Fuel-tank probe rekindles old issue

The placement of fuel tanks on passenger vehicles has changed over the past three decades, and for good reason.

Automakers gradually have repositioned the tank to an area in front of the rear axle, generally below the rear passenger seat. Statistically speaking, the tank in that location is less vulnerable in a high-speed, rear-end crash than in the previous location--between the rear bumper and axle.

Fiery crashes of the Ford Pinto and Mercury Bobcat in the 1970s prompted automakers to rethink how to protect the gasoline tank.

Now fuel tanks are in the news again. Last month the National Highway Traffic Safety Administration began a preliminary investigation of 3.1 million 1993-2004 Jeep Grand Cherokees to determine whether the plastic tank, check valve and fuel filler hose fail in rear-end crashes and rollovers, releasing gasoline that catches fire.

These days, all automakers place the tank within the frame, ahead of the rear axle. The only exceptions are the Ford Crown Victoria, Mercury Grand Marquis and Lincoln Town Car.

But those 1993-2004 Grand Cherokees have the old configuration: The fuel tank is between the rear bumper and axle.

"While I think the dangers of aft placement are exaggerated, its just good, normal practice to place it inboard on all cars and trucks," says a former Detroit 3 executive who asked not to be identified.

Bad timing for Jeep

NHTSA says that since 1992, 44 Grand Cherokee crashes and 55 deaths have been reported in which fire was listed as the most harmful factor. Of those, 10 crashes and 13 deaths were linked to rear-end crashes. NHTSA will determine whether a recall is necessary, but the agency said a preliminary review did not find the vehicles to be over-represented for post-crash fires.

All this happens at an inauspicious time for Chrysler Group, which has just rolled out a redesigned Grand Cherokee. Not only does the new version have the gas tank inboard--that is, within the frame--but so did the version it replaces.

Still, the new investigation is a headache for Chrysler. The 2011 Grand Cherokee is a crucial vehicle on its road to recovery. Chrysler has been running an extensive multimedia ad campaign for the vehicle and doesn't plan to stop.

Chrysler spokesman Michael Palese says the automaker is cooperating with NHTSA. He says the investigation is not a recall. The 1993-2004 Jeep Grand Cherokee meets or exceeds all federal safety standards and has an excellent safety record, Palese says.

If NHTSA determines a recall is necessary, it will tell Chrysler to create a fix for the problem.

The investigation was prompted by a petition from the nonprofit Center for Auto Safety, founded by Ralph Nader. Clarence Ditlow, the center's executive director, says the safety issues differ between the 1993-98 version of the Grand Cherokee and the 1999-2004 edition. But he says both generations have one thing in common: "A lot of the fatal fire crashes [involve] low-profile vehicles."

Two of the vehicles, for example, a Ford Taurus and Toyota Celica, wedged underneath the Grand Cherokee, lifted the vehicle up and moved the gasoline tank forward and upward, he says. The Grand Cherokee's fuel tank hangs partly below the rear fascia.

For 1993-98 models, Ditlow says, Chrysler cut a hole in the vehicle's frame rail and placed the fuel filler hose through the hole. The filler hose extends from the gasoline cap to a check valve.

The valve prevents gasoline from escaping from the fuel tank. When fuel is added to the tank, the pressure of the flowing gasoline opens the valve to allow gasoline into the tank. When refueling is completed, the valve automatically closes.

In a crash conducted by the Center for Auto Safety, Ditlow says, "that hole pinches the hose and pulls it out. The hose is not long enough."

With the force of the accident, "the check valve came out with the filler hose" releasing gasoline, he says.

"It clearly had a structural weakness," Ditlow says. "I know of no other vehicle that has ever had a filler hose go through a frame rail."

The Grand Cherokees under investigation all had plastic fuel tanks. Ditlow says the tanks involved in the fatal crashes melted.

An unprotected hose

Manouchehr Kambakhsh, vice president of technology at fuel systems supplier TI Automotive, says about 85 percent of the tanks used by North American automakers are made of plastic.

A steel tank is less expensive. But, Kambakhsh says, there is no difference in safety between the two tanks.

"Safety has nothing to do with the material," he says. "The structure and integrity of the plastic and metal tanks" are equal.

But it does depend on what measures an automaker takes to protect the tank and filler hose.

Regarding the Grand Cherokee, Ditlow says, "Putting a reinforcement bracket along the top of the frame rail would take care of the issue of the frame rail being too weak" due to the hole.

"You need a protective shield underneath [the frame rail], and Chrysler has a shield that is pretty good." The shield had been offered as an option, he says.

A skid plate positioned under the tank also might be needed for protection, he says.

When the next generation of the Grand Cherokee--1999-2004 models--was developed, the frame was re-engineered, and the frame rail did not have a hole. Chrysler relocated the hose, curving it around and under the frame rail.

But nothing protects the hose from being damaged or potentially pulled from the check valve for the tank, Ditlow says.

"We are going to crash-test that [generation] in about a month," he says.

When the 2005 and later Grand Cherokees were engineered, the tank was relocated under the rear seat. The tank for the redesigned 2011 Grand Cherokee is also under the rear seat.

Ditlow says: "There were a couple of good engineering decisions that were made as a result of the DaimlerChrysler merger. The 2005 Grand Cherokee was one of them."

By Rick Kranz- Automotive News