the old ones. Should not take more than an hour or two.

Lastly, old fuel hoses are a hazard. Fix the problem instead of masking it.
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Old 07-10-2019, 07:41   #10
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Re: Fuel system help

I wanted to thank everyone here for their advice. A lot of times I feel good advice is given on this forum and we never know the outcome (for good or bad) of all that advice.

After some thought and consideration, I decided to just go ahead and replace the old fuel hoses. All 180 ft of them. That is 4 hoses each run roughly 45 feet through the boat, through lockers, sometimes conduit, sometimes not, behind and under and over all kinds of stuff.

I laugh now at the suggestion that "Should not take more than an hour or two.". It took 3 people (2 of which are highly skilled fast workers) a long and tiring day. So that is roughly 30 man hours. If it were only 2 people doing the job it would have been a lot longer in man hours, and 1 person... God help them.

That said, I'm still happy it is done now. Hopefully these new fuel hoses will last at least another 20 years. As for the day tank idea, I've given it up, but I'm still considering the electric boost pump.
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Old 07-10-2019, 13:45   #11
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Re: Fuel system help

Thanks for posting back the results
Now we have an accurate description of what it entailed day tanks don't sound that bad!
Na, still think it was better to replace as if they started leaking somewhere it would be a pain.
FYI one of our yanmar fuel hoses lasted 36 years but it crumbled in my hands when I finally removed & replaced it.
In the manual it says replace every 4 years, but that's clearly overkill.
No reason why you can't fit a boost pump.
BTW did the new fuel lines fix the problem?
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Old 07-10-2019, 14:49   #12
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Re: Fuel system help

I haven't gotten to the point that I can test the new fuel lines yet. Still waiting on the fuel tank to come back from the welder.

I think I'm going to fit electric boost pumps at each engine as precaution. I'm also probably just going to replace the racor filters while I'm at it. So everything in the fuel supply side will be new except the tank itself, but that will be refurbished.

Project creep. It hurts to "do it right" every time, but hey, I guess it is what must be done.
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