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DIESEL FUEL ... Keeping It Clean                                              Marshall Solomon, Marsh Marine         I    am   often   asked,   “What   can   I   do   as   a   boat   owner   to   keep   my   diesel   fuel   clean?”       Without   clean   fuel   your boat   is   not   dependable,   safe,   or   fun.      Maybe   you’ve   been   lucky   and   never   been   stranded   by   clogged   fuel filters,   but   have   no   doubt,   when   it   does   happen,   it   will   be   a   very   bad   day   boating!      Furthermore,   with   the cost of fuel rising, this issue is becoming ever more important. I n   previous   articles,   I’ve   written   about   what   can   happen   as   fuel   ages   and   sits   for   extended   periods   of   time.   If you’ve   followed   these   stories,   then   you   know   there   are   two   major   contaminants   which   can   spoil   your   fuel; water    and   sludge .      Notice   here   that   I   have   not   listed   Algae .      I   hope   by   now   most   of   you   have   learned enough   from   my   articles   to   know   that Algae   cannot   exist   in   your   fuel   or   tank.      The   term   is   often   incorrectly used   to   describe   the   black,   gooey   mess   that   typically   is   found   in   your   fuel   filters.      This   is   not   Algae;   it   is break down fuel and is actually a substance called Asphaltenes . W ater   is   probably   the   worst   contaminant.      Water   will   do   serious   damage   to   your   fuel   delivery   machinery, namely   your   fuel   pump   and   certainly   your   fuel   injectors.      Injectors   are   meant   to   spray   diesel   fuel   into   the engine’s   cylinders   under   extreme   pressure.      This   spray   must   be   so   fine   that   is   it   is   virtually   a   vapor.      Too heavy   a   spray   and   the   fuel   will   not   ignite.      To   accomplish   this,   the   injectors   have   spray   nozzles   which   have minute   holes   in   them.      Depending   on   the   type,   these   holes   usually   range   in   size   from   7   to   10   thousands   of an   inch   in   diameter.      Visualize   holes   which   are   just   twice    that   of   a   human   hair!      If   water   is   pumped   through these   hot   injector   tips   the   holes   become   eroded   destroying   the   tip’s   ability   to   create   a   proper   vapor   pattern. Sometimes   the   water   will   crystallize   the   tip   rendering   it   useless.      The   point   here   is   that   water   can   cause serious   and   expensive   engine   damage.      Most   of   the   time   water   in   the   fuel   will   settle   to   the   bottom   of   the tank.      Here   it   can   be   removed   without   damaging   the   fuel,   but   it   can   also   become   so   mixed   into   the   fuel   it becomes   homogenized.      When   this   happens   it   will   never    separate   from   the   fuel   and   all   the   fuel   must   be discarded.      Water   homogenized   fuel   has   a   milky   pink   color   (See   photo   1).      This   is   the   most   damaging   fuel contaminant.  Run it long and you will destroy your fuel delivery system.    T he   next   and   most   often   found   contaminant   is   sludge.      I   use   sludge    as   a   collective   term   for   it   can   be   either inert    or   biological .      Biological   sludge   is   caused   by   bacteria   and/or   fungi   growing   in   the   diesel   fuel   where water   is   present.      Believe   it   or   not,   but   this,   from   my   experience   in   having   cleaned   hundreds   and   hundreds of   tanks,   is   actually   rare.      It   cannot   occur   without   the   presence   of   water   since   this   is   needed   for   the biological   to   obtain   oxygen.     Though   rare,   this   is   another   very   bad   condition   to   clean   up.      Inert    sludge   is   the most   commonly   found.     This   brown   to   black   goop   is   what   has   become   known   as Algae.      It   seems   to   be   alive since   it   appears   to   grow   in   the   fuel.     This   “growing”   process   is   really   microscopic   fuel   components   breaking down   and   forming   larger   clusters.      This   clustering   tendency   is   called   agglomeration    and   as   previously stated,   is   Asphaltenes    (See   Photo   2).      Call   it   what   you   might,   this   is   the   substance   most   often   found   in   your fuel.  Fortunately, it is the easiest to prevent.  Let’s see how: