The GMC engines are two stroke and use a roots blower to provide scavenging pressure. As the blowers are lubricated by engine oil pressure if a shaft seal fails it injects lube under normal operating pressure into the incoming air stream. If you shut off the fuel under this condition the engine won't stop; if you shut off the air it will.
Didn't the engine have a spring loaded "damper" in the intake when you got it?
yes, it does.
Ignoramus31413 wrote in rec.crafts.metalworking on Tue, 21 Jun 2011 23:38:18 -0500:
That should be an easy fix. I think you will soon have a great machine.
Ignoramus3171 wrote in rec.crafts.metalworking on Wed, 22 Jun 2011 07:11:36 -0500:
FYI: A CO2 fire extinguisher can stop a runaway engine. A little pricey, but sometimes things can go real bad, real fast. If you have one, you might want to have it handy.
That is the normal emergency shutdown device. But as someone wrote it is a bad practice to use them as a "normal" shutdown device. If you have some strange wiring around the engine and a solenoid on the inlet damper you probably have the remnants of an automatic shut down system. They usually have sensors for high water temperature, low oil pressure and over RPM.
There is no injector pump on a Detroit Diesel :-)
True, but there is a feul pump, and the injectors use fuel for lubrication. Hard for either of them to run dry. Also killing a Detroit with a board, or simular object over the air inlet is not recommended as it can ruin the oil seals in the blower. Iggy, you need to get a manual and figure out how to set the governor, and injector racks, but be carefull, I have seen guys set the governor on Detroit diesels, and if done wrong they will go full throttle and the only way to stop them is to shut of the fuel, or choke them like you are doing, neither was is a good thing to do often. with the Detroit3-53 to kill the engine the throttle needs to be brought back past idle and this will stop the injectors from injecting fuel into the engine. The fuel ramp in the injector goes to zero fuel. I have set the governors on this style of Detroit myself, but it was thirty years ago!
Greg O
Yep, fixed it, runs great now.
i
Yep, everything is exactly as you describe. I took the bad injector out, fixed it, reassembled and now this engine runs like a champ.
ijohn B. wrote in rec.crafts.metalworking on Thu, 23 Jun 2011 09:51:04 +0700:
I didn't know that. How does it work?
There is a fuel pump that delivers a lot of fuel to injectors.
The injectors take a small part of that and, when they are depressed by special arms, shoot a little bit of fuel into the cylinders. In other words, injectors are the pumps.
i
No. but there IS a "control rack".Which should allow total fuel cut-off to all injectors at once.
If the injectors are not stuck, that is.
iIgnoramus1214 wrote in rec.crafts.metalworking on Thu, 23 Jun 2011 17:28:16 -0500:
Wow, never heard about that kind before. I guess I learned something new today. Ok, so how does the throttle work? Vary the fuel pressure? Or the duration of the spray pulse?
How is the spray pulse timed? A lobe(s) on the camshaft?
Exactly what I meant by "should"
There is no throttle, but there is a governor. The governor exerts force on the rack, which in turns pulls those little things that stick out of the injectors, and regulate the amount of fuel injected.
i
There is a fuel pump that supplies fuel to the individual injectors through a passage in the head. A camshaft pushes down a plunger, or piston on each injector at the apropriate time, a few degrees before the piston reaches top dead cnter of it's stroke. The governor controls the amount of fuel injected by variing the amout each injector delivers into the engine. Each injector has a small rack and pinion setup and the governor moves this rack back and forth. Internal to each injector is a ramp of sorts that is controlled by the rack and pinion that effectively closes off more or less of the plunger bore to change the amount of fuel. To shut the engine down the rack is retracted and no fuel is injected.
Greg O
A drilling rig? No compound?
Sure, see
The compound connects the main engines to the rest of the rig, and allows the use of several engines to power the rig.
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