CNG bus issues likely due to low fuel grade

But no definitive cause for troubles discovered

By Mark Reaman

The effort to get the first local bus to run on compressed natural gas (CNG) into the RTA (Gunnison Valley Regional Transportation Authority) fleet continues to stall. Work is being done by the RTA, the county, Alpine Express, the CNG supplier (Trillium) and the engine manufacturer (Cummins) to figure out what is causing the issues that are keeping the CNG bus off the highway.

JP Frymoyer of Alpine Express, which manages the RTA shuttle fleet, told the RTA board at the September 1 meeting that the bus came of out Reno and ran fine getting to the valley. That was in early May. When the bus arrived, Alpine Express had to wait until the Gunnison CNG fueling station was finished and then the bus was filled with fuel from the new station. Frymoyer said it ran fine for a while but had some minor issues with loss of power.

“We are finding out now that there were probably some misfires with the first fuel we put in from here,” Frymoyer said. “There were more misfires once we refueled the next time with the Gunnison fuel.”

The CNG was tested by Atmos Energy and Xcel Energy and found to be within correct specifications. Frymoyer said Cummins personnel came in and did some tweaks to the bus that they hoped would solve the problem. It didn’t.

“We defueled the bus and used some fuel that was brought over by RFTA [Roaring Fork Transportation Authority] and the bus ran great,” Frymoyer relayed. “Cummins was monitoring the bus and there were no misfires while running on the RFTA fuel. We filled it with Gunnison fuel and there were problems pretty quickly. The signs are pointing to the fuel. Our on-road tests indicate we have a fuel issue.”

Frymoyer said four fuel test samples were sent out to independent labs for analysis. “This is a high performance engine and the thought is maybe it needs a higher grade fuel, comparing it to a car that might need 91 octane gasoline as opposed to 85,” he said. “I am not sure what will happen but it will turn out okay. Everyone is working well together, Trillium and Cummins.”

RTA executive director Scott Truex agreed. “We don’t have a definitive answer for the problem yet. Nothing has been verified and we don’t know if it is actually a fuel problem yet,” he said. “We will hopefully get the results from the fuel tests next week. Everyone is working together well to figure out the problem.”

“It is a big bus and we want it in the fleet and running well,” concluded Frymoyer. “It looks really nice, but right now it’s a paperweight.”