The Worthington Cup winners face the Portuguese giants walking a tightrope following the 0-0 in the first leg, knowing that they must push forward and win the game ever wary of the dangers of the away goal.
Anfield has seen many great European nights over the years and the manager is hoping that the crowd can re-create that atmosphere to rally his troops.
"This is going to be a big night for the club and for the fans. We are all in this together and we will need them tonight," said Houllier.
"They are a part of this club. Ever since Shankly's era there has been a great relationship between the club and its supporters and if we go through tonight we will go through with them.
"We have a tradition of having passionate, noisy fans and we will need that against Porto. Those fans can give us a lot of confidence and impetus in this game.
"They have been fantastic to aid the team in games like the Crystal Palace semi-final, and then the Roma home game when we were under so much pressure.
"If we go through it has to be with the fans behind us because the club is a whole, you know how important the fans are to the players.
Nick Barmby is ruled out for Liverpool while Emile Heskey and Stephane Henchoz will have late fitness tests just before the game.
Finnish international Jari Litmanen could start his first game for a month after recovering from the calf injury he sustained during the FA Cup game against Manchester City.
Houllier could do with Litmanen's vast European experience gained with Ajax and Barcelona to see his side home.
Fernando Santos will be glad to have Russian playmaker Dmitri Alenitchev from suspension as his creative flair was sorely missed last week.
Captain Jorge Costa was injured in the first leg and will be unable to play, while there are injury doubts over goalkeeper Sergei Ovchinnikov and midfielder Carlos Paredes.
Porto take a dismal away record to Merseyside, having lost six of their last seven away from the Estadio das Antas, but Houllier is aware that they will be bringing the experience of seven Champions League campaigns in eight seasons to Anfield.
"It is not an easy game to handle because we have to score. At 0-0 you know that means extra time and penalties in the end, and we don't want that," said Houllier.
"We have to show shrewdness from a tactical point of view."
"We need to be very careful because with no away goals we have to score and make sure we keep a clean sheet.
"They are a very good side, very experienced. The game is not comfortable from our position.
"This will be a big game for big players, and we know they have an attacking style which they don't change when they play away.
Liverpool are playing their 20th Cup tie of a season that could lead to an incredible cup treble, but Fernando Santos is confident that his side can win, despite their poor away record.
"Roma winning at Anfield showed it is possible but we knew that already," said Santos.
"Anfield doesn't intimidate us. We are an experienced team just like Liverpool. We are used to challenges and this is just another game.
"The draw wasn't what we wanted at home. We wanted to bring a lead here but we know a draw will be good for us now.
"Liverpool are not a typical British team and play a more compact game. They didn't attack that much in Porto. Tuesday they will have to attack more."
Betting: Liverpool 1/2, Porto 9/2, Draw 13/5 click here for details.
