Pearson 33 on-board diesel fuel polishing

[Michael Cyr]

All,

I hope everyone is on their own particular schedule for getting in the water!  I decided I wanted to have an on-board fuel polishing capability but I don't want to have separate filters or pumps. I've always had a 12v aux pump for filling the fuel filter and helping to bleed the fuel system. With the addition of a 3 way valve, I want to add the ability to circulate fuel from the tank thru the filter/water separator and then back to the tank. Of course, this would only be possible with the engine off (unless I can find a balance on the three way valve that will keep the engine fed and send some filtered fuel back to the tank.  Thoughts?

Mike in Maine

1970 P33-1

Yanmar 3gm30f

[Dave Cole]

I would make your fuel polishing system separate from your main fuel system.   You may need to add a fuel pickup and another filter to do that.

Regarding your plumbing diagram;  do you intend to run your aux pump whenever you run the engine?

Many/ most electric pumps will not allow fuel to be sucked through them.

I would put a strainer before the pump.  Otherwise it could jam up with grit.

Dave

10M #26

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[Jeff Griglack]

The mechanical pump on my engine failed before I bought the boat, so the PO (really the yard where he had the engine work done) installed an electric pump.  It works well now that I rewired it so it is only on when the engine key switch is on (it used to be on as long as the battery  was turned on).  The fuel pump is after the primary and secondary filters.

If I were doing what you are proposing, I would probably add a Y before the primary fuel filter and install a new filter and pump.  Then I would install another Y on the fuel return line.  This would bypass the engine and engine fuel filters, but you could use the same fuel pickup and return lines.

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| Jeff Griglack             "Jabberwocky" P-365 #269

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[Michael Cyr]

Thanks to both for you comments and suggestions!

1. This pump does not have to be on for the engine to run and suck fuel through it (it is advertised as such and I've run it that way for years). 

2. The prefilter sounds like a good addition.

3. I like the idea of a Y before the pump(s). Unfortunately I just don't have the room for another pump/filter and hence looking at implementing this diagram. Great suggestion though!

4. One drawback of this design is that I can't polish and run the engine at the same time.  I probably WANT to polish when the tank is stirred up at sea.. so that means polishing under sail. The risk is that that something will get stirred up that get's sucked up by the pump and clogs the systems, which then necessitates a cleanout at sea before being able to run the engine. Whereas with a separate system, only that separate system would be clogged.  I do always carry a spare filter, and the filter is in a readily accessible location at the front of the engine compartment, so easy to change. That mitigates the risk somewhat.

Thanks again!

Mike

[Guy Johnson]

Anytime your diesel is running it's polishing fuel, extra filtered fuel is returned to the tank by the return line. 

An external independent pump would allow polishing fuel using the full capacity of the filter system. 

Guy

Puffin 10M #6

Original Atomic 4 :>)

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To: pearso...@googlegroups.com <pearso...@googlegroups.com>
Subject: Re: [pearson ] Pearson 33 on-board diesel fuel polishing

 

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[Michael Cyr]

With an injection pump, rather than common rail fuel injection, the only fuel overflowing and returning to the tank is the small amount that didn't make it through the injector on each pulse.

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[Dave Cole]

It could be done with Y valves as well.

My fear is air leaks on the vacuum side of the pump in a diesel setup.  It seems like any air leaking into a diesel fuel system results in injector pump problems.  That can result in a dead engine at sea.

Many pumps, like the Carter traditional series of fuel pumps, will live a long life, with only a strainer on the input.  

In most cars and trucks now, the fuel pump sits in the tanks and they use a nylon strainer on the pickup.  Thats the only thing protecting the pump.  The same goes for diesel light duty trucks.  

So, just some things to think about.

Dave

10M #26

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[Michael Cyr]

Thanks Dave.  That's one reason I put the pump as the first device since any of the hose clamp connections along the way can develop air leaks, and actually have in the past. I used to have the aux pump between the filter and engine lift pump.  The preceding filter/water separator developed an air leak that was tricky to find.  By having the aux pump first, if I end up with fuel starvation from a small air leak, I can run the aux pump and push the fuel thru to the engine pump.  The only failure point in that case is the hose to the aux pump and the aux pump.  I also carry 5/16" joiners so I can quickly remove the aux pump if it develops a blockage.

Mike

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