The 24-year-old Lancashire batsman had reached 87 not out by close of play on the opening day of the tourists' match against Border at Buffalo Park but was then kept waiting by yesterday's complete wash-out.
It took him another 75 minutes this morning to eke out the additional 13 runs needed for a century that can only boost his hopes of playing in Thursday week's first Test against South Africa.
By the time he reached three figures, Crawley had been batting for six hours in all. His innings included 10 boundaries and followed an equally diligent 85 in Soweto last week.
Crawley's only real moment of concern this morning came on 91 when he attempted to sweep off-spinner Peter Emslie and survived a loud lbw appeal.
While the stand-in opener inched forward with just eight singles and a two in the first hour before on-driving a boundary, Jack Russell made sprightly progress after England had resumed on 218 for four.
Having started with 16 to his name, the wicket-keeper advanced smoothly to 48 as the tourists reached 272 without further loss.
Because of yesterday's blank, both teams had agreed to extended hours of play over the final two days.
The match resumed half an hour early this morning and was scheduled to finish 30 minutes later than originally planned.
England could do with as much match practice as possible after their weather-hit start to the tour.
There seemed little chance of engineering a victory at Buffalo Park, but improved conditions at least offered the hope of pace bowlers Darren Gough, Dominic Cork and Peter Martin getting a decent work-out for the first time on tour.
Russell survived one chance when edging a cut against Emslie into - and out of - Piet Botha's left hand at slip.
But he also played some sparkling shots and reached a 110-ball half-century with his fifth boundary by straight driving young fast bowler Makhaya Ntini.
Crawley's marathon stay ended on 108 when he went half-forward to Brenden Fourie and was hit on the pad and adjudged lbw.
He had batted for a minute short of six hours, faced 281 balls - 65 of them this morning while adding 21 runs - and struck 10 boundaries.
That dismissal ended a partnership of 96 and gave Cork a chance to have only his second bat of the tour.
England had no plans to declare before lunch. With the interval less than an hour away they were 297 for five.
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