Both sides saw penalties saved as Paul McGuinness' youngsters shaded an entertaining encounter and, after the surprise 3-0 midweek defeat to Everton, it was important that the visitors got back on track against the bottom team.
The Reds made the perfect start when a well-worked corner, Callum Evans flicking on Andreas Pereira's centre, allowed Ioannou to convert a close-range header with only seven minutes gone. Palace were fortunate not to fall further behind when Tom King saved a Sam Byrne shot and the rebound deflected off Kiran Khindra John and clipped the woodwork.
Byrne then had a goal ruled out for offside and the hosts emerged as an attacking force themselves. Reise Allassani fired wide from a Javen Palmer pass but hit the target with his next opportunity to level the scores. Allassani robbed Paddy McNair and slotted past Pierluigi Gollini with the aid of a slight deflection.
Palmer had a couple of attempts either side of a golden opportunity that was spurned by James Wilson but United finished the half on top. King made a good stop to deny Wilson from a tight angle and the speedy striker crossed well only for Byrne to get his finish all wrong from an unmarked position.
The chances kept coming thick and fast after the restart with Byrne blazing over a volley when a goal seemed certain and forcing a smart stop out of King. There was drama in the 55th minute when a penalty was harshly awarded against Luke Croll when the ball bounced against his arm. Wilson's spot kick was superbly saved by King to keep the score at 1-1.