Motorcycle Crash and Burn: Fuel Filler Cap Analysis By Curtis Beloy, P.E.

A man on a sport-touring motorcycle was involved in a single vehicle crash while riding on a country road. Immediately following the crash, flames began to engulf the motorcycle and the man sustained injuries from the fire.  A claim was brought against the motorcycle manufacturer alleging the fuel filler cap on the fuel tank was defective, resulting in leaked fuel and the post-crash fire.  According to the Plaintiff’s testimony, there had been prior occasions where he attempted to close the fuel cap after a fuel stop, only to have the cap come open shortly thereafter.  He further testified that at the time of the subject crash, he saw fuel spilling out of the cap as his motorcycle was falling to the ground.  Since the ignition key of the motorcycle is used to access the fuel cap, the claims included that the fuel cap design should incorporate a safety mechanism which prevents removal of the key unless the fuel cap is properly latched.

The fuel tank and fuel filler cap of the accident motorcycle were made primarily of plastic; therefore, they were almost completely destroyed in the vehicle fire.  Upon inspection of the charred vehicle remains, structural metal parts in the immediate area of the fuel tank displayed collision damage, raising suspicion that the fuel tank was damaged during the crash.  Crash-related damage to the fuel tank was one possible explanation for a fuel leak.

Safety Engineering Associates (a Crane Engineering company) purchased an exemplar model of the subject motorcycle and performed an analysis of the fuel cap design and function.  When used properly, the fuel cap assembly latched securely and gave clear feedback to the operator by means of a tactile and audible “click” due to the latch springing into place.  The operator could also observe when the cap is properly closed, as it becomes flush with the top surface of the tank.  Laboratory test data and video demonstrations documented the ease and simplicity of the system when used properly.

The Plaintiff testified in a deposition that his typical process while completing a fuel stop included closing the cap, turning the key, and then removing the key.  These actions are not consistent with the manufacturer’s instructions, which clearly specified to firmly push the cap closed and then pull the key straight out.  The unnecessary and improper action of turning the key prior to removal could retract the latch and place the cap in a semi-latched, intermediate state that is prone to opening.  This improper usage of the fuel filler cap lock system is consistent with his past experiences with the fuel cap opening after a fuel stop.

A survey was conducted of the various fuel cap designs on the new and pre-owned inventories of the local motorcycle dealerships.  Of the motorcycles that required a key to open the fuel cap, there was nearly an even split between fuel caps that required the key to be in to close the fuel cap and those that didn’t.  For the fuel caps that required the key to close the latch, the vast majority of which would allow the key to be removed while the cap was not fully latched.  Only a small percentage overall had a design where the key could not be removed from the fuel cap until the cap was completely closed with the latch secured.  Therefore, the Plaintiff’s motorcycle was equipped with a fuel cap and lock system similar to what is available on the vast majority of motorcycles on the roads today.

The motorcycle dealer’s records included receipts showing that the plaintiff had purchased an aftermarket tank-mounted bag, which mounts via an adapter to the fuel filler cap retaining ring.  The same model adapter and tank bag were purchased and fitted to an exemplar motorcycle.  With the tank bag in place, it was found that the fuel filler cap was obscured from view.  This proved that plaintiff’s testimony that he saw fuel spill out of the cap was impossible.

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