Fuel Polishing system

[MWybo]

Hi Roger, Sorry to intrude on your forum but I would be interested in hearing how your fuel polishing system has fared. I am in the process of installing something similar to what you describe on your Strider site and wonder what your experience has been. Could you also provide a few details on what filters you are using, which model of Walbro pump you installed, and any changes or improvements to the system you might make after your experience.

Thanks

Mike

 

[Roger Long]

It has worked flawlessly for thousands of miles. When I change the regular filters every year, it looks like they had just been in for a couple of weeks.

The only problem I have had was early failure of the Walbro polishing pump. It is rated for fuel polishing use so that is a mystery. The replacement is still going strong after hundreds of hours more service.

My system violates several conventional wisdom points such as having a common suction for both the polishing system and the fuel system and returning fuel to the fill lines. My Yanmar does not have a return line as most diesels do. The excess injector fuel is simply returned to the engine mounted filter. A diesel with a fuel return line to the tank might have issues if piped up like mine so some careful thought should be given to the system design.

If at all possible, you should have separate suction and return for the polishing system. The polishing return should have a dip tube that discharges the fuel at the bottom of the tank to help keep stuff stirred up.

Full details of my installation can be found here:

http://www.cruisingonstrider.us/FOpolishing.htm

If I were building a new system, I would give some thought to installing a larger tank like the one described here for my heating system:

http://www.cruisingonstrider.us/10Winter.htm

This tank would then gravity supply the engine. This would be a solution for a situation where additional suction and returns could not easily be added to the main tank.

Since the boat would be dependent, beyond the capacity of the gravity tank, on a single pump for fuel, I would probably plumb in a back up pump in parallel as is sometimes done with filters.

I just checked the little vacuum breaker valve described which is the original one installed and there was no sign that fuel had ever reached it. It looked as good as the day it went in since the air bubble in the riser tube protects it.

 

[Roger Long]

Here is what the system would look like:

The output line from the "Day Tank" (it isn't really one but that's the closest common name) should be a couple pipe or hose sizes larger than the input. Do not tee the engine return line into this line but run it directly to the day tank.

The Bleeding Pump would have a push button switch. It's primary purpose is filling the filters and bleeding the engine lines.

If the polishing pump or filter should fail, the red valve can be opened and the isolation valve on the Shelco Filter closed to turn it into a typical fuel system. A SPST switch in line with the push button on the bleeding pump would turn it into an engine fuel pump. It should be a model suitable for that use. That refinement might not even be necessary if the main fuel tank is above the engine as in many boats.

A second Racor in parallel is probably overkill for this system as the Racor will never see fuel that hasn't been through the polishing filter.

This is what the vacuum break valve looks like:

A Forespar Marlon 841 Vent/Duckbill replacement kit duckbill fits a 1/4" compression fitting like it was made for it. The 1/4" copper line should be run as high above the day tank as possible to keep the maximum air bubble in the line to protect the duckbill from fuel. Another compression fitting goes on the tank top.

 

[MWybo]

Roger, Here is what I am proposing to install. By stern tank sits above the engine and fuel is gravity fed to the Racor and then to the engine (This is your Day Tank, mine holds 30 gallons). The "Bleed Pump" is an outboard motor squeeze bulb (which works great !). The fuel supply to the engine is completely isolated from the polishing system, which using the three way valves serves as a transfer system for fuel from one tank to the other, or at least that is how it is supposed to work. See any issues with this design ?

Thanks

Mike

 

[Roger Long]

See any issues with this design?

No. That's a perfectly good way to do it. You are fortunate to have the extra tank connections.

Two suggestions:

It's pretty cheap and simple to add a cross over line from the polishing system to the engine supply. That will let you keep running while you change the Racor filter (see my schematics). It isn't likely that the Racor will ever have a problem with the constantly polished fuel but, if a marina should dump a load of gunk in your tank, as can happen if you get there just before they run out, the Racor could get loaded up before the polishing system can clean it.

For the same reason, use a three way switch on the polishing pump. One position, "On", runs it even if the engine is off. This will let you clean fuel in the spring or at the dock without having to have any running through the engine. Other positions are "Auto" connected to the engine "ignition" harness, and "Off"

It's a conventional no-no to combine tank vents but I did in my two tank system both for convenience and so that a mistake in transferring fuel from one tank to the other will just send it around and around through the vent connection instead of overboard. It hasn't caused me any problems but, if I ever try to sell the boat or need a survey to upgrade my insurance, it's sure to be written up as a "problem".

I wasn't able to find any three way valves I was happy with. A pair of straight valves are fine as long as you remember that one always has to be open and one closed. A valve each side of the Racor and close to it will reduce the amount of fuel that drains when you change the filters and the amount of air you have to deal with when bleeding the system.

 

[MWybo]

Thanks Roger, I will proceed with this design and let you know of my experiences. If you do head north look me up in Shelburne.

Mike

 

[DougFir]

Roger, where did you get your Shelco filter from? Were you able to spec it out, or was it a off the shelf unit? I am thinking of going to a 9 3/4 length, and adding the gauge port in the filter outlet.

DougFir

 

[Roger Long]

Roger, where did you get your Shelco filter from?

http://www.shelco.com/

You could have Googled it faster than posting

Do go with the full length elements if you can. It's been a pain finding the half length ones, at least in the blown plastic elements. The suppliers buy the full length and cut them in half. I had to send one shipment back because someone had clearly done it with a large tooth carpenter's saw and the ends were so ragged and angled that they wouldn't seal.

Ask for John Zotter if he is still there and give him my regards.