DIY Guide on Inhibiting and Repairing Diesel Engine Runaway

May 2015

When the car’s diesel engine starts eating its own diesel, the condition is called diesel engine runaway. It is a rare condition in which extra fuel is extracted by the engine from unintended sources, putting the car on higher RPM and speeds. It creates emergency situations with engine self-surging, even if the driver is not controlling the accelerator. In such a case, the driver must pull the car to the roadside and check the engine for technical solutions.

Common Causes of Diesel Engine Runaway

Breakage in internal fuel pipe, breakage of oil seals in turbocharged engines, excessive oil mist created by crankcase in highly worn engines, external hydrocarbon activity in air intake systems, leaked gas interfering with engine air intake, and vapor accumulation in air intake filters are some common causes of diesel engine runaway.

Technical Steps to Stop a Diesel Engine Runaway

The driver must try to safely control brakes, power and steering of the car. Hitting your car with something to stop the engine will result in engine burn and smoke. The easiest way is to apply brakes to your runaway TDI engine and turn OFF the ignition. Just after half a second, press the accelerator and brakes at the same time.
Turning off the ignition will stop the fuel supply to the runaway engine. If you have an Mk3 TDI engine, then the anti shudder valves will cut the fuel supply and stop solenoid. If you have Tk4 TDI engine, then ask a helper to turn the ignition ON without starting the engine. Turn off the solenoid if it is still working.
When you turn off the ignition, the electronic intake flap will also close, turning off the air flow. Choke the engine manually if it has not immediately shut off.
You can also turn off the air intake by covering the air intake system or plugging it off.
If the engine is still working even after turning off the ignition, then spray Carbon Dioxide in the air with a fire extinguisher.
The engine can be manually stopped with high gear transmissions at 4, 5 and 6 gears and applying full parking brakes.
Although rare, but diesel engine runaway is an emergency situation which may take someone’s life. In order to avoid such emergency situations, regular inspection of diesel engines must be done by a reputed automotive technician.