Suddenly losing your car's engine power is no doubt a harrowing experience, especially if you're on the highway. But that's what some BMW owners are saying has happened to them. After what Toyota (TM) has gone through this year with massive safety recalls, if such a problem is as widespread as it seems, BMW may already be late in getting in front of the problem. The luxury carmaker says it has not heard of cases where the engine lost power on the highway.

The first I heard of this potential problem was Monday, July 19, when I received an email from BMW owner Allison Mangot, who lives in the New York City area. She contacted me after reading a DailyFinance article I had written about Toyota. When I spoke with Mangot, she was clearly upset about the incident she experienced. In May 2010, she was driving her 2008 BMW 535xi wagon, and she says the engine simply stopped working.

She was still upset when we spoke because the day before, July 18, her husband was driving his 2009 BMW 335xi convertible on the Cross Bronx Expressway on a congested Sunday afternoon when New Yorkers were returning from weekend trips, and his car's engine stopped while he was in the left lane driving 55 mph. Fortunately for all involved, he was able to keep the car rolling long enough to pull it off the road without any injury.

It "Put My Family's Life in Danger"

It turns out Mangot and her husband aren't the only ones to claim problems with these cars. I've checked the National Highway Traffic Safety Administration's (NHTSA) Office of Defects Investigation (ODI) website, which lists complaints from the public about different vehicles. I counted 38 nearly identical complaints regarding BMW 335 and 535 models from 2007 to 2010, most of which mentioned problems with the "high-pressure fuel pump" (HPFP) used in these models' engines. Here are three typical ones, with excerpts from the actual consumer complaints (the ODI complaint number is in parentheses):

Engine suddenly shut off. Lost power steering on freeway while going 65 MPH (10304620).
High pressure fuel pump malfunctioned while merging on a freeway on-ramp, resulting in a near rear-end collision as the vehicle suddenly slowed due to the malfunction (10217997).
Malfunctioned coming off of the freeway in Los Angeles resulting in complete loss of power. This has put me and my family's life in danger (10243352).
A failed fuel pump could easily cause an engine to stop running or to run erratically at best. After all, if there's a problem with getting fuel into the engine's cylinders, the motor will be starved, leading it to suffer reduced power, erratic running or potentially stalling out completely. According to NHTSA's safercar.gov site, BMW has not initiated a recall nor is NHTSA investigating this problem now.

Beware of "Drivability Symptoms"

However, BMW is aware of fuel pump problems because it has issued so-called Technical Service Bulletins to its service departments for the BMW 335i. Here are links to two such bulletins -- one for vehicles made June through October 2006 and another for vehicles made in Jan. 2007. There may be more. The TSBs are carefully worded to suggest that the failed HPFPs cause "drivability symptoms."

And in May 2010, BMW issued a TSB that extended the HPFP warranty from "4 years or 50,000 miles to 10 years or 120,000 miles, whichever come first." But this does not mean BMW owners are satisfied -- after all, as of July 23, more than 360 of them have signed an online petition entitled "BMW No More Fuel Pump Failures."

Arthur C. Wheaton, director of the Western N.Y. Labor and Environmental Programs at Cornell University's School of Industrial and Labor Relations, says the existence of these TSBs indicates that BMW has communicated with NHTSA and "is in full compliance with the law."

Overwhelmed by Toyota Recalls?

However, Clarence Ditmar, director of the Center for Auto Safety, says with nearly 40 fuel pump problems on the BMW 335 and 535 series already reported to NHTSA, he would expect the agency to conduct an investigation. He thinks it may not have started one because it's so overwhelmed with Toyota's recalls.

And it's not like NHTSA doesn't know about the problem. On April 28, 2008, it launched an investigation into the BMW 335i HPFPs -- the failure of which caused problems, including complete engine stall on the highway. The details of this investigation are available on NHTSA's safercar.gov site. To view them, key in the NHTSA Action Number PE08032 and then click the document search button.

This site documents the 2008 investigation. For example, NHTSA obtained from BMW a list of 718 HPFP complaints from 335i owners (note: this is an extremely large download of a Microsoft Excel spreadsheet) between Oct. 18, 2006, and May 19, 2008. NHTSA closed the investigation on Aug. 15, 2008, because the engines stalled in only 4% of the complaints.

NHTSA decided at that time that "further investigation of this matter would not be an efficient allocation of agency resources." However, it added: "The closing of this investigation does not constitute a finding by NHTSA that a safety-related defect does not exist."

Is It a "Known Safety Defect"?

Wheaton says he thinks the recent BMW complaints aren't yet significant enough to get NHTSA's attention because there have been no reports of death or injury. However, he also says that if BMW doesn't have a complete fix for the problem, then it would be a so-called Known Safety Defect -- requiring BMW to stop selling all vehicles affected. This outcome would be far more costly than a recall.

Nevertheless, as long as there has been no "serious risk to life or limb," Wheaton doesn't think BMW will feel any sense of urgency. If NHTSA does end up investigating the problem and requires BMW to recall the affected vehicles, he thinks the carmaker might decide to "send a message that 'We value our customers, so we'll voluntarily go beyond what NHTSA required to make sure all affected vehicles are up to snuff.'" But that remains to be seen.

NHTSA's site describes how it decides on vehicle recalls. Here's an excerpt: "Generally, a safety defect is defined as a problem that exists in a motor vehicle or item of motor vehicle equipment that:

Poses a risk to motor vehicle safety, and
May exist in a group of vehicles of the same design or manufacture, or items of equipment of the same type and manufacture."
If a car suddenly loses power on the highway -- or on any busy road -- and the cars behind it aren't paying attention, they could easily hit that decelerating vehicle. This sounds like a safety risk. And the complaints with the BMW 335 and 535 suggest that the problem exists in a group of vehicles.

NHTSA declined to comment beyond what's on its website. BMW's David Buchko said that fuel pump malfunctions might cause long 'crank times' to start the engine or cause the engine to go into 'limp mode' -- in which the car slows down but does not stop so the driver can safely pull over to the side of the road. However, Buchko said that he had not heard of any cases where the engine stalled because of the fuel pump so he could not comment on that.

It's a blessing that nobody has been seriously hurt so far from this problem. But even if only 4% of the cars with faulty fuel pumps actually stall because of the malfunction, it seems it's just a matter of time before someone in that small group becomes truly unlucky.