Phoenix ? An idled gasoline pipeline that is causing fuel shortages throughout Phoenix failed one of two tests needed to reopen it, the owner of the line said Wednesday.

However, the pipeline was expected to be back in operation and running at full capacity by the weekend, said Rick Rainey, a spokesman for Kinder Morgan Energy Partners of Houston.

The pipeline provides a third of the metropolitan area’s gasoline and the shutdown has caused days of shortages and long lines at gas stations in this sprawling city with relatively little mass transportation.

Kinder Morgan said a test using high-pressure water in one segment of the pipeline was going well and was expected to be completed Wednesday, but a second segment failed the test near Tucson.

The failed section was being repaired and a new test will be needed, company officials said. The failure was located near the spot where the pipeline burst on July 30, Rainey said. The pipeline was shut down Aug. 8 after other safety concerns surfaced.

Meanwhile, in a move aimed at easing the shortage, the federal Environmental Protection Agency on Wednesday granted Gov. Janet Napolitano’s request that the metropolitan area be allowed to use conventional rather than cleaner-burning fuel until the gas supply stabilizes. The waiver expires Sept. 19.

Since 1997, the federal government has required gas stations in the Phoenix metropolitan area to use gasoline blended with ethanol or another additive to combat high ozone levels.

There are no gasoline refineries in Arizona, so fuel must be delivered through two pipelines operated by Kinder Morgan — the closed one, which runs from Texas, and a second from California, which is still working.

Kim Pappas-Miller, a spokeswoman for AAA Arizona, said one gas station near downtown Phoenix was charging $3.89 a gallon; $2-a-gallon prices were common elsewhere in the city.