FAA Aviation Mechanic Powerplant (AMP)Fuel, Induction and LubricationMedium
During a ground run, a mechanic observes that engine oil pressure remains excessively high even after the engine reaches normal operating temperature. The mechanic suspects the oil pressure relief valve is stuck. In which position would this cause the observed symptom?
- AAdjusted with a weaker spring than specified
- BStuck closed, preventing excess oil from bypassing back to the pump inlet or sump
- CStuck open, allowing continuous bypass of oil to the sump
- DRemoved entirely from the oil pump housing
Show answer & explanationAnswer & explanation
Correct answer: B. Stuck closed, preventing excess oil from bypassing back to the pump inlet or sump
The oil pressure relief valve is spring-loaded to open and bypass excess oil back to the pump inlet or sump once system pressure exceeds a set value, limiting maximum oil pressure. If the valve is stuck closed, no oil can bypass, so pressure continues to rise above normal limits.
Why the other options are wrong
- A. A weaker spring would cause the valve to open too easily, lowering pressure, not raising it.
- C. A valve stuck open would bypass too much oil, causing low pressure, not high.
- D. A missing valve would also cause uncontrolled high pressure, but the mechanic found the valve stuck, not absent.
Oil Pressure Relief Valve
A spring-loaded valve in the lubrication system that opens when oil pressure exceeds a preset limit, bypassing excess oil back to the pump inlet or sump to protect the system from overpressure.
- Located near the oil pump discharge
- Opens at a calibrated spring pressure setting
- Stuck closed causes high pressure; stuck open causes low pressure
Memory trick: Closed valve traps oil in, pressure climbs high.