Al Hilal, who have won the continental competition on two occasions, enjoyed the better chances in front of more than 63,000 supporters at the King Fahd International Stadium on Tuesday.
And they were duly rewarded in the 71st minute thanks to Al Faraj's unstoppable strike.
The hosts enjoyed the majority of possession in the first half, but the visitors nearly took the lead when Mohammed Kasola forced a great save from Abdullah Al Sudairy on the stroke of half-time.
Nadir Belhadj went even closer for the away side in the 70th minute when he forced Al Sudairy to tip his strike onto the crossbar.
That save proved crucial as the Saudi team scored a minute later, Al Faraj drilling home from the left of the penalty area.
Al Hilal will now travel to Qatar next Tuesday with a slender advantage.
