How can you test for a leaking injector without removing it?

• A. Use a stethoscope on the injector to listen.
• B. Disconnect the battery and observe oil pressure.
• C. Check for fuel odor around the injector, signs of leakage when system is pressurized, and perform a pressure hold test by isolating the injector and monitoring rail pressure.
• D. Remove spark plugs to check for wetness.

Answer: (C)

Testing for a leaking injector without removing it relies on two clues: visible signs of fuel leakage and a pressure hold check. Look for fuel odor or wetness around the injector area; that external seepage means fuel is escaping through seals or the injector body. When the system is under pressure, leakage often shows up as droplets or dampness at the injector orifices, indicating a leak while the rail is charged.

To verify more decisively, perform a pressure hold test. With the system pressurized, isolate the injector so it can’t inject fuel and monitor the fuel rail pressure with a gauge. If the rail pressure bleeds off when the injector is isolated, the injector is leaking past its seals or internally. If the pressure stays steady, the injector itself isn’t leaking.

This approach is more reliable for identifying leaks than listening with a stethoscope, which won’t detect flow, or attempting unrelated checks like removing spark plugs or battery changes, which don’t test injector integrity. Safety note: relieve fuel pressure and follow proper procedures when working on the system.