Ilan earned the Irons a point at Everton last weekend and he was on target again this afternoon as Gianfranco Zola's side edged four points clear of the relegation zone.
Ilan was virtually unknown in England when Zola signed him from St Etienne on deadline day in January but he is quickly endearing himself to the Upton Park faithful.
The Brazilian was promoted into the starting line-up for this game and he made the telling contribution after 51 minutes when he latched onto Carlton Cole's downward header to earn West Ham their first win in eight games.
West Ham are still far from safe but this result, combined with Burnley's victory at Hull, means Zola will be breathing easier tonight.
Valon Behrami also came into the West Ham side, in place of the suspended Scott Parker while Sunderland were unchanged following their impressive 3-1 win over Tottenham last week.
For 10 cagey minutes neither team was able to create an opening, with the game played almost exclusively in the middle third.
Ilan turned cleverly in the centre circle but his pass for Cole was easily picked off while Anton Ferdinand's cross was just too high for Frazier Campbell at the other end.
But it was the Black Cats who did start to take control as Steed Malbranque grew increasingly influential on the left of midfield.
Malbranque engineered the first threatening attack of the game as he exchanged passes with Kieron Richardson to earn Sunderland a corner - and they should have taken the lead.
West Ham defender Manuel da Costa failed to deal with Malbranque's inswinging delivery but Campbell could not latch onto the loose ball as it ran across the six yard box and the Hammers survived.
Da Costa redeemed himself with a timely intereption as Malbranque attempted to slide a pass through to Bent, who would have been through on goal.
West Ham were struggling to keep Bent under control and the Sunderland striker latched onto a long ball over the top only to see his attempted lob over Robert Green land on the roof of the net.
Behrami then had West Ham's first shot on goal, forcing Gordon into a low block, and Richardson was on hand to clear his lines as Junior Stanislas loked to pounce on the rebound.
West Ham began to build pressure but Cole could not get a shot away after stripping David Meyler of possession and Ilan was judged to be offside after being picked out unmarked on the edge of the box by Jonathan Spector.
Lee Cattermole was booked for a late challenge on Behrami but Mark Noble's free-kick was poor and Sunderland counter-attacked, with Malbranque feeding Bent whose low strike was straight at Green.
Sunderland then received two major let-offs in the space of five minutes and were fortunate to reach half-time on level terms and with 11 men still on the field.
Firstly, Craig Gordon was penalised for handling the ball outside of his area but he received only a yellow card and West Ham made a hash of the free-kick.
Sunderland then had Paulo da Silva to thank for a brilliant interception inside his own box, stealing the ball from Ilan's toes after he had been picked out by Cole.
But if Gordon had been fortunate with the hand-ball, he was the luckiest man inside Upton Park after dragging Cole to the ground inside his box only to be saved by the whistle of referee Mike Jones.
Gordon had panicked after dropping a high ball while under pressure from Cole but referee Jones had already decided to penalise the West Ham striker for a foul.
When Meyler was judged to have fouled Ilan on half-way, referee Jones called Sunderland captain Michael Turner over to warn him about the Black Cats' discipline.
West Ham exacted the perfect punishment. Da Costa launched the free-kick towards Cole and Ilan latched onto the knock-down to score his second goal in two games.
The explosion of noise around Upton Park was as much relief as celebration.
Sunderland responded calmly, dominating possession and passing the ball around to stretch West Ham and test their patience but Cattermole's drive whistled just wide of Green's right-hand post.
Sunderland sent on Kenwyne Jones for Meyer and he made an immediate impact with a driving run from midfield before sliding the ball towards bent on the edge of the box.
The Sunderland striker took a perfect first touch to tee up the shot but he slipped on the Upton Park turf and Green was able to scramble out of goal and smother the ball.
There was drama right to the death. In the fourth minute of added time, Franco had the ball in the net and wheeled away to celebrate.
But the Mexican was judged to have controlled the ball with his left hand and the goal was disallowed. Thankfully for West Ham, it did not matter.