Why do engine stalls due to air bubbles in fuel circuit ?

Common Rail Injection systems, or for that matter most diesel fuel engines, use high pressure to deliver a very fine mist (almost a vapor) so it burns evenly and increases efficiency. The injector opens for a fraction of a second and the fuel is sprayed in. read more

If there is air in the line, It gets compressed and the pump can't build up the pressure quickly enough between injections (gases compress very easily as opposed to liquids, which are relatively in-compressible), so when the injector opens, it doesn't get much fuel through and the engine stalls. read more

Cold stalling problems are the most common because the engine needs a richer fuel mixture to maintain idle speed until it warms up. Intermittent cold stalling problems are almost always fuel-related. On older engines with carburetors, cold stalling (and hard starting) is most often due to an automatic choke that is sticking, misadjusted or broken. read more

Your engine can stall if it is being starved of fuel. If the fuel pump isn’t supplying enough fuel to the engine, or if the air/fuel mixture is too lean, the engine doesn’t produce enough combustion in the power cycle to stay running, and will stall. A faulty fuel pump or incorrect timing can cause this. read more