3.0d reluctant start after long trip

[Clownshoe]

So just finished a 3000km trip towing a trailer and doing some high average speed runs. Lots of gravel roads, lots of eating dust.

She used to start on the first turn, now you may have to try twice or a longer crank the first time.

What could it be. Airfilter was new before trip. Car was serviced just before leaving.

 

[netercol]

cranking speed still the same? (meaning the starter is not turning slower than it used to, diesel needs to reach certain rpm to start)

fuel pressure? might have low rail pressure at start due to dirty fuel filter?

cant think of more right now..