Sylvain VAN DER WALDE wrote:
"Grumps" wrote in message
...
squelchy wrote:

snip


OK. Our local garage (not BMW main dealer) has checked all possible
issues and has found nothing! Of course, the engine starts perfectly
at the moment.


One thing they noticed was that the fuel filter is new(ish), and
wondered if there was a fault with this or its fitting.

That's a possibility. I would check it out.

How exactly does a fuel filter work, and what would cause it to
sometimes stop the engine from starting?


The frequent enemy of a diesel engine fuel system is _air entering
it_. In the case of filters, there usually is a round detachable housing
which is sealed by a rubber ring. You should _always_ replace that
ring (supplied with the new filter element). Sometimes several
different rings are supplied, and you should compare the new one with
the old one. This rubber ring is not always easy to fit, and I always used
a
mirror to make sure that it was seated properly. The assembly that
the fuel element housing fits to has usually an input connection and
an output one. These don't normally give problems, but _sometimes_
they do (they allow air to come in). Cleaning these joints with
petrol, drying carefully, and using some jointing compound (red
hermetite is ok) on all the threaded parts, etc.. will usually work.
I don't normally endorse using jointing compound, unless a part is
unobtainable or excessively costly.

Hmm. The BMW main dealer must've replaced this filter. You'd think they'd
know how to do it!
However, I'll get them to check.

Would this "fitting error" (if it is an error) cause an intermittent
starting problem? The engine runs perfect otherwise.