What is the likely effect of insufficient valve lift in a fuel injector?

Insufficient valve lift in a fuel injector directly affects the amount of fuel that can be delivered to the combustion chamber. When the valve does not lift sufficiently, it restricts the flow of fuel, resulting in reduced fuel flow to the engine. This decreased flow can lead to an inadequate air-fuel mixture, which can affect engine performance, potentially causing misfires, power loss, and inefficient combustion.

In contrast, the other options presented do not directly correlate with insufficient valve lift. While premature wear of the injector may occur over time due to other factors like poor maintenance or contaminated fuel, it is not an immediate consequence of insufficient valve lift. Increased carbon buildup could be a result of incomplete combustion, but it is more often associated with issues like poor fuel quality or incorrect fuel mixtures rather than directly from insufficient valve lift. Normal operation is not possible when valve lift is insufficient, as it directly impacts the injector's performance.

Therefore, the most accurate outcome of insufficient valve lift is indeed reduced fuel flow, as this condition hampers the injector's ability to pass adequate fuel to the engine.