Diesel polishing
hole to be cut in the top of the tank:
when I inserted the standpipe it
had touched the side of the tank,
which felt ‘furry’. My response on
that occasion was to fit a separate
filter just for the heater’s newly
re-piped supply, although in
hindsight that was a hasty action
and not a solution. It was
suggested that I should discard
the fuel, steam-clean the tanks
and start again, but that seemed
excessive. I searched online for
fuel containers, but decided this
was too lengthy and expensive a
solution, and not really feasible in
my situation.
The tank lids were made of
stainless steel: I was willing to fit
the innovative Wema tank lids from
Tek-Tanks, but was worried about
what I might find under the plates if
the orifice was not a 112mm round
hole, and the six plates appeared
to be screwed into place with
Sikaflex sealing compound. I
believed that I needed them to stay
sealed, at least until I got back to
base in Lowestoft. Next, I searched
Google for advice about dealing
with fuel tank contamination, but
found nothing directly relevant to
me, given that I was not a bulk
fuel user with 1,000lt tanks, nor
was I presenting a significant
environmental hazard.
However, I came across a term
that, although I had heard it before,
meant little to me. Only two weeks
previously, Andy – a visitor to
The blocked filter
A filter bowl cracked during the 101-mile motor-sail home
I replaced the pretty clean Crosland filter with this Fram filterPBO verdict
A good investment
To build a DIY system, a small
diesel polishing filter with a
140lph circulating pump can
be bought online for less than
£100: professional systems
can cost in the region of £500,
but would seem to be a good
investment even at commercial
prices. I have been advised that
a small solar panel connected
to the pump should suffice to
protect the fuel over the winter
when moisture allows the
bacteria to grow rapidly.
The diesel bug problem
was initiated when biodiesel
began to be added to the fuel
back in 1998. Biocides like
Marine 16 products quickly killthe bugs, which then
coagulate and stay in clumps
in suspension but in a low
layer in the tank. The answer
quite simply is a turbine filter
with a pump for use especially
when the engine is not running,
and maybe when any fuel
sediment has been stirred up.
It seems obvious now that
a blocked filter will almost
inevitably result in an engine
stoppage unless the fuel is
cleaned. When in the RAF,
my flight sergeant in basic
training used to say ‘shiny
shoes is happy shoes’:
and ‘shiny diesel is happy
diesel’ is equally applicable.Lowestoft on another Colvic
Watson – had shown me
his comprehensive engine
management systems including a
fuel-polishing filter. I had not really
grasped how this could be such
a critical part of the overall fuel
management system, but was
beginning to realise the truth of it. I
searched online again and found
the family-run business http://www.
dieselpolishing.co.uk: the
company’s Allen Blake (a friendly
Yorkshire boat owner) was willing
to help me, and drove down from
his base near Leeds. He twice
filtered the entire dirty contents of
my tanks with the system pictured
below, agitating the contents with
the returning fuel over a period of
four hours. The black sludge-like
layer at the bottom of the tank had
settled somewhat over 48 hours
but only contained mostly dead
diesel bugs that had coagulated
and made the filter bowl look
like a shaken snow globe, exceptThe system shown here was used
to twice filter the entire dirty
contents of my tankswith black snow falling.
The black stuff was easily
removed, although not all at once
as the filter in Allen’s system would
have been blocked quite quickly. A
tiered approach gradually cleaned
it up. We only had to discard 9lt of
liquid, and some of that could have
been recovered or recycled if we’d
had more time as there did not
seem to be much water in it.
After only four hours’ work I had
300lt of shiny red diesel back in
my tanks again and ready to flowthrough yet another new filter, a
Crosland one this time. I motor-
sailed the 101 miles back to base,
stopping the engine after 20 hours
and 20 minutes with plenty of
diesel left in the tanks. I found
that a filter bowl was cracked and
went to ASAP Supplies for a
replacement, changing the pretty
clean Crosland filter for a Fram.
Now, the only weak point left in the
fuel system is the banjo bolt on the
top of the Iveco engine-mounted
filter, and that is on order.