Alan McGreal scored the pick of the goals as a dominant first half display earned Crumlin United a passage through to the quarter-finals of the Extra.ie FAI Cup.
The Leinster Senior League champions thus enter Monday's draw live on Morning Ireland as the only non-league side left in the competition.
LSL Division 1A winners Lucan started brightly at Armagh Road with Marco Chindea having a half chance before they really should have been ahead on seven minutes.
Aji Sule put Andrew Bracken through one-on-one with Michael Quinn. But the Crumlin keeper outfoxed the Lucan attacker to make a fine save at his feet as Bracken attempted to take the ball around him.
Crumlin responded with Dean Kelly wastefully blazing over the top from a Craig Walsh cross from the right flank before taking the lead in the 10th minute.
Gareth Brady whipped an in-swinging free kick into the back post where unfortunate left-back Shane Maloney turned the ball into his own net.
Crumlin doubled their lead from a harshly awarded penalty eight minutes later after Kelly's cross struck the hand of Boby Mazono.
Jake Donnelly found the corner of the net from the spot, but not before Ian Molloy got a hand to the ball having gone the right way.
Molloy then made a blinding point-blank save to deprive substitute Liam Brday on 35 minutes after Walsh and Donnelly worked the opening.
A terrific save at the other end two minutes after that kept Crumlin two goals ahead. Bracken put Chindea in on the left with Quinn standing up superbly to parry away the fiercely struck drive.
Four minutes later Curmlin added a sublime third goal. Skipper Thomas Hyland's deep diagonal ball completely flummox Lucan.McGreal’s delightful first touch teed up the left-foot finish that flew past Molloy.
Though McGreal cracked a shot off a post just before the hour mark, Lucan had more about them from the resumption.
Tayem Dinamunengo had a drive cleared off the line by Noel Cummins on 62 minutes.
Seven minutes later Lucan got a goal back. Paddy Seery met central defensive partner Sean Cronin’s deep free kick to score with a header that hit a post and went in off keeper Quinn.
Back at the other end, Molloy prevented a fourth Crumlin goal with the save of the game on 71 mnutes, spending himself well to parry away a shot from winger McGreal.
Crumlin United: Michael Quinn; Noel Cummins, Thomas Hyland, Blair Mandiangu, Gareth Brady; Craig Walsh, James Lee, Conor Murphy, Alan McGreal (Sam Burgess 79); Jake Donnelly (Gingi Aki 84); Dean Kelly (Liam Brady 23).
Lucan United: Ian Molloy; Boby Mazono (Azeez Yusuff 88), Sean Cronin, Paddy Seery, Shane Maloney; Aji Sule, Michael McLoughlin, Tayem Dinamunenga, Marco Chindea; Andrew Bracken; Harmony Mercer
Referee: Barry Fitzpatrick (Dublin)
