What happens when the fuel supply is cut off to the engine? Basically I'm wondering if the car just shuts off the injectors and is there a minimum fuel pressure that our cars needs to keep running? I see many have a problem with there cars just dying out of no where and I was wondering if fuel might be a cause. Is there still spark even though there is no fuel coming through the fuel rails.

 

When there is no fuel pressure, there is no flow from the injectors. Engine stops running without fuel. There is still spark, but without fuel there is nothing for the spark to ignite.

If you lose partial fuel pressure, you will get reduced flow from the injectors, and your engine will run lean. If you are lucky, the O2 sensors will pick up the lean condition, telling the PCM to keep increasing pulse width to make up for the low fuel pressure. But eventually, the PCM will reach its limits to control the fuel flow through the injectors, and you will get a "lean" code set. If you are not lucky, the engine will detonate due to running lean, and do some serious damage.

The PCM does not know the fuel pressure, so it can not react directly to loss of fuel pressure. It has to rely on feedback from the O2 sensors. If you're running an open loop tune, it doesn't even have that feedback.