Cummins says it has “paused” work on its 14.9-liter natural gas engine because of “uncertainty” of the demand for such power plants amid the expense of fueling stations and on-board tanks.

It will re-evaluate the engine’s future later this year, the company said in a statement on Wednesday.

The ISX15 G, announced in 2012, is a spark-ignition design similar to that of the smaller 11.9-liter ISX12 G that went into production last year.

With up to 400 horsepower, the “12G” has begun serving heavy truck customers who want to use inexpensive natural gas, but is not considered strong enough for heavy tractor-trailers operating in the mountainous West.

In October, Westport Innovations, a Cummins partner in development of natural gas technology, discontinued its 15L dual-fuel, diesel-natural gas engine due to low sales. The Cummins view of market potential for its larger engine seems to jibe with the Westport experience.

“As a result of market timing uncertainty, Cummins has paused the development of the ISX15 G natural gas engine,” the company said in the statement.  “While we believe natural gas power will continue to grow in the North American truck market, the timing of the adoption of natural gas in long-haul fleets preferring 15-liter engines is uncertain.  

“We believe the adoption of natural gas in long-haul fleets will be paced by a variety of factors beyond the engine, and include fuel tank technology and public fueling infrastructure,” Cummins said.

Natural gas fuel tanks account for more than half the steep cost of equipping a truck to burn the otherwise less expensive fuel. And while fueling stations are springing up along major shipping lanes across the U.S., they are still too few in number to support widespread long-haul operations that the 15G would see, observers have noted.

“Cummins remains committed to the natural gas market,” the company’s statement said. “Heavy-duty fleets desiring natural gas power currently have the option of the Cummins Westport ISX12 G, which is available in a wide range of heavy-duty truck OEMs.”

Aftermarket natural gas conversion systems are an alternative to buying new natural gas power, and are available for installation on diesels in late-model trucks as well as in newly assembled glider kits. The aftermarket systems are dual-fuel, and run engines on both gas and diesel fuel.