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Old 30-04-2014, 21:58   #1
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DIY Diesel Polishing

I'm building a small day-tank and a diesel polishing system for my Nonsuch 30 ( A Kiwi Nonsuch 30 Ultra: Fuel system ) and I have a minor problem.



Because this project (like everything) is being done on a shoe-string budget, I ended up with a filter/seperator and a pump that I may not have chosen otherwise, but I want to make them work.

I have a CAV-type filter with 7 micron element rated to 10-15gph, and a 12v lift pump rated to 30gph. The filter is on the suction side of the pump, but will this difference in potential flow rate cause problems? Will the pump strain and fail early...or does it care? I'm really looking for a mechanic to weigh-in here.

The lines to the filter and pump are 3/8", the return line is 1/4" (out of necessity)

John
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Old 30-04-2014, 23:24   #2
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Re: DIY Diesel Polishing

You should do whatever it takes to re-plumb it the other way.
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Old 30-04-2014, 23:28   #3
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Re: DIY Diesel Polishing

I'm not a mechanic, but I think you will be fine. The only problem I see is that you have a component produced by that whose name shall not be said out loud. I suspect that the first time you have to change that filter will be the time you return to eBay looking for a good deal on a different one - it was for me!

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Old 01-05-2014, 02:02   #4
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Re: DIY Diesel Polishing

If your pump is the electric type with pressure regulator, then you would want to put the filter on the outlet side. If the filter starts to plug then the pump will slow or stop when the filter plugs.
Also it's good to have a bowl filter before the pump to catch the large chucks before they get to the pump, depending on how dirty the tank is.
If the filter were on the inlet side the pump would keep running even with a plugged filter.

My setup is portable and I use a vane pump (raw water pump with nitrile impeller) so it doesn't matter which side the filter is on. It just bypasses the vanes when plugged and chucks will go straight thru to the filter using 12mm hose.

1/4" hose would be pushing it for a 30 gpm pump. That's 2 qt a minute. The pump would have to be at least 15 psi to achieve that. Most electric lift pumps run at about 6 psi.
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Old 01-05-2014, 02:22   #5
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Re: DIY Diesel Polishing

Hi guys, I too am making a cleaning unit. Mine is inter grated into the engine fuel system. The advantage of this is that I can If needed swap filters to use in the engine if I'm caught out with a filter problem at sea. I hope you can see the attached diagram.

Can anyone see a problem with me doing this.

The circles around the two T sections represent three way valves.
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Old 01-05-2014, 02:38   #6
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Re: DIY Diesel Polishing

Quote:
Originally Posted by Island_Moose View Post
I have a CAV-type filter with 7 micron element rated to 10-15gph, and a 12v lift pump rated to 30gph.
I'd invest another shoestring and place two filters parallel..
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Old 03-05-2014, 08:35   #7
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Re: DIY Diesel Polishing

I know that this will fall on deaf ears however....

Fuel polishing is only a mechanical way of "controlling" the microbial problem in fuel but will not eliminate it. The biofilm will remain and leaves the tank prone to failure firm microbially influenced corrosion. I am not suggesting that mechanical polishing is a waste but it won't "fix" the problem.

Fuel Right additive is designed to scrub the biofilm away and dissolve the binding agents that hold it all together. It will also leave behind a microscopic corrosion coating protecting steel tanks, lines, pumps from corrosion. Fuel Right will also prevent the biofilm from forming again. Together with your polishing system, you will have the cleanest fuel in the marina.

I have used it to remove the crap from my 30 year old tank and it works exceptionally well. I have a racor FG500 and it dumped all this crap into my racor which I subsequently cleaned out ...twice..before I was in the "clear"

My filters now last longer and my engine runs smoother and is easier to start as a result of the improved fuel quality.
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Old 03-05-2014, 08:59   #8
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Re: DIY Diesel Polishing

Don't neglect the simple act of cleaning out your tanks from time to time. Mine have generous cleanout/inspection ports that allow me to periodically empty and swab out the interior of the tank with paper towels. Plus, having a parallel filter system, a fuel vacuum gauge to measure the state of clogging in the active filter, and a terror of losing my my fuel supply while entering a potentially dangerous inlet at a bad time.
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Old 03-05-2014, 09:10   #9
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Re: DIY Diesel Polishing

There has been so much written about fuel polishing on this forum that I hesitate to answer. However, here is a summary as I see it:

If the filter is made to be placed before the pump it should be placed before the pump.

It is always best to keep your fuel polishing system separate from the engine fuel system.

Size your components so they are compatible.

Ensure the bottom of both pickup and outlet tubes are close to the bottom of the tank.

Size your system so that the flow causes enough agitation to keep stuff from adhering to the bottom and sides of the tank.

And, probably the most critical item of all, clean your tank completely before installing a fuel polisher and at regular scheduled maintenance intervals thereafter.
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Old 03-05-2014, 10:26   #10
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Re: DIY Diesel Polishing

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Originally Posted by DeepFrz View Post

If the filter is made to be placed before the pump it should be placed before the pump.

.
Most fuel filters for marine use are designed to be installed on the suction side of the pumps, so if it leaks it doesn't dump fuel inside the vessel. The last thing you want is a leaking filter spraying/squirting fuel all over. Sucking air will only shut a diesel down.

The direction of flow is important too, whether it be coalescing or particulate. The elements have a designed fiber and flow direction. A diesel filter will be coalescing.
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Old 03-05-2014, 10:34   #11
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Re: DIY Diesel Polishing

Pumps like to push. Put the filter after the pump.
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Old 03-05-2014, 10:57   #12
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Re: DIY Diesel Polishing

Quote:
Originally Posted by delmarrey View Post
Most fuel filters for marine use are designed to be installed on the suction side of the pumps, so if it leaks it doesn't dump fuel inside the vessel. The last thing you want is a leaking filter spraying/squirting fuel all over. Sucking air will only shut a diesel down.

The direction of flow is important too, whether it be coalescing or particulate. The elements have a designed fiber and flow direction. A diesel filter will be coalescing.
Given that every diesel engine I have ever looked at had a filter downstream of the lift pump, I would not say that "most" fuel filters are on the suction side.
As for leaks, it is much easier to find fuel leak than an air leak.
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Old 03-05-2014, 11:02   #13
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Re: DIY Diesel Polishing

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Given that every diesel engine I have ever looked at had a filter downstream of the lift pump, I would not say that "most" fuel filters are on the suction side.
As for leaks, it is much easier to find fuel leak than an air leak.
Don't you mean upstream?

You are talking about the screw on canister types which usually go between the pump and the HP pump. Those are particulate (secondary), not what you would use to polish the water from fuel.


And how would you filter fuel between the tank and motor?
Sucking junk up thru the lift pump?

The OPs picture shows a primary type filter.
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Old 03-05-2014, 12:08   #14
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Re: DIY Diesel Polishing

Quote:
If the filter is made to be placed before the pump it should be placed before the pump.
Sorry, this sentence is poorly worded. I agree exactly with delmarrey. The filter should be between the tank and the pump. Primary diesel filters are meant to be on the low pressure side of the pump.
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Old 03-05-2014, 12:29   #15
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Re: DIY Diesel Polishing

They have been using "lift" pumps forever. From windmills to jets. Seems like this might be another example of why boats are so undependable. I would much rather have a fuel leak than an air leak. You can find a fuel leak right away where as an air leak might plague you for years.
As there is not really any pressure in a polishing system, having a filter with a coalescing system built in does not mean it should under vacuum.
I don't think a polishing system is meant to pump out 2' of crap from the bottom. So clogging up a boost pump is not going to be a big deal.
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