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I am going to start setting up my 4BT's next month. I was wondering what some others are using for fuel filters.

My engines (150HP 3.9M's) have cummins installed fuel filters that are mounted on the engine.

Should I run another fuel filter between the Tank and the engines fuel filter?


If so, then should it be a primary or secondary filter?

I dont know the difference between the two.

Yes a primary.. Should be at least a 30 Raycor 500
Wayne

Racor 500, the one on the right, is what I have. In addition the spin-ons on the engine. The Cummins mechanic told me 30 microns in the Racor, 10 microns for the spin-ons.

I am reviving this thread with a few more questions.

Since I only have one tank, Can I run 1 (one) primary filter and split off for each engine?

How many microns should the PRIMARY be? 25-30???

Can the primary be a water separator as well or they dont come like that.



I ask only because a friend of mine has given me a brand new Fram set-up part number FCS1133PLM.
It is 2 large INLINE metal filter housings that each have a different replaceable filter element, one serves as a filter down to 1 micron the other serves as the separator.
This dual setup is rated at 100 GPH.

The 4BT's only do about 7GPH each max.

I was thinking of running this off the tank and then splitting supply to each engine AFTER this filter, it would then of course go thru the Cummins spin-on's that are on the engines.

I have not done anything yet with the fuel system and am only looking to see what I can do and can not do.



Frank V

I have cummins 6bta's. I have 1 racor for each engine, 900 ma's. The filters are 10 microns, although I was told by the cummins guy I could use the 30's. You may only burn 7 gallons an hour but you have more fuel passing through for the return. Some fuel is used as coolant and lube then retuned to the tank . Hope this helps Russ

scenarioL113 wrote:I am reviving this thread with a few more questions.

Since I only have one tank, Can I run 1 (one) primary filter and split off for each engine?


Frank V

Frank- there are a lot of folks with more knowledge than I have here, but I will give you my thoughts on this matter. Most diesel problems are caused by fuel issues. One issue that does come up is your primary filter getting clogged, and having to be drained and cleaned. Now, if you only have a single primary and it clogs, then you have lost both engines. If you have individual filters, odds are one will get to the fail point before the other. Leaving you one engine in use while you are cleaning and priming that clogged filter.

I don't know if you have ever been 80 miles offshore and had both engines fail, but I can assure you it is not a good experience.

Bottom line, individual filters.

The "primary" and the "secondary" are named by where the filters are in the fuel flow from the tank to the injector pump....the primary is the first filter from the tank and the secondary is the second, and usually last. If you had three filters I guess the last one would be the "tri-ary"?? In any event the conventional set up on engines like yours is a Racor 500 are the primary with a 30 micron filter element and the secondary is the spin-on that is mounted on the engine already by Cummins. I use a 10 micron secondary but a lot of folks use a 2 micron secondary.

The Racor is a water separating filter and needs to be drained from the petcock at the bottom frequently. The idea of using one Racor "primary" for both engines is not a good one for a variety of reasons, starting with the certainty of airlocking an engine when changing filter elements.

I have Cummins 6BTA 250s and use the Racor 500s with no issues. Just be sure you mount them where you can get at them easily to not only pull the elements out the top, but also to dran the bowl into a cup rather than let the diesel go into the bilge and stink things up. Use high quality fuel hose, at least 3/8" i.d. and high quality fittings. A ball valve in the fuel line between the tank and the Racor is a must for shutting off the backflow when you change filters to keep from airlocking the engine.

UV

I have to agree about the single filter issue taking down BOTH engines and I will NOT do it.


On a side note,

I can run these dual filters separately and off separate pick-ups and install the 1 micron filter in each of them. The housings are identical and they both have a drain on the bottom of them to empty the water.

It really is not a big deal to use these particular units but since I had them I figure I may give it a shot.

Since the filter element provides 1 micron then maybe they would not be a good choice to use as primary. Is that safe to say?

One micron is way too tight for diesel...you will clog them all the time even with the cleanest of fuel, which is why most of us use 10 micron as the tightest vs. 2 micron.

Cummins exhibit very distinct symtoms of clogging filters: on the primary, which is on the suction side of the fuel lift pump, the rpm will vary; on the secondary, which is on the pressure side of the fuel lift pump, the rpm will just decrease and stay steady at WOT.

Microns are little bitty things.....I find that the 30 micron primary clogs about 5 times for every time the 10 micron secondary needs changing. Running too tight on the filters will cause you untold misery.....

UV

Vicroy wrote:If you had three filters I guess the last one would be the "tri-ary"?? I

It would be the tertiary filter, UV. Frank, UV is spot on about too tight filters being trouble. What's the old saw, even too much af a good thing is bad.

I can attest for the misery part. It was not that bad but could have been.
About 20 or 30 hours after the new install I had company down and we were boating of course. We were coming into a narrow winding channel near Duck Key and my cruising RPM had become my WOT RPM. When I cam off plane both engines quit.
After some looking around I noticed the primary filters that we installed in the Raycor 500 were 2 or 10 micron, can't remember but way to fine. The fuel still had to go thru secondary which is 2. I was later told that the red dye will not even go thru two filters that are that low(high?) in the micron scale. Slapped in some 30's and good to go.
On a side note, I have a direct fill hole in the top of the tank. With engines at idle I can see tons of fuel returning to the tank and it sounds like a waterfall. there is lots of fuel being returned so don't skimp on the filter set up.

I will be running red stuff, so I know what I need now. 30 microns.

Thanks for the input gentlemen.

BTW- buy the primary filters by the case, can't have too many aboard.

good to see vicroy answering questions! you have that throat issue beat i hope.