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  Topic Review (Newest First)
08-05-2009 11:10 AM

Thank you for your help. Everything went off w/o a hitch (although it's a good idea to turn the fuel back on before you bleed the system - don't ask me how I know.)
08-04-2009 03:45 PM

The Primary Fuel Filter is the Filter on the Engine, the secondary is a separate from the motor. The primary is small filter (usually) Some folks only run a primary.

The secondary is either a fuel only or a fuel/water separator filter. A Racor Fuel/Water Separator has a clear plastic bowl screwed underneath a cartridge fuel filter. The fuel filter looks like a car oil filter except it has an open top and bottom. The function of the secondary filter is to separate out the big chunks of crud and any water in the fuel. Water is heavier than the fuel so it collects in the clear bowl at the bottom of the assembly. Once the fuel is "cleaned" of the big junk and water, the primary, on your motor, polishes it before it goes into the injectors. The Secondary may have a 30 micron rating, whereas your primary may have 10 or 20 micron.

As far as the method that you need to do change your filters, its boat specific. However, it is best to remove all of the air from each filter first instead of doing a full system bleed. If you don't get the air out of each filter assembly first, it may take a awhile to push it all out. This why I recommend that you fill each filter as much as you can with new fuel before you reassemble. Reduces the amount air that you need to bleed.

08-04-2009 11:52 AM
I'm a little confused (not an unusual state for me)

Isn't the filter closest to the fuel tank the primary filter?

Will the filter closest to the fuel tank fill up w/o pumping if it is lower than the fuel tank? (I don't remember a separate pump on it - it's not a Racor)

So there is no advantage to changing/bleeding each filter separately?

Thank you VERY much for your help!

08-03-2009 10:07 PM
Sort of, here is my list

Okay, I don't have the same motor as you, but I do have a Yanmar with a primary and Secondary/water separator. Here is what I do.
  1. Engine is off.
  2. Place small bucket or a bunch of absorbent under the secondary filter/water separator
  3. Remove Water/Secondary Fuel filter. Dump fuel in fuel/separator in a waste collection container. Replace filter.
  4. Fill filter with clean diesel until almost to the top. Screw assemble (filter and water separator bowl)
  5. Open bleed screw on top and unscrew pump handle - This is on my Racor assembly, yours maybe different.
  6. Pump handle on filter until no more air comes out of filter. Tighten air blled screw.
  7. Repeat the process with the primary fuel filter, except pump the air out with the Manuel fuel lift pump before the primary filer. Don't for get to bleed air from the top of the primary fuel filter housing and just before the injectors.
  8. Wipe down the motor of any spilt fuel and dispose of the waste fuel/rags/diapers in the proper manner.
  9. Fire motor for 10 to 15 minutes to insure than no air is in the lines
08-03-2009 05:57 PM
Fuel filter change

I have a Yanmar YSM8 that needs its fuel filters changed. What Id like to do is go through the steps as I understand them and get some input from members.
Here goes:
1) Cut off the fuel at the tank.
2) Place cut off gallon milk carton beneath filter.
3) Clean around primary filter.
4) Remove water separator and filter.
5) Clean thoroughly and put old filter in ziplock bag. Put in 5 gal bucket.
6) Inspect O-rings. Replace if necessary.
7) Install new filter. Do not replace fuel as this might introduce impurities downstream of the filter.
8) Open bleed screw.
9) Turn fuel back on.
10) Use thumb lever pump to fill filter and bleed air.
11) Close bleed screw when no more air comes out.
12) Run engine for 10-15 minutes to insure that engine was properly bled.
Repeat process for secondary filter.
What did I leave out? If I follow these steps, is it all right to fill up filter with fuel since any impurities will be caught by the secondary filter then just not fill up the secondary filter?
Dahlgren, VA

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