Injector Stiction

Canonical Definition

Sticking or sluggish movement of an injector needle or plunger due to deposits, lacquer formation, water contamination, biological growth, or particle abrasion within the precision clearances of a fuel injector. In HPCR injectors, stiction causes misfiring, uneven fuel delivery across cylinders, excessive smoke, high-pressure pump wear, and engine power loss. Stiction can be temporary (wash-out possible) or permanent (mechanical scoring of plunger and barrel surfaces). Water above 200 ppm in diesel fuel is a primary trigger for injector lacquer and stiction.

Engineering Context

Injector stiction diagnostics use injection correction factor data from the engine ECU — a high positive correction for a cylinder indicates low injector delivery (stiction), a negative correction indicates excessive delivery (leakage past a scored plunger). Fuel system cleaning procedures using high-concentration injector cleaner additives can resolve early-stage deposits, but mechanical scoring from particle contamination requires injector replacement.

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