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Old 05-07-2016, 05:39   #16
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Re: Change secondary fuel filters if primary is 2 microns?

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Originally Posted by Compass790 View Post
Thats interesting re Duramax filter micron rating. I was under the impression the 2 micron filters came about because of the high pressures in common rail injection systems. But whats the drawback in filtering to 2 microns? apart from possible waste of $$ Thanks for yr input onewadd.BTW I've cut open a couple of very old fuel filters ( over 10 years sitting) with no visible signs of disintegration but not a big enough sample to be sure that it doesnt happen but I certainly arent going to chuck mine out after 2 years
No doubt there are applications that require 2 micron but the Duramax filter is 7 micron. Also, i'm not referring to shelf life, this is about filters in use. As long as they are sealed (remember, they are also designed to stop moisture) and stored protected the shelf like should be a non issue.
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Old 05-07-2016, 05:51   #17
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Re: Change secondary fuel filters if primary is 2 microns?

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No doubt there are applications that require 2 micron but the Duramax filter is 7 micron. Also, i'm not referring to shelf life, this is about filters in use. As long as they are sealed (remember, they are also designed to stop moisture) and stored protected the shelf like should be a non issue.
Sealing for storage is a good point that I bet many dont think about, esp in the Tropics. I vaccum bag my spare filters.
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Old 05-07-2016, 06:06   #18
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Change secondary fuel filters if primary is 2 microns?

I use 2 micron filters. My reasoning is that I've got a 500fg filter housing with a 60gph flow rating on an engine that moves maybe 5gph while burning 1/3 GPh. I have no reason not to have extremely clean fuel!

I do change the secondary typically every other year.

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Old 05-07-2016, 06:32   #19
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Re: Change secondary fuel filters if primary is 2 microns?

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Hmmmm have you all stuffed the words Primary and Secondary?

I think the Primary filter is the one on the engine. The Racor is the Secondary even though its in the first position, before the Primary.

Is this correct?

No.

The primary is the first filter the fuel encounters, often off engine, often combined as a fuel/water separator, and Racors are common in this application. (Ours are 30 micron, per Cummins' specs.)

The secondary comes next, often a spin-on, usually on engine. (Ours are 10 mi-cron, also per Cummins' specs.)

For OP: What density does your engine manufacturer recommend? More density isn't always better, as for example if a too-dense filter element collapses, sets up a vacuum, reduces fuel flow so that the cooling process suffers, injectors go south from there... etc etc etc.

-Chris
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Old 05-07-2016, 06:53   #20
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Re: Change secondary fuel filters if primary is 2 microns?

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In regard to usable life of diesel fuel filters, many manufactures recommend 500 hrs or two years. My training at GM was the same until, with the advance of electronics, filter life was calculated by the Engine Control Module. Now based on many factors it could be longer or shorter.
The most important part for ALL diesel engines is that fuel not only runs the engine but is the cooling and lubricating element for the high pressure pump. While restricted fuel flow will eventually shut down your engine, there can easily be excessive wear or even damage in the high pressure pump before there is enough restriction for shutdown.
While we debate the use of a 2 micron filter (I'm guessing some believe that is to protect the system better) the engineers that designed the system are saying that 10 micron is all that is needed before entering the high pressure system.
You can find on the Racor/Parker web site (I found it during my research, you can too) that they recommend no more than 10 micron for a primary filter and in higher flow engines or smaller filters using 30 micron. Their reasoning is the 2 micron is overkill and will begin to restrict flow much sooner. And of course you should have the 10 micron secondary right before the high pressure system.
A diesel lives on fuel flow and the smaller the filtered particle stopped by a filter the faster it is filled up and restriction begins (this cannot be seen by cutting one open). If you have ever had to replace a high pressure pump you know how expensive it can be.
I believe in delivering as much fuel as easily as possible to this very important and expensive part of my diesel and that the designers should know it best. Two aspirin are good when you have a headache, but half the bottle???

Ok I do go along with your reasoning about restricting sooner & yes our injection pump ( Bosch PFR) only runs about 2300psi injection pressure so no need for a 2 micron in anyones book. Got given some 3 micron filters so was trying to find out any reason I shouldnt use them. ( one is currently in use) 1st filter to see the diesel is a 25 micron & the 3 micron is after the lift pump.
Vaccuum gauge will decide the life of the 25 micron filter for me. Only use 1 and 1/2 litres per hour so it could be a long time. Bit suspicious of manufacturers time limits for filters ( gotta keep churning them out) but because I can strip & clean my injection pump as it's a simple single cylinder one it's low risk.
Interesting though if you look at bearing design according to what I've read its greater than 7 microns for the particle size that produce wear ( say in a crankshaft bearing). 7 microns is the thickness of the oil film apparently & the wear particle need to be bigger than that to protrude thru the oil film. Cant see how the plunger & barrel in the injection pump would be much different mechanically speaking but what do I know? Just thinking aloud.
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Old 05-07-2016, 11:27   #21
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Re: Change secondary fuel filters if primary is 2 microns?

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Originally Posted by ranger42c View Post
For OP: What density does your engine manufacturer recommend? More density isn't always better, as for example if a too-dense filter element collapses, sets up a vacuum, reduces fuel flow so that the cooling process suffers, injectors go south from there... etc etc etc.

-Chris
Hi,
I don't know what they recommend. I have a Perkins M130C. I'll dig through the manuals.

I don't think the 2 micron primary restricts flow. The primary's have electric fuel pumps, which fill a small day tank that the engine then pulls from to run through the secondary.

About cooling. The engine doesn't have a fuel return to the tank. The return is routed back into the secondary. I'm guessing this is bad for cooling, but I hesitate to change anything since the engine has ~5k hours and has the smoothest running and cleanest exhaust of any engine I've ever had. I'm trying to be good to it and keep it happily rumbling along forever.
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Old 05-07-2016, 12:08   #22
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Re: Change secondary fuel filters if primary is 2 microns?

Thank you guys! I've learned so much today.
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Old 05-07-2016, 12:10   #23
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Re: Change secondary fuel filters if primary is 2 microns?

[QUOTE=Compass790;2159582]Thats interesting re Duramax filter micron rating. I was under the impression the 2 micron filters came about because of the high pressures in common rail injection systems. But whats the drawback in filtering to 2 microns? apart from possible waste of $$ Thanks for yr input onewadd.BTW I've cut open a couple of very old fuel filters ( over 10 years sitting) with no visible signs of disintegration but not a big enough sample to be sure that it doesnt happen but I certainly arent going to chuck mine out after 2 years[/QUOTE]

The drawback is quite possibly that you will negatively impact the operation of your engine.

The primary filter, the Racor typically, is upstream of the fuel pump, i.e., on the suction side of the pump. As in any fluid pumping situations, restrictions in the suction side of the pump has more of an impact on pump performance than restrictions on the discharge side. The very real possibility is that you will inadverdently reduce fuel flow, impacting the performance of the engine, including the lubricating qualities of the fuel.

'Over filtering' is not better. Yanmar spec's a 30 micron primary filter, in conjunction with a 10 micron engine mounted secondary filter, for example, in most of their non fuel-rail engines. The east coast U.S. Yanmar distributor, Mack Boring, is quite adamant about this matter.

If you want to maintain your engines more frequently than the manufacturers recommend, change the engine oil more frequently. If in doubt, follow the recommendations of the manufacturer.
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