function split(src,dec : string):TStringList;
var
i : integer;
str : string;
begin
result := TStringList.Create;
repeat
i := pos(dec,src);
str := copy(src,1,i-1);
if (str='') and (i>0) then
begin
delete(src,1,length(dec));
continue;
end;
if i>0 then
begin
result.Add(str);
delete(src,1,i+length(dec)-1);
end;
until i<=0;
if src<>'' then
result.Add(src);
end;

procedure TForm1.Button1Click(Sender: TObject);
var
ss : TStringList;
str,dec : string;
begin
str := '1111||2222||||3333|||4444||';
dec := '||';
ss := split(str,dec);
memo1.Lines.AddStrings(ss);
ss.Free;
end;