This is starting to look more like the pleasure boat with diesel power
application. But cars don't typically have to deal with the shaken-up
sediment load - and it is this that has been a continual preoccupation
in this newsgroup thread.

It is this that this trhead is addressing. We have a diesel bus for our
business
and have had no problems with the fuel problems we have had on our boat.
Preoccupation seems to have a negative connotation in that it generally
infers that the issure is not necessarily real or is blown out of
proportion.

For people who are willing to consider reasonable approaches to diesel
fuel handling (and gasoline for that matter) there can nobody who
can pick fault with using a sampling valve at the low point of a fuel
tank. This can save so much grief from water and visible
contamination that it represents ultra-cheap insurance.

Unfortunately, a sample valve at the low point in a fuel system is
very much in violation of CG rules. That said, my tanks have them
and I wouldn't be without them.

The next reasonable step is to provide a sight glass for early
detection of water and contamination (the 'tractor' approach)


The transparent bowl in a Raycor fills that bill.

For people who just cannot fit a drain/sampling valve in a sump
(though they cost under $20 typically) and have some reason to avoid a
sediment/water sight cup then using a pair of surface filters offering
large area and rotating them will save most engine outs - but not all.

For people who must do all they can to eliminate engine stoppage from
fuel contamination, then fronting a fuel system with a depth filter
that won't itself break down is cheapish insurance.
I haven't surveyed depth filters in this application recently -
but the ones that no expert could not reasonably object to would be
built something like this:
layered stockinette knit,
string bobbins.

In reviewing what I have written here today, I see I have omitted any
mention of fuel polishing - which is where the thread started.

Here's my personal opinion on this:
boaters and sailors will know if they are likely to get fuel
contamination - it only takes one nasty experience.

The realistic view is that it is not 'if' but 'when'. Bad fuel can be
obtained
anywhere. But what is the reality it that fuel can go bad just sitting in
the
tanl. So the best supply of fuel in the world will become bad. Sailboats
are especially prone to this since we tend to use little fuel.

They will think that if they replaced all fuel tanks and took on
only clean dry fuel, they could avoid another scare - but that's not
practical for most (and even those who did could still find water in
the fuel - temperature cycling in a ventilated tank can *deposit*
water in the fuel, for sure.)

Water is easily removed by a normal Raycor. It's the water that provides
the interface for critters to grow that becomes the problem.

These are the people who could consider fuel polishing.
So the question is: does fuel-polishing work?

Yes.

I don't see how you can avoid the conclusion that a reasonable
fuel-polishing design makes things better - if not perfect.

Nothing is perfect, that is fur shur!

So I would not want people to confuse the idea of polishing fuel
with the idea of paper depth filters - the two ideas don't have to go
together. It seems to me you can polish perfectly well with surface
filters.

It appears you can. But the filters do not last nearly as long.

Arguably, the surface filter, which might block with sediment is
*still* OK in a (by-pass) fuel polishing layout. If it blocks - so
long as you know it, it does not stop you dead (yet) so long as you
get some warning that the bypass is blocked and the same is likely to
hit the main fuel filtration soon.


My vision of a polishing systemn is that it is iundependent of the engine
system. But I suspect that the engine system will block prior to a
polishing system if the polishing system is not adequate.

What you positively don't want is a main fuel feed blocking.
So strangely enough, I think a depth pre-filter is *most* helpful
here. And it is reasonable to take account of objections to
unbonded paper filter media if they can decompose in water.
Ithink a separate polishing system is better. Prefiltering may lead
to lift-pump failure as things clog up.

As a labor of love, I'll take a look around to see what industrial
depth filters may prove helpful in this application.

Thanks! Much appreciated!

Brian W