Insane Hydraulics
Bold and audacious blog about fluid power
This is a short add-on to the post Can You Stop the Monster. It pursues, basically, two purposes - one - to present yet another amusing example of how unstoppable the mechanically injected diesel engines can be, and two - to provide proof to the universal fact that in absolutely any situation, despite all training, planning, and preparation, something at some point will go wrong!
Several years ago I participated in the restoration of an outdated Toro 500 - an underground front loader, powered by a true engineering marvel - a V-twelve Deutz. These air-cooled diesel engines, equipped with mechanically governed fuel injection, have earned the fame of being bulletproof survival experts, capable of dishing out countless work hours under all sorts of environmental ill-treatments. I was told that due to the environmental restrictions the mine wasn't allowed to buy such machines anymore, but could still run the already existing ones. This particular loader served as an "organ donor" for its "siblings" for about two years before a decision was made to "resurrect it" as a piece of auxiliary equipment. After the reassembly, the hydraulic brakes wouldn't work, and so I was asked to assist.
The malfunction turned out to be bad connections. Luckily, the hydraulic schematic was there, and the brake problem was solved quickly. While making the necessary adjustments and verifying the rest of the hydraulic system, I had to turn the engine on and off several times. Since I had already had my share of, let's say, "peculiar" experiences with unstoppable diesels, one of the first things I checked was the engine shut down system, which was working flawlessly, and was activated by a small spring-loaded hydraulic cylinder. To stop the engine a valve injected oil into the cylinder, and the cylinder would pull or push on something, and the engine would stop. I am not sure whether it was a decompressor or a fuel valve, but it doesn't matter.
Everything was working fine, the engine was starting and stopping as required, and my job was almost done. As I was talking to the shop mechanic, I pointed out a pilot pressure filter that looked like it had never been replaced. The all helping fellow immediately took the filter element out of the housing and rushed to the warehouse to get a replacement. The housing, naturally, remained open. Very pleased with myself (the job had gone incredibly well) I deiced to make one last pressure check...
Just like I'd been doing it for the last couple of hours, I installed a pressure gauge, went to the cabin, and turned the ignition key... When the key was about half way - a thought flashed through my mind - "An open filter in the pilot line means no pilot pressure! How the hell are you going to stop the engine, you moron?!" - at that time my brain commanded the fingers to stop turning the key, but it was already too late - the tenth of a second the ignition contacts touched each other was enough for the stupid but very well adjusted diesel engine to start turning... By instinct, I pushed the stop button already knowing that there would be no pilot pressure to operate the stopping mechanism (which, by the way, was well hidden in the middle of the engine). I climbed the three-meter high frame in under a second and saw exactly what I was expecting to see - the engine going pa-pa-pa-pa, and the stream of hydraulic oil coming out of the disassembled pressure filter and poring all over the loader and onto the shop floor...
The hours were late, and since the shop mechanic ran to the warehouse I was alone with the mindless critter, which was pouring gallons of hydraulic oil on the floor. Calling for help was not an option since I couldn't possibly outscream the twelve jugs, so I had to find a way to stop it, and stop it fast (but not for good, though...) I looked around and saw a piece of rubber band on the floor, which seemed to be large enough to cover the air intake, so I went for it and spread the band directly over the huge inlet - I could swear it was airtight, but the freaking engine wouldn't stop!!! I was looking at it and wasn't believing my eyes! How in hell it was possible?!!! The diesel was clearly choking, spitting out clouds of black and white smoke from the exhaust, but it was not stopping! In another desperate attempt, I managed to twist the fuel hose in my hand, and after half a minute of doing ta-pum-pum-ta-pum-chaka-chaka it finally seized kicking. When I jumped down, doing my best to avoid the large oil puddle on the floor, I finally looked at the engine with "seeing eyes" and noticed that the V-twelve had two air intakes - one for each six cylinders - so to smother it I had to close both of them... which I didn't.
To conclude - once again, mechanically injected diesel engines can be a pickle to stop once they've started turning, so before turning one on, make sure the shutdown system works and that you have studied other stopping options. Oh yes, one more thing - in case you decide to smother an engine - don't forget that it can have more than one air intake!!!