I discovered a curiosity with my car. I just wondered if others have noticed the same. With the inertia switch disconnecting I always assumed there would be zero fuel pressure as it disables the pump. But after and oil change and a cranking to get pressure I noticed 1 bar (got a guage fitted for some tests). It also attempted to fire several times.

Anyone got any ideas how this happens? My only thought was that there must be some sort of pumping action with vacuum and injectors.

After a bit of discussion with some engineery types, the theory is that it it is not unlike a bubble jet printer. The vacuum sucks fuel through the injectors and then they slam shut. The inertia of the fuel in the fuel line creates pressures and the fuel pump valve holds it. The process probably aided by vapour, or air, in the system.

So if you car fires with the fuel pump disabled, the chances are something similar is happening.