[C320-list] ENGINE FUEL PRIME

[Jeff Hare]

Troy, 

That's a really good list.  There's an alternative to #2 which we did for 20 years in Woodbine.

We always ran an R15S filter in the primary Racor and the Yanmar recommended 10u(?) engine mounted filter and changed the Racor every year.

The R15S is a 2u filter. If you end up with a clogged filter, you can be fairly certain that you only need to change the Racor to get running again.  The engine mounted filter is intended to be a safety for anything that slips by the primary Racor during fuel line servicing or primary filter change that would be damaging to the injectors. The tech from Mac Boring and our local Yanmar dealer/installer/mechanic at Merri-Mar both explained the same thing to me independently back when we bought our boat.

Instead, if you follow the old-timer's advice of going with 15u or 30u filters in the Racor, followed by the stock Yanmar engine filter, you can be fairly certain that if you ever get a clogged filter, you'll have to change both the engine and the Racor filters. Filters don't tend to clog at the dock, so that's a lot more work underway and probably in unkind conditions. You could also find that the engine filter (having so much less surface area) will get fully clogged well before the Racor and you still wouldn't know for sure whether you needed to change the Racor as well or not.  

The R15S filter allows a much higher fuel flow rate than the fuel pump can move anyway, so there's little concern of starving the system. Using this approach, we changed the Racor every season and only changed the engine mounted filter every 3 or 4 years and the one we removed appeared just as clean as the one we removed. The Racor was always discolored when changed. In a large Diesel that moves a ton of fuel, this could be more of an issue.

We also installed a shutoff valve at the outflow side of the Racor so that we could isolate the Racor when changing it and minimize the chance of getting debris in the line during the change and make it far easier to bleed. Anything that did get in the line during that would either be stopped by the engine filter or is small enough to safely pass. 

That's worked flawlessly for us for 20 years owning Woodbine.

One thing we had considered was putting an inline vacuum gauge between the Racor and the fuel pump to get a better sense of when the filter needed to be changed, but a bright flashlight through the clear bowl has worked well enough (but decidedly unscientific). Just something I never got around to and never actually needed.

-Jeff Hare


-----Original Message-----
From: C320-list <c320-list-bounces at lists.catalina320.com> On Behalf Of Troy Dunn
Sent: Monday, May 9, 2022 7:45 PM
To: C320-List at catalina320.com
Subject: Re: [C320-list] ENGINE FUEL PRIME

John-

Free advice in no particular order.

1) There are copper crush washers between all the banjo fittings.   These
are super cheap and throw away.   Attempting to reuse and/or tighten them
down rarely works out, or if it does only for a little while.

2) Change the smaller filter on the engine once a year.   Is it 100%
necessary, no but it's super cheap and super easy.  Do not attempt to reuse
the oring.   Seat the filter by hand then just gently put the oring and
filter housing in place, tighten that little band by hand and then gently (very gently) tap the band home with a flathead acrewdriver.  You just need to snug it up, do not over tighten.

3) bleed seal is a nylon like material.   It is reusable so long as you
simply get it snug and then gently 'nip' it a fraction of a turn like maybe a tenth of a turn.  Overtightening will turn that seal into a once and done
as well.   Definitely replace it this time since you probably don’t know
how it was abused in the past.

4)I’m a tad concerned that you are losing as much prime as you are and that you aren’t finding diesel somewhere on your engine or in your engines
special little self contained bilge area.   The fact that you hear air
escaping is not a good sign.   Are you sure it isn’t the diesel return line
you hear?   Probably not since you are saying the noise is on the starboard
side.    The fuel filter is a good candidate for leaks but generally it
will be very ‘oily’ with diesel and should drip noticeable.   Another item
that can leak is the fuel lift pump.   There are two possible mechanisms at
play.    There is a diaphragm that can leak at the seal.    Check that for
sure.  It’s  easy to simply replace the lift pump.  The lift pump diaphragm can also fail and that can be bad news because it could potentially be
leaking fuel into your engine.   I think you can check the oil to see if it
looks funny.  If it does look funny,  I’d get a real diesel mechanic involved.  You can easily replace the lift pump and contaminated oil but I have no idea how one 'rinses' out the engine of fuel contaminated dirty oil…

Good Luck

Troy Dunn
Hull #514