Fuel Systems Flashcards
7 cards from real ASE 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 flashcards as text
On most gasoline direct injection (GDI) engines, what drives the high-pressure fuel pump?
Answer: A lobe on the camshaft
GDI high-pressure pumps are usually mechanical piston pumps driven by a camshaft lobe.
What is the typical operating rail pressure range for a gasoline direct injection system?
Answer: 500–2,900 psi
GDI rail pressure typically runs from a few hundred psi up to roughly 2,900 psi (about 200 bar).
Why are GDI engines prone to carbon buildup on the intake valves?
Answer: Fuel no longer washes over the back of the intake valves
Fuel is sprayed straight into the cylinder, so nothing cleans the oil vapor deposits off the intake valves.
Before opening the high-pressure side of a GDI fuel system, what should the technician do?
Answer: Disable the low-pressure pump and confirm rail pressure has bled down with a scan tool
GDI rails can hold dangerous pressure, so the pressure must be confirmed near zero before opening.
A vehicle sets P0442 (EVAP small leak). What is the most effective tool for finding the leak?
Answer: Smoke machine
A smoke machine fills the sealed EVAP system so the smoke shows where it is leaking.
Which symptom is most likely caused by an EVAP purge valve stuck open?
Answer: Rough idle or hard starting right after refueling
An open purge valve pulls heavy fuel vapor into the intake, especially after refueling, which makes the mixture too rich.
During an EVAP system leak-test monitor, how is the canister vent valve normally commanded?
Answer: Closed, to seal the system
The vent valve closes to seal the system so the PCM can watch for pressure or vacuum decay.