Fuel Tank Return Line

[Bill19233]

I am going to install a dual filter/fuel pump system on my boat. I thought I researched it good enough before I fabricated it, but I've changed it a half a dozen times and I need to just install it this weekend before I change it a half a dozen more. I was planning the hose runs and now I'm wondering if I can tee the tank return hose into the existing return hose from the engine near the tank end, or if I need to install a separate tap into the tank for it? Will I cause problems with the engine fuel system putting pressure on the back side, or is it not enough to worry about with the open hose end at the tank? Am I overthinking this, does anyone have prior experience or thoughts about this, or anything else I should look at? I plan on using the fuel pump for bleeding more than polishing. Thanks.

 

[Steve Dion]

Bill:

This is what I did on my Yanmar 3JH2E. I used the existing hoses from the original Racor 110.

I had issues on space for mounting too.

http://forums.hunter.sailboatowners.com/showthread.php?p=701862&highlight=dual

 

[centerline]

Bill:

This is what I did on my Yanmar 3JH2E. I used the existing hoses from the original Racor 110.

I had issues on space for mounting too.

http://forums.hunter.sailboatowners.com/showthread.php?p=701862&highlight=dual

looking at the photo in the link, what I see is 2 filters plumbed parallel, without redundancy as the wording suggests.
I see an inline shut-off going IN to the filters, and an inline shut-off coming OUT of the filters.... when only one valve is on, the fuel will be going in but wont be able to come out (or vice versa)... and when both vales are on, the fuel will be able to pass thru BOTH filters ALL the time...
what you show here is a LARGER filtering capacity before needing to change filters, but not redundancy..

plumbed differently, you could have redundancy with two filter bases, and as you have it plumbed now, a single large capacity filter would give the same results.

also, the fuel needs to be filtered twice. you NEED a primary to catch the water and the debris, and you NEED a secondary filter to catch the small stuff that may pass thru the primary due to a faulty filter or lack of timely filter changes.
injector pumps and injectors genuinely hate debris and water in them, and it WILL, without a doubt, cause problems.....

never think a primary and secondary are called that just because of where they are located in the system, OR that a primary is good enough... because it isnt!!! it may work for awhile, but not for long.
you can use a secondary by itself, but it will need to be changed more often.
The real problem will arise if you get a faulty filter and it lets unfiltered fuel pass into the injector pump.... and faulty filters are not as rare as one might wish they were .

the filter media inside each filter is different and designed to be used together, and should be

 

[centerline]

I am going to install a dual filter/fuel pump system on my boat. I thought I researched it good enough before I fabricated it, but I've changed it a half a dozen times and I need to just install it this weekend before I change it a half a dozen more. I was planning the hose runs and now I'm wondering if I can tee the tank return hose into the existing return hose from the engine near the tank end, or if I need to install a separate tap into the tank for it? Will I cause problems with the engine fuel system putting pressure on the back side, or is it not enough to worry about with the open hose end at the tank? Am I overthinking this, does anyone have prior experience or thoughts about this, or anything else I should look at? I plan on using the fuel pump for bleeding more than polishing. Thanks.

I would say wait on the install until you see the simpler way to do it... that is COMPLICATED.....
think of how you, or someone else is going to change filters when you are in a seaway or a near panic situation and one valve gets missed.... which one got missed.. Hmmmm, let me see, I'll just get the map of the fuel system valving out and study this for a minute or two and get it right.... ok got it....
Oops... now I forgot which way to turn the valves to get the other filter online.... and which filter was that now???.... ect, ect.....


My point is, there is an easier way.....

you have one fuel line in.... and one fuel line out.... two filters side by side.
on the inlet port of the filters install a shut off on each filter.

use a "T" to plumb the in-feed line to both valves.... OK, inlet side is done!

Now, on the going away side of the filters, using a "T", plumb the out-feed line into the filters...
then install a single shut off AFTER the "T" in the single line......

OK, now, at this point the redundant filter system is installed and complete!

the single inline valve going to the secondary filter will never need to be shut off except when servicing the filters....

if you want the flow to go thru the left filter only, open the left valve and close the right side... and/or vice versa....
the flow will never pass thru a filter that has one port closed... and neither will it drain out of that filter.

upon your choosing, you can run the filters in whatever combination you want to, or shut them off in any way you desire, with only 3 valves.


now onto your Question... Im not sure about the ABYC standards, but on modern land based diesel fuel systems, the return line is plumbed back in to the line at the secondary filter base designed for this... this eliminates the tank return line....
on our systems without the special filter base, I would think it would be best to plumb it in between the tank and the lift pump... this way, there would never be an issue with airlock...

 

[Bill19233]

I do admit the set up looks complicated, but in my opinion, it is simple to switch if the filter you're running on clogs. The photo shows normal running configuration. If filter A clogs, you open the valve on filter B. No downstream and upstream 3-way valves to make sure are turned right. Just open one valve, one quarter turn valve, you don't even need to close filter A, its clogged and has no flow anyway. If filter B clogs right away, you're hosed no matter how many valves are in the system. But, I would valve the pump in to get enough fuel thru the clogged filters to get out of harms way. I have done that before with the squeeze bulb I have on the single Racor I have now. I know... all kinds of issues doing that.

I was going to put the squeeze bulb back in, that's why the valves are there for the pump, so it wouldn't always hosed in if it leaked and fill the bilge with fuel. But I found an inexpensive Coast Guard approved low pressure pump on Amazon. And the other valves are there to keep my options open for filter changing, bleeding, maintenance, I can even polish the fuel back to the tank or pull the hose and stick it in a jerry can and empty the tank for cleaning.

And it's a 3GM30F with a secondary 2 micron on the engine, or primary depending on your point of view.

 

[Bill19233]

Oops, forgot photo.