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I've got a fuel filtration question that perhaps one of the faithful can answer. I run Dahl 200 primary filters, wilth Baldwin 957 secondaries on a pair of Cummings 504 rngines (same set up each side). I have bought my filters from a local shop in years past, and never asked what "micron" level they were, just bought them and installed them no questiopns or issues. This year, to save the trip across the state, I orderd my filters on line. For the Dahl unit, I had 3 choices of Dahl 201 replecment elements; a 2 micron, 10 micron and 30 micron. Reasoning smaller is better (capture more stuff is better?) , I picked the 2 micron. Ran the boat for about 1/2 hour after changing at the end of the sason, and then winterized everything, no issues. Recently I read an article in a magazine where they raised a concern about having too fine a primary filter, and that you need to match the primary to what the engine manufacturer recomends. They intimated that 30 micron was a better choice, than the smaller 2 micron. To me, allowing 30 micron particles through seems pretty wide open as that is just over 1 mil, and relative to an injector, I would reason pretty big. No where in any of my Cummings manuals did I see anything on what level of filtration is needed for the primary filters.

Any thoughts or experiences would be appreciated. Should I stay with the 2 micron, or go larger?

All the best - Giff

The Cummins mechanic that did my survey told me to go 30 microns on my primaries and 10 on my secondaries (spin-ons). He said that 2 microns would clog up too easily.

Gif,

Your primary filter, (the canister filter attached to the engine), is usually a 10 micron. Your secondary filter, (bulkhead mounted Racor, Dahl, etc), should be fitted with a 30 micron element. The secondary stops the big stuff from the tank, is easy to inspect, change, & usually a larger capacity than the somewhat hidden primary. The primary further polishes the fuel coming from the secondary.

Even though the canister filter fitted directly to the engine is the second filter in line of the fuel flow, it's still usually refered to by the engine manufacturers as the primary.

Br,

Patrick

Ditto 30 on the primary and 10 on the secondary. 2 is too tight for the real world.

UV

Most all engine manufacturers recommend installing a pre or primary filter before the engine.

The primary would be the racor/dahl at 30 micron and the secondary is on the engine. Most are anywhere from 10 to 2 micron depending on the type of injection system and what the manufacturer recomends.

Too small a primary not only clogges faster but also puts undo strain on the primary engine fuel pump and fuel starvation at higher rpms.. It also can create a high vacuum leading to air bubbles being pulled out of the fuel which can have an effect on engine performance.

Much has to do with fuel flow rates also. On the boat engines discussed here, 30 is standard as most flow rates won't exceed 30 to 40 gal/hr.

With burn rates averaging 10 to 20 gal/hr.

Many large yachts upwards of 1500hp each engine don't use Racor style filters as they can't handle the flow rates.
They will use various design primary filter systems made to handle 200 + gal/hr flow rates

New Volvo owners on the D series beware. Use too large a micron filter on the secondary and if something gums up the works and its called under warrantee, the first thing thats checked is the filter. Not the right size and the warrantee is not valid. They are down in the 2 micron range for the electronic pumps.

Yeah, Bruce, I was just trying to wrap my comments around what the engine manufacturers call the "primary", being the canister bolted to the block. However it's put, filter big first and little second. I'm opting for new terminology in the future: 1st stage, 2nd stage...

Guys, thanks for the feedback. Looks like I will order up some more porous filters.

Captain Pat- I am always Bass ackwards on which is primary vs secondary myself, so i looked up the proper nomenclature before I made the post. In my mind, primary would be the engine mounted filter, though that uis not the genarally accepted nomenclature as I found out.

Pat,
Yea I knew what you were trying to say but just trying to keep the tourists from being confused and I think your terminology of 1st stage and 2 stage is spot on.

Not tryin to butt in here .. maybe I can add my 2 cts.
I had raycor 500s between the tank & secondaries.. Then I added a raycor 1000 next to the tank w 30 .

30 10 & 2 on the engine..
We got fuel problems where I fuel.
Think thats to much restriction?
Wayne

Wayne - if you have a bunch of particulate matter in the fuel that's between 10 and 2 microns you will clog in time. My Cummins 6BTAs seem to eat stuff less than 10 micorns with no adverse effects and have been doing it for 20 years. I used 2 micon secondaries a few times and they clogged pretty quick so went back to the 10s. BTW, the symtoms of clogged primary (on the suction side of lift pump) and secondaries (on the presssure side) are different - suction side gives variation in rpm but pressure side gives you just a steady reduction in wot rpm.

UV

Thanks Vic: Ill watch for that.. Ive changed fuel docks for now.. Well see.
Wayne