All three lanes eastbound were shut while firefighters tackled the blaze just before junction three, at Wesham.
Firefighters were called to the scene at around 6.50pm on Wednesday. Police also attended.
At 7.45pm, a Lancashire Police spokesman said traffic was moving slowly following the incident.
He added: “The motorway is no longer closed but it is heavy with traffic and there may be some standing traffic.
“There were no injuries and the vehicle has been dealt with and is on the hard shoulder.”
It is not clear how the fire started.
Lengthy delays have been reported by motorists heading towards Blackpool as a result of the incident.
At around 7.15pm, Lancashire Police’s roads policing unit tweeted: “Full closure M55 westbound immediately prior to J3 at the moment: vehicle fire. No injuries.”