Shannon Taylor (22), of Port Chalmers, was in the back yard of a friend's house in Port Chalmers, working underneath a Ford Falcon station wagon with the ignition on.
He said he had incorrectly wired the fuel pump, which caused a spark, ignited fumes and created a ''flame ball'' at the rear of the car and he had caught fire.
''I rolled out and I ran up and down the path trying to put myself out.''
The screams of his friend's girlfriend alerted two people to act and ''save my life''.
After hearing the screams, Port Chalmers Pool supervisor Lyndon Johnston emptied a fire extinguisher on the station wagon and a neighbour, Tracey Loach, put Mr Taylor in a cold shower.
He had severe burns and nerve damage to the left side of his body but the cold shower stopped more skin melting.
''It could have been a lot worse. I could have lost a lot more skin.''
The second-degree burns had left no skin on his left arm and hand, which could be permanently damaged and require skin grafts, he said.
''I can barely sit up or walk. I can't do anything.''
In hospital, he was woken by nightmares of ''flashbacks of flames''.
He had fallen out of bed three times yesterday attempting to walk and lacked the energy to attend a meeting with his pregnant partner and midwife.
Mr Taylor hoped to be discharged from hospital for the birth of his second child in 10 weeks.
He was philosophical about the ''freak accident''.
''I would have done things differently but you can't turn back time and what's happened has happened and there will be a lot of recovery.''
