Referee Ryan Shepard judged Demons defender Matt Pressello to have fouled Jelen in the 94? minute and amidst a sea of protest the Brazilian held his nerve to outfox Ivan Necevski to give the Rams a scarcely deserved share of the spoils.
Blacktown City Demons striker Bruno Salas opened the scoring a minute before halftime with a thumping strike that raised the roof in Seven Hills.
After being played in following a piercing run from Brendan Maroney, Salas lifted the ball past Brody Crane from 23 yards to give the home side a deserved lead as they headed to the sheds.
Whatever Ken Schembri said to his players midweek had the desired effect with the Demons dishing up a much improved performance after their shambolic effort against Manly United FC.
Former Queensland Roar and Perth Glory A League utility Jordan Simpson was drafted into the run on side after returning from overseas trials and despite lacking match fitness displayed some deft touches in the opening stanza.
Daniel Wilkinson almost broke the deadlock on 12 ?minutes after bending his free kick against the near post with Crane well beaten.
The Rams? Jason Lewis should have tested Necevski thirteen minutes later after being clear on goal but lost control of the ball at the vital moment and the chance went begging.
Wilkinson again tested Crane seven minutes after the interval when he whipped in a dipping free kick which the Rams custodian did well to parry over the crossbar for a corner.
Ivan Necevski then showed why he is on Sydney FC?s books with two top shelf saves in the 59? and 75? minute to maintain the Demons one goal advantage.
He reacted well to thwart Jelen at his near post before producing a world class fingertip save to deny Michael Brown?s firmly placed header which looked destined for the bottom corner.
Wilkinson then ensured the Demons would finish the match with ten men after being sent off following a second yellow card with ten minutes of regulation time remaining.
Paul Karbon was cautioned for an overzealous challenge and after the Rams took the free kick quickly Referee Shepard brandished a red card for Wilkinson?s seemingly innocuous tackle on Matt Toogood.
With the Demons faithful anxiously adjusting their watches, their anxiety turned into anguish at the death after Shepard pointed to the spot in the last kick of the game.
Macarthur coach Paul Carter felt his team was good value for a point but lamented their lack of composure in the final third.
?We had a number of chances to put Blacktown City Demons to bed but weren?t good enough to take them,? he said.
?We had two clear cut chances to score and created more openings but just weren?t clinical enough.
?At this level if you have clear openings you have to take them and that is why we find ourselves midtable.?
His opposite Ken Schembri was happy with the effort from the Demons but felt the penalty call was dubious to say the least.
?We worked hard all week and to lose two points in the last kick of the game is incredibly frustrating,? he said.
?In terms of the penalty you will have to ask the referee himself why he gave it.
?I actually thought it was a foul on Matt Pressello and when the boys told me it was a penalty I couldn?t believe it.
?In three games that is two penalties we have conceded so you have to ask what is going on.
?I was happy with the effort shown overall and we can use the performance as a platform to build on in the coming weeks.?
Blacktown City Demons 1 (Bruno Salas 45 ‘)
Macarthur Rams 1 (Renato Jelen 94′)
Blacktown City Demons: 1.Ivan Necevski, 6.Ken Chun, 3.Paul Karbon, 12.Brendan Maroney, 2.Matt Pressello, 11.Nick Rouco (Leo Carle 76?), 9.Bruno Salas, 25.Jordan Simpson (Adam Biddle 60?), 7.Tyler Simpson (Ryan Walsh 71?), 19.Brian Vanega, 4.Daniel Wilkinson
Subs Not Used: 20.Matt Nemes, 8.Chris Bedzo
Macarthur Rams: 1.Brody Crane, 4.Jason Lewis (Andrew Keady 30?), 5.Michael Brown, 6.David Gardiner, 7.Matt Toogood, 11.Sam Mort (Hugo Coronel 45?), 16.Steven Baveas, 14.Daniel McCann, 17.Adam Wither, 19.Paul Crisp, 21.Renato Jelen
Subs Not Used: 3.Adel El Jamal, 20.Matthew Kabarian
Referee: Ryan Shepard
Assistants: N.Tragoustis & G.Askham
Cautions: Tyler Simpson (BCD) 19?, Daniel Wilkinson (BCD) 36?, Matt Toogood (MR) 67?, Paul Karbon (BCD) 79?, Bruno Salas (BCD) 90?
Red card: Daniel Wilkinson (BCD) 80?
Crowd: 500 (Approx)
3- Bruno Salas (BCD)
2- Ivan Necevski (BCD)
1- Matt Toogood (MR)
-By Andrew Hurrell