Fuel Filters

[Mike]

Took last Friday and changed both fuel filters. My question is: should they both be changed at the same time? I had a hard time getting her to stay running.

[Mariner]

That depends on how the filters are set up. Are you talking about primary and secondary filters where it goes through one filter before the next? Are they parallel where fuel runs through both at the same time (to accomodate higher capacity)? Or are they on a manifold so that you can switch between the two and run either one or both at the same time?

[Mike]

They are primary and secondary filters and runs through both at the same time.

[jcollins]

Mike,
Are you still having problems? I'm getting ready to change both of mine this weekend.
There are a few threads on the board about fuel filters.

[Mariner]

Ok, the primary filter is the one that is on the engine, the secondary is the one that is mounted elsewhere. This confuses a lot of people because the fuel usually passes through the secondary filter before the primary filter. But that's the generally accepted way to identify them. Just thought I'd start with that so we're all on the same page.

In many cases, the secondary filter has a finer element than the primary filter, and it's generally not necessary to change the primary filter very often. Some people simply never change it. I don't think that's a good policy, but in these cases, you can certainly go years without changing it.

In my opinion, the primary filter's true role is just to catch contaminants if the secondary filter fails.

[Richard]

Mariner:

Based on everything I have read in Passagemaker magazine (they have had a lot of stuff recently on fuel systems) the primary is closest to the tank and usully has a "coarser element" (30 Microns is typical). The secondary is on the engine and is typically "finer" (5 microns). This is exactly the opposite of what you wrote. Some people prefer dropping the primary down to 20 or 10 Microns but never less than the secondary on the engine.

On my boat the primary is a 30 micron Racor and the secondary is a Yanmar part (5 microns I think).

[Mariner]

Interesting. From what I've seen, most people do it the way I mentioned. And the reason the filter on the engine is called "primary" is because it was the one that shipped with the engine and can be relied upon for filtration if needed. The secondary filter is one that is added by the boat manufacturer or owner, hence the term "secondary". The idea with a finer (1, 5, or 10 micron) filter element in the secondary filter is that these filters (usually Racor) are higher quality and easier to change, therefore should be relied upon as the primary means of removing contaminants from the fuel.

[jcollins]

Now I'm confused.

[Mariner]

Now I'm confused.

It's confusing. I suppose we should agree on the nomenclature to avoid confusion.

I'm ok with calling it whatever.

[N4QC]

Check out the following links for primary, secondary or “last chance” fuel filter designations.

Recommended filter size, function, and frequency of change are other issues, and are dependent on manufacture’s recommendations and local operating conditions.


http://www.yanmarhelp.com/i_fuel.htm

Article: Marine Fuel Filtration - 'The Seaboard Way', at Boatdiesel.com, by Tony Athens, April,’06.

Hope this helps...

[TD]

I don't know about Yanmar. Cummins techical hot line recommends 30 micron on the Racor and the Cummins primary is 10 microns but not advertised. My experience on diesel is if you use 10 microns on the racors you will be changing about every 100 hours.

[Mike]

John -
No problems now. The next day when I cranked her over, she cut out then started right up again and ran like a champ. With this info I know now that changing both isn't necessary. Thanks to all.

[chiefrcd]

Filter 1 collects the big hunks and filter 2 collects the little hunks and by the time you collect all the hunks you hope you've clean you're fuel enough to work properly. I change both filter 1 & 2 when I change my oil and filter....every year or every 100 hours, which ever comes first. All of that is cheap insurance to keep my very expensive diesel running.

[Merry Kate]

Go to boatdiesel.com and read Tony Athen's article on fuel filtration. He's as good as they get.

[DougSea]

Go to boatdiesel.com and read Tony Athen's article on fuel filtration. He's as good as they get.

And to quote a brief snippet from his article:

"The Tankage or Holding Methods your vessel-older fuel tanks will typically have something in the fuel tank that that you do not want your engine to burn or get anywhere near the "on-engine" or last chance filter that is part of the engine fuel system. Whether it is be some type of growth (algae), accumulated "mud" (diesel fines, sludge build-up, etc), rust flakes (from older steel/iron tanks), water, internal tank coatings that are deteriorating, or ???, there is always something in there that should not make it past your OFF-ENGINE / PRIMARY fuel filter system"

So based on the last sentence I'm going to stick with the "Primary" as the big Racor which my fuel flows through first and the "Secondary" as the on engine filter which my fuel passes through second.