A volunteer firefighter who lit three bushfires and made a swag of hoax triple-zero calls yearned to be on the back of a firetruck, a court has been told.

Jarred William Brewer, 20, sat red-faced and crying in the dock during his pre-sentence hearing on Thursday.

The Melbourne County Court heard the junior CFA firefighter lit three bushfires north of Melbourne and made 16 hoax emergency calls between November 2008 and January this year.

Brewer called triple-zero to report fictitious fires and motor accidents, and hid his identity by removing the SIM card in his mobile phone.

Forensic psychologist Dr Jeffrey Cummins gave evidence that Brewer was of low intelligence and his crimes were a way to big-note himself and boost his self-esteem.

Defence lawyer Sharon Lacy said her client did not commit his crimes out of malice.

She said he simply wanted to be called out by the CFA and had never attended a bushfire.

"Mr Brewer was hoping to be involved in this team of fire fighters that got to put out the fire or at least be on a truck somewhere that attended," she said.

Brewer pleaded guilty to three counts of intentionally causing a bushfire and 16 of improperly using emergency call services.

Chief Crown Prosecutor Gavin Silbert, SC, said Brewer lit two fires at Clonbinane and another at Wallan, north of Melbourne.

He would then make hoax calls to the CFA reporting them, giving a false name and number.

Investigators later matched his fingerprints to ignition items left at one of the scenes.

Receipt records from the local Safeway store - where Brewer bought flammable items - also matched items found at another fire scene.

When police searched his home they found a CFA training manual, sparklers and pyrotechnic material.

Brewer denied, but later admitted, lighting two fires, saying it was for back burning purposes. He couldn't remember about the third.

He told police the hoax calls were for training purposes.

Dr Cummins said Brewer felt he and his fellow CFA members should be getting more experience.

"He felt that he and others in the Darraweit Guim CFA were just not getting the opportunities and experience to utilise and develop their skills," he said.

Brewer had a chronic adjustment disorder in which he suffered anxiety and depression and did not see himself as an arsonist, Dr Cummins said.

He also had trouble understanding the seriousness of his crimes, partly because of his low IQ and mental health problems.

But he said Brewer was not expected to reoffend given his family and friends' reactions to his crimes.

Brewer's lawyer spoke of his previous good character, family support and remorse and said jailing him was not in the community's interest, but the crown requested he be jailed.

Judge Anthony Duckett ordered Brewer, of Darraweit Guim, north of Melbourne, be assessed for a sentence in a youth justice centre.

He will be sentenced at a date to be fixed.