Engine Wouldn't Quit

[MikeTurner]

Had a strange occurence today and wanted to ask for input.

I have a Perkins 4.108 diesel fitted to a Velvet Drive 1:1 transmission, installed in my Lazyjack 32 schooner. Last month I removed and replaced the water pump">raw water pump and timing cover to repair an oil leak (hole in the timing cover). Since I completed the work the engine has been a bit hard to start with some white smoke when cranking; however the temperatures have dropped here and the engine has no pre-heat or glow plugs so that might account for the hard starting.

Had a hard time starting the engine today in temperature around 50 degrees. Finally got it going after on/off cranking for around 45 seconds total (5 seconds cranking, 5 seconds resting, repeat).

Once started and idling, I went below to check the engine and could smell some electrical overheating. Found smoke coming from the starter. Attempted to stop engine with manual fuel cut-off - no effect, engine still running. Removed bell housing to air filter and stuffed with rags - no effect, engine still running. Tried fuel cut-off again, no effect. Starter now very hot and smoking, I was afraid of fire. As last resort, to cut electrics to starter, moved battery switch from "all" to "off", then after about 5 seconds to house bank (since I've read that running the engine with the switch in the "off" position can damage the alternator). Engine made a squealing sound for about 3 seconds, I thought it was going to seize up; then it began idling again. Tried fuel cut-off and engine stopped.

Subsequent examination of wiring at starter shows suspected short in circuit from key to solenoid. Mechanic friend thinks the solenoid did not disengage and that the starter was still spinning - cause of it heating up, and also cause of engine not quitting when fuel cut off as starter continued to rotate engine.

But, here's my real question - even if this is the case, why did the engine continue to fire once I stuffed the air intake? Shouldn't this have made the engine stop firing? Even if the starter continued to engage, wouldn't I haven noticed a difference between engine idling vs. just being turned by the starter?

I can't figure out how the engine could continue to run once I stuffed the air intake with shop rags. Does this mean it's getting air from somewhere else, and if so, where?

I'm pulling the starter to have it bench checked and will be replacing damaged wiring. But I still have the question about the air, since this would have implications in any run-on situation - I'd always planned to stuff the shop rags into the air intake if I had a run-on, but today that didn't stop the engine. BTW the engine ran at idle speed during the entire incident, did not speed up as I'd read a run-on would.

Appreciate any thoughts anyone has. Hoping there's no damage to the engine beyond the starter and the wiring.

[Cowboy Sailer]

I remember that my engine would not die when I used rags to stop up the air intake but when I jammed a plastic bottle into the intake it then died. I was amazed that the engine could suck that strongly. It must have still gotten air thru the rags.

[hellosailor]

Mike, if a diesel's fuel is cut off and it continues to run, that usually means it is running by sucking lube oil past the rings or some other clever way and combusting that as fuel.

Closing off the air intake should indeed stop that as well, but most diesels have enough compression to simply suck in and ingest anything you can "stuff" into the intake. You'd need a solid plate, something that can't be sucked in, to really stop one.

Which makes it all the more likely that your engine wasn't really "running" but was in fact being turned over by a stuck starter motor.

I'd be surprised if it damaged the engine. Not shocked, just surprised.

[svHyLyte]

Originally Posted by MikeTurner

Had a strange occurence today and wanted to ask for input....

Appreciate any thoughts anyone has. Hoping there's no damage to the engine beyond the starter and the wiring.

Mike--

We had a similar incident when we first got our boat. It turned out that the ignition/starter switch on the panel was defective and after starting the engine, the switch--which is supposed to pop back into the On, from the Start, position, did not and left the Starter engaged. A Starter being spun by the engine becomes a generator and the resulting power out-put burned up our solenoid, the wiring harness, and our starter battery before we were able to stop the damned thing. To stop the engine you have to completely cut off the airflow and rags will not do it. In our case a mechanic at the yard had a hard smooth rubber ball that completely fit the air-cleaner throat and with that he was able to stop the engine. He claimed that I could have just put my hand over the intake without injury but he did not so I don't think I would either. Instead I have obtained a Racquetball ball and keep that threaded on a lanyard near the engine box if the issue ever happens again.

Following the repair, which required the replacement of the Battery, Wiring Harness, Starter Solenoid, Stop Solenoid and ignition switch, I made a routine of squirting a little bit of WD-40 followed by 3-in-1 oil into the ignition key slot on the igntion switch and we've had no more problems.

Further, check your ignition switch. You may not have a glow-plug on your engine but many 4-108's have a "pre-heater" on the air intake. You activate that by turning the key past the Run position but not completely to the Start position. On our boat, holding the key in that position for 10 "Hippopotamuses" (seconds--which seems an eternaty in the event) ensures that the engine will fire on the first or second revolution every time, even with the temps in the 30's (F).

As you reassemble your engine, ensure that your Stop Solenoid was not fried--mine was--without which you'll be back to pulling the stop lever by hand or using the "handball".

FWIW...

[gjordan]

I had read in a diesel repair book to never use rags to try to stop an engine, because they can be sucked far enough into the engine to jam or bend an intake valve. It also said to not try to use your hand. The book recommended using a hard cover book, but the ball idea sounds better. My Perkins 4-154 ran away on me once,(pin hole in the fuel pump diaphram) and I couldnt get it to stop. I could not get the air filter off and had to run back to the helm to keep from hitting rocks. I figured the engine was going to blow. I tacked and the engine went to a smooth normal idle and stopped as soon as I hit the stop button. The high oil level must not reach the cylinder walls on the other tack. The noise was horrible and the smoke was so bad that a man came racing over in a dingy with a fire extinguisher because he thought that we were on fire. After I changed the fuel pump and the oil, I loosened the air filter and left it loose enough to just pull off. Very scary event.____Grant.

[gjordan]

I just remembered a motor yacht that I worked on years ago that had plates on shafts in the intake system(like a carb throttle plate) with external levers to stop the air to the engine in case of a runaway. Woudnt help the electrical problem though.___Grant.