This is a great question! I can't speak to the role of the Honolulu Fire Department for the rest of the war, but civilian firemen did respond to the attack on December 7. Some were killed, and nine received Purple Hearts (a very unusual honor for civilians).

The first shots at Pearl Harbor likely came when Japanese planes arrived over Wheeler Field, a fighter airstrip near the center of Oahu, around 7:55 a.m. Other Japanese aircraft arrived over Pearl Harbor itself and attacked surrounding airfields minutes later. One of these was Hickam Field, just east of Pearl Harbor but west of Honolulu. Hickam was the largest airbase on the island and home to the Army's long-range bombers.

The first call to the Honolulu FD arrived at Engine 6 at 8:06 a.m., almost immediately after a shift change at 8:00. The men at Engine 6 had apparently heard explosions and were watching smoke rise to the west, waiting for the call. There was an arrangement between the military firefighters and the civilians that they would provide assistance to one another if needed, so the Honolulu firemen were expecting to be called. It took about 12 minutes for the six men of Engine 6 to reach Hickam, so it was close to 8:20 when they arrived. Two other units from the Honolulu FD (Engines 1 and 4) also arrived, putting 18 civilian firemen at Hickam Field.

They found that the military fire station at Hickam had been attacked and a fire truck that had left the station had been strafed, with its driver dead at the wheel. The Honolulu firemen were basically on their own. Making matters worse, the water main to Hickam Field had been destroyed in a bomb blast, which meant the fire hydrants weren't working. The bomb crater around the water main was filling with water and the firemen began the process of pumping out the water there to fight the fires when they noticed Japanese planes returning for another attack run. The firemen scattered for cover, but three were killed and several others were wounded. Their equipment had also been damaged by shrapnel, machine gun bullets and bomb blasts. When the firemen emerged after that attack, they tended to their wounded and did what they could with the hoses and equipment that were still working.

The second wave of Japanese aircraft arrived around 9:00, scattering the firemen once again. When those planes left, the firemen did what they could to jerry-rig their equipment and fight the fires at Hickam Field. Most accounts recall that the firemen used bar soap and toilet paper to patch holes in the radiators of their fire engines.

All off-duty civilian firemen were called back to their stations via radio announcements around 8:30, in the middle of the first wave. A small number of trucks were comandeered by the fire department so they would have enough vehicles to respond to whatever calls came in. The Honlulu FD responded to 39 total calls on December 7, though not all came in because of the Japanese. The massive amount of anti-aircraft fire thrown into the air by the American army and navy included several shells that failed to explode in mid-air and fell back to earth. Dozens of Hawaiian civilians were killed in the attack, and while there were instances of Japanese planes that strafed civilian vehicles or bombs that killed civilians, most of the civilian casualties came as a result of errant American ordinance that exploded in Honolulu or elsewhere. One call for the fire department was to respond to an explosion at an elementary school where civilians had been sheltering when a shell exploded there, killing three people.

The immediate response would have been a slog. The military handled the damage done at the navy base and many other facilities, but civilian firemen still had to respond to downed electrical wires, secondary fires, and other calls around the island. Every fireman was on duty until Tuesday morning, December 9. This would have been a tense time also, with false rumors of a Japanese invasion and worries about additional attacks.

Notably, six men of the Honolulu Fire Department who were wounded on December 7 received Purple Hearts in 1944. The three civilian firemen who were killed that day received Purple Hearts decades later in a separate ceremony. It has always been unusual for civilians to receive the Purple Heart, and civilians are no longer eligible for the award (there is now a separate honor for them). The nine Purple Hearts awarded to the members of the Honolulu Fire Department are the only ones ever bestowed on civilian firefighters.