1999 Pontiac Grand Am Case Study Fuels and Ignition

Fuels: Possible initiating fuel sources included power steering fluid, coolant and gasoline. There was no evidence of any breaches though all these fluids were in the area of fire origin as indicated by the burn pattern. Witness statements suggest power steering failure just prior to observed smoke and while the engine was still running. Power steering lines and fittings were in close proximity to the center of the burn pattern and the shielded exhaust manifold. While polymeric fuels were secondarily involved, the fire scenario suggests that they were not involved in fire initiation. Based on the incident description, burn pattern and location of potential fuels, power steering fluid was determined to be the most likely initiating fuel.

Passenger side rear of engine compartment; bulkhead is toward top in photo. Power steering lines are shown by arrows.

Ignition : Power steering fluid most likely autoignited on the shielded exhaust manifold. It showed dark discoloration on its underside, toward the passenger side in the area of power steering lines. Electrical wires were not a likely ignition source because they were not located in the area identified as the fire origin. Given the description of power steering failure, which was most likely a pre-fire event, it is unlikely that ignition was caused by electrical system malfunction because this would require two simultaneous failures.