Yanmar 4JH3 Just Keeps Running . . . and Running

[Hudsonsailor]

Hi
In case you haven't tried this. This a normal problem when some one turns the key switch to the OFF position before activating the shut off button until you hear the audible signal
while engine is still running turn key to Run position, (not Start) and press shut off button

[Cadence]

Originally Posted by Hudsonsailor

Hi
In case you haven't tried this. This a normal problem when some one turns the key switch to the OFF position before activating the shut off button until you hear the audible signal
while engine is still running turn key to Run position, (not Start) and press shut off button

Brilliant! I'll bet you cured the problem.

[Peregrine1983]

Originally Posted by jls095

Just cover the air intake with a hard cover book or piece of wood in a pinch. No need to shut off the fuel supply. It'll die immediately.

+1 for that. A big book or a solid piece of wood works. Don't use something that will break and get sucked in.

[pcmm]

Originally Posted by jls095

Just cover the air intake with a hard cover book or piece of wood in a pinch. No need to shut off the fuel supply. It'll die immediately.

Why make the problem harder than it needs to be, there is a lever on the body of the injection pump that the solenoid is connected to, just move it with your finger. its really easy to move.

[ScottRhodes13]

One thing to keep in mind when manually activating the stop plunger ... If you don't have power to activate the plunger, you may not have power to restart the engine. So make sure you're somewhere you can sit for awhile while you fix the problem.

[Statistical]

Seriously it is a good idea to be familar how to manually kill your diesel engine. The two options are shut off the fuel or shut off the air. Practicing both AT THE DOCK before you need it will improve confidence.

Even the cable style fuel shutoff can break or slip. Good to know where the lever at the other end of that cable is located. It takes all of 5 seconds to kill the engine ...if you know where it is. Same thing with solenoid. I have never seen a fuel shutoff solenoid that can't also be manually actuated but exactly how varies by engine model.

If you ever get diesel in the crankcase in a hot engine the only way to shut it off will be killing the air. The hot engine oil will vaporize the diesel and the air intake will be pulling in a mix of fuel and air. Google some videos of runaway diesels. So shutting the engine off with a hardback book or wooden board over the air intake is good practice. If you have never done it before you likely aren't going to figure it out the first time when your diesel is redlining at 4,000 rpms ready to shake itself apart.

[pnw2022]

Originally Posted by captlloyd

Keep this idea in mind for a run-away diesel ! A run-away can keep running even after the fuel supply is shut off. It can start sucking the oil out of the pan and use the oil for fuel. You can see a bunch of run-aways on YouTube. Scary.

+1 on this again. Separate issue, but it can happen.
Hopefully never, but it is good to know where the air intake is, and have at least some kind of rudimentary plan about what to do.

Meanwhile for the original use case, the shutoff valve at my tank is easily accessible so that is my plan there should it be needed.

[Statistical]

Originally Posted by pnw2022

Meanwhile for the original use case, the shutoff valve at my tank is easily accessible so that is my plan there should it be needed.

Keep in mind fuel shutoff at the tank if relatively slow. The lift pump will draw fuel until suction pressure reaches its limit before the engine dies which can be quite a while.

I just changed the fuel filter on my 3MG30F. The only shutoff upstream of the filter is at the tank. Shut it off. Replaced filter, bleed the system, and let it run as a test. 20 minutes later is starts stuggling and when I reduced the throttle it dies. Only then did I remember the fuel shutoff. Opened it and it started and ran fine.

Long story short the engine may run 10-30 minutes after fuel shutoff at the tank depending on filter capacity, load, and engine.

The fuel shutoff (aka engine top) lever at the engine (cable driven or solenoid driven) is instantaneous. It forced the govenor to drop to zero fuel which pull the injector pump to completely closed.