How do you stop this?

Cover the intake completely to starve it of air

Diesel runaway... Suffocate it by cutting off the air intake supply

A fire extinguisher will stop it. Every truck man should drive with one in case of a runaway engine. The engine is running on its own engine oil instead of diesel at this point. Cutting the power won’t stop it. Cutting the fuel won’t stop it. You have to stop air.

Thats called "diesel engine runaway", and the only way to stop it is covering the air intake. If you cant cut the air supply, clear the area. Super dangerous. That thing will explode.

Cut air

Disconnect the battery if possible

@aaaarrrrrggh Rag in the intake. Runaway diesel

Pull the ignition fuse

Air intake choke it

Pull the battery, turn the ignition off or remove the master fuse.

Cut the fuel

Fly the banner and disarm the battery

Put it in gear and lift clutch .. cover the intake . Stall the engine

Just turn the truck off

Put it in high gear and make the engine stall itself

Remove battery terminal Cut ignition.. no spark.. no run