Got a 2009 or 2010 Volkswagen Golf or Jetta with the TDI clean diesel engine? Or an Audi A3 TDI? Ever had the engine stall unexpectedly?

If so, the National Highway Traffic Safety Administration might like to hear from you.

The NHTSA announced Friday on its website that it is upgrading an investigation into fuel-pump failures on VW's TDI-engine vehicles to what it calls an engineering analysis. In many cases, the results of that analysis may be used in a recall to fix a defect that has been identified and shown to affect a disproportionate number of vehicles.

2010 Volkswagen Jetta Sportwagen TDI

2010 Volkswagen Jetta Sportwagen TDI

One accident and 160 complaints were reported to the agency around the issue of diesel stalling or unexpected loss of power. It received 52 of the complaints directly, and the rest through Volkswagen.

In about half the cases, the engines stalled unexpectedly and would not subsequently restart, which is particularly dangerous when it occurs at highway speeds.

2010 Audi A3 TDI

2010 Audi A3 TDI

The cause is thought to be failure of the pumps that provide fuel to the high-pressure injectors that squirt a measured amount of diesel fuel into the combustion chamber.

These pumps have to be much sturdier than fuel pumps for gasoline engines, because the compression ratio of modern diesel engines can be roughly twice as high as that of gasoline engines.

If those pumps fail, shards of metal or other materials can enter fuel lines and other parts of the fuel system, blocking and contaminating the entire system.

2010 Audi A3 TDI

2010 Audi A3 TDI

Like other makers, Volkswagen re-engineered its diesel engines to meet new emissions standards that went into effect for the 2009 model year.

A total of 97,300 vehicles were sold among those three models over two years, the agency said.

Volkswagen said it is cooperating fully with the NHTSA investigation and analysis.



Follow GreenCarReports on Facebook and Twitter.