ALBANY, N.Y. — Angry about the price of gas? Just imagine paying for gas you don't get.

Some alert consumers have noticed it over the years: A pump that seems to hesitate a second when the lever is squeezed. Anywhere from 2 to 6 cents tick off before the rush of gasoline starts. That's what happens with a common, hard to diagnose and mostly ignored problem with the "check valve," which is supposed to make sure gas flows at the same time the price meter starts.

But even if your gas pump works, it can still be off as much as $5 for every fill-up. Tests by local regulators allow a pump to charge as much as 6 cents more than the gas delivered in a five-gallon test, but there can be wild fluctuations. Federal regulators said they had heard of swings of as much as 30 to 40 cents per gallon.

Don't blame the gas guys. Even consumer advocates say retailers may be losing as often as consumers and no one appears able to rig the meters. But the small "check valve" at the end of the multibillion dollar industry just wears out, and often goes unnoticed for months.

Regulators' records show short staffing, particularly for financially struggling counties that try to inspect pumps every six months, but too often don't even meet the one-year requirement in states like New York.

Federal standards require all gas pumps to start pumping gas as soon as the price meter starts, said Ken Butcher of the National Institute of Standards of Technology, part of the U.S. Commerce Department.

Bob Wolfram knew something was wrong when the pump he used in Davenport, Iowa, showed he put two more gallons of gas into his tank than the tank holds.

"I was low, but it wasn't negative," said Wolfram, a 54-year-old engineer.

He reported it to a consumer Web site then took it to the government regulators, who acted promptly. But even then, the test showed the pump was only off a quart.

"I just kind of said, 'What will they do next?' " Wolfram said.