Martin Russell had a happy return to the UCD Bowl as Limerick piled the pressure on his former club.
Two goal from Rory Gaffney and a third from Ian Turner secured Limerick's fourth win in eight games, as UCD's winless run was extended to eight matches.
The Students remain in the relegation/promotion play-off spot with just six games remaining.
A flowing Limerick move saw them open the scoring after 13 minutes. Lee Lynch fed Gaffney, his pass wide found Turner in space, and he returned the favour, crossing for Gaffney to head into the bottom corner.
UCD started the second half well, and Ayman Ben Mohamed forced Barry Ryan to save well with his feet before a crazy spell of three goals in seven minutes.
Limerick doubled their lead just before the hour, Prince Agyemang's pass split the UCD defence to find Gaffney, he turned Ian Ryan to finish under O'Donnell.
UCD then got one back through Conor Cannon on 63 minutes before Turner's low shot made sure of the points two minutes later.
UCD: O'Donnell; Matthews, Douglas (Kavanagh 69), Ryan, Coyne; Molloy, Creevy, Sloggett (Burke 76), Ben Mohamed; Benson; Cannon (Belhout 66).
Limerick: Ryan; Nzuzi, Leahy, Williams (Whitehead 69), S O'Connor; Turner, Lynch, Agyemang (Tracey 74), Duggan, Doherty (Djilali 80); Gaffney.
Referee: A Buttimer (Cork).