The family of a Sydney plumber stabbed more than 30 times before his unit was set on fire still hold out hope the unsolved homicide will be resolved.

Firefighters found Paul Munt's body with stab wounds across his torso and neck in his Auburn unit in Sydney's west in March 2009.

The 48 year old also had bruising to his face.

Despite a detailed and exhaustive police investigation, no one has been arrested over the suspected murder.

Deputy State Coroner Carmel Forbes referred the case to the unsolved homicide team on Monday after hearing it was still unclear why Mr Munt was stabbed to death or who was behind the crime.

"It's perfectly obvious that Paul Munt was stabbed to death in his flat," Ms Forbes told an inquest at Glebe Coroner's Court.

"But one thing we don't know is how all that happened."

Detective Sergeant Joseph Maree told the court police believe accelerant was used to set Mr Munt's unit on fire.

"It was deliberately started I believe to destroy any forensic evidence that the offender or offenders may have left behind," he said.

Police found a bottle of engine coolant at the unit.

Det Sgt Maree believes someone who knew Mr Munt was involved.

"I believe the person or persons that were involved know Paul and I think that's how they gained entry to the premises," Det Sgt Maree said.

The homicide detective believes there was an argument in Mr Munt's unit before Mr Munt was assaulted and stabbed.

The court heard Mr Munt was most likely dead when the fire started.

While there were suspects in the investigation, no clear motive for Mr Hunt's death in his housing commission unit had been established.

Det Sgt Maree believes there are people, possibly connected to those behind Mr Munt's death, who may one day come forward.

Mr Munt's brother, Steve Munt, is also holding out hope.

"We hope to get an answer one day and that it's resolved," he said outside court.

Steve said his younger brother's death always played on his mind but "over time things always seem to get easier".