Fuel Systems & Fuel Delivery Flashcards
7 cards from real NAPA practice questions. Tap to flip, then mark Knew It or Still Learning — missed cards come back until you master them.
Read the first 7 Fuel Systems & Fuel Delivery flashcards as text
During a fuel pressure test, what does rapid pressure drop immediately after the pump shuts off indicate?
Answer: A faulty fuel pressure regulator or leaking fuel injectors
Rapid pressure bleed-down after pump shutoff indicates fuel is leaking back through a failed pressure regulator or injectors that are not sealing properly.
What instrument is used to measure fuel pump volume output during a flow test?
Answer: Graduated cylinder timed flow test
A graduated cylinder is used to capture fuel pumped over a timed interval so the volume can be compared against the manufacturer's flow specification.
Which condition is most likely to cause a persistently rich air-fuel mixture?
Answer: A leaking fuel injector that drips when commanded closed
A leaking injector allows fuel to enter the cylinder even when it should be closed, adding excess fuel and creating a rich condition.
What is the correct method for testing a fuel injector's electrical coil?
Answer: Measure resistance across the injector terminals with an ohmmeter
An ohmmeter measures injector coil resistance; values outside the manufacturer's specification indicate an open or shorted injector winding.
What is the most common cause of in-tank electric fuel pump failure?
Answer: Habitually running the fuel tank at very low levels, reducing pump cooling
In-tank pumps are cooled by the surrounding fuel; consistently running low deprives the pump of cooling and causes it to overheat and fail prematurely.
What does evaluating an injector's spray pattern reveal about its condition?
Answer: Whether the injector atomizes fuel into a proper mist or streams and dribbles
Spray pattern testing shows if an injector produces a uniform cone-shaped mist; a streaking or dribbling pattern indicates internal wear, clogging, or a damaged pintle.
What is the purpose of a fuel system check valve (one-way valve)?
Answer: To maintain residual pressure in the fuel lines after the pump shuts off
The check valve prevents fuel from draining back to the tank after shutdown, maintaining residual pressure that allows for quicker restarts and helps prevent hot soak vapor lock.