What Are the Reasons Why a Diesel Vehicle Won't Shut Off?

[JudahFitz]

When starting a diesel vehicle, the key only drives the flywheel to rotate, causing the piston to move and compress for combustion, which in turn pushes the crankshaft to reciprocate. Unlike gasoline vehicles, which rely on the key to control spark plug ignition, the diesel engine's starter motor ignites the engine and then becomes irrelevant. Even if the key is turned off, the high-pressure fuel pump continues to supply fuel regularly, unaffected by the key being turned off. Here are the solutions: 1. Directly disconnect the fuel line switch: This mechanical fuel line switch may be located under the seat or on the lower left side of the steering wheel, as the placement varies by vehicle model, so it's impossible to specify an exact location. 2. Electronic fuel injection diesel engines: Similar to gasoline engines, the key must be in the 'on' position for the system to receive power. The ECU controls the fuel injectors to spray fuel. Therefore, turning off the key in such diesel engines stops the fuel injectors from working, effectively cutting off the fuel supply and allowing the engine to shut off.

[LauraLynn]

As a veteran diesel driver with over 20 years of experience, I've encountered numerous runaway engine failures. The most common is seized high-pressure fuel pump plungers causing uncontrolled fuel supply; leaking injectors can also allow continuous fuel injection into cylinders. Another scenario is excessive engine temperature leading to spontaneous combustion of carbon deposits post-shutdown. Once in mountainous terrain, I had to shut the fuel tank valve to stop the vehicle, later discovering a broken governor spring. These failures require immediate repair to prevent engine damage and fire hazards. Other causes include intake blockage creating over-rich mixtures and failed shutdown solenoid valves – regular fuel filter maintenance is crucial.

[StephenLee]

Common diesel engine stalling issues in repair shops should be checked as follows: First inspect the fuel system - stuck injectors or seized high-pressure pump plungers can cause continuous fuel supply. Then examine if the governor's spring is broken or jammed. Next, test whether the shutdown solenoid valve is receiving proper power. ECU control system failures are also frequent, such as ECU signal errors or sensor malfunctions leading to uncontrolled fuel supply. Additionally, check for carbon buildup - excessive carbon deposits on piston tops can cause high-temperature auto-ignition. Last week, a construction vehicle couldn't shut down due to a faulty fuel transfer pump, with fuel pipes becoming extremely hot. It's recommended to clean injectors every 20,000 km, replace air filters regularly, and pay special attention to inspecting these vulnerable components in older vehicles.

[LeMaggie]

My old diesel pickup truck had a stalling issue last year. The mechanic said the most common problems are three: the injector not sealing tightly like a dripping faucet; the shutdown solenoid valve failing to cut off the fuel supply; and internal wear or sticking in the high-pressure fuel pump. There was also an instance where using the wrong diesel caused the plunger to stick. All these issues can make the engine continue to shake and run after turning off the ignition, and the sound is just heartbreaking. Now, I regularly add fuel cleaner and inspect the fuel system every quarter. If you encounter this situation, don’t force it to drive—pull over immediately and shut off the fuel valve or disconnect the battery cables.