Force a Diesel Engine to Stop

Diesel Troubleshooting Article

Why in the world would you need to know how to shut down a diesel? An owner recently had his ignition switch go bad. The key wouldn't turn back to the off position. He couldn't shut off the engine. A pure mechanical diesel engine unlike a gas engine does not need an electrical spark for ignition. On a gas engine all you have to do is take away the electricity and the engine can't run. A diesel uses the heat of compression to ignite the fuel so removing the electricity from a diesel may not stop it from running.

There are of course, exceptions to this. All modern diesel engines use some electrical devices too operate. Almost all diesels have an electrically operated fuel shutoff solenoid and electric fuel lift pumps. Others like the turbo diesels use an electronic injection pump. As long as these engines are getting air, fuel and electricity they will continue to run. Cutting off the electricity to these engines should stop them. One exception would be a N/A diesel with a malfunctioning fuel shutoff valve.

Never disconnect the battery from a running truck. You may ruin the alternator. Disconnecting the battery won't stop the flow of power because the alternator is still spinning generating power.

All the Hummer diesels have electric lift pumps that suck the fuel out of the tank through a filter and deliver it at low pressure to the high pressure injection pump. These lift pumps have had problems where they just stop pumping. As long as the fuel line doesn't have any leaks the engine will continue to run because the high pressure injection pump has enough pulling power to suck fuel from the tank on it's own. That's why disconnecting or disabling the fuel lift pump will not shut down the engine.

The hmmwv's and the Hummer N/A (naturally aspirated) diesels have mechanical injection pumps. All the turbo diesels have electronic injection pumps with computer controlled engines. Both pumps have electrical fuel cutoff solenoids. This is how the engine is shutdown when you turn the key off. If the ignition key doesn't work and the solenoids are working you should be able to shut down a diesel by closing the solenoid and shutting off the fuel supply to the engine. You have to find the electrical connector to the solenoid and either pull it off or cut the wires.

On the electronically controlled trucks you can fool the computer into shutting down the engine by pulling the oil pressure sender on the top of the engine. The computer will think you lost oil pressure and activate the fuel cutoff. On a Pre-'99 TD truck pull fuse 6B - PCM / Ign Power / Brake Switch. On a '99 to '03 truck pull the equivalent fuse. This will cut the power to the electronically controlled injection pump and cause the engine to stop.

If the fuel shutoff solenoid is broken and won't close you should unplug the fuel lift pump, go to the fuel filter housing and open the air bleeder (black cap on the top) or unscrew the top of the filter housing. This will let air bleed into the fuel system and stop the engine. If you do stop the engine in this manner you will have to purge the air to get it started again.

The engine can be shut down by restricting the fuel return at the injection pump.

Since the engine needs air to run choking the air supply will also kill the engine. You can remove the mushroom cap air intake and put a piece of wood over the top to stop the air. Be aware that a running diesel engine is a very high powered air compressor. It will pull a considerable amount of vacuum at the inlet when you choke off it's air supply. Don't use anything that could break apart and get sucked through the air filter and into the engine.

Another possibility is to block off the exhaust. I think you will find that this is nearly impossible to do since the pressure created by the running engine will be very hard to overcome.

It was also suggested that you try a CO-2 fire extinguisher sprayed into the intake.