Running engine (diesel) with the ignition turned off

[Robert Wilson]

Somehow I motored about fifteen minutes with the ignition turned off. What potential damage?
Twin cylinder 13HP Kubota

It may have been my error (distracted....), with three wee things and four adults in the cockpit playing with/touching things they ought not to.
Everything seems fine and the engine started instantly when leaving the anchorage a few minutes later.
What does the team think?

TIA

 

[VicS]

Somehow I motored about fifteen minutes with the ignition turned off. What potential damage?
Twin cylinder 13HP Kubota

It may have been my error (distracted....), with three wee things and four adults in the cockpit playing with/touching things they ought not to.
Everything seems fine and the engine started instantly when leaving the anchorage a few minutes later.
What does the team think?

TIA

No problem

It just meant that for 15 minutes your instrumentation and alarms were not working.

Your stop system may not have worked either if the engine has an electrical stop solenoid operated by a stop button.

 

[coveman]

As far as I am aware you shouldn't have any problem. Basic old diesel tractors run fine without the ignition being switched on - your only drawback is you wont be charging the battery.

 

[Kelpie]

I remember being told that it can damage the alternator, as it will be spinning but not able to send the power anywhere. Could be a load of b*llocks though, would be interesting to know if there's any truth in it.

 

[VicS]

As far as I am aware you shouldn't have any problem. Basic old diesel tractors run fine without the ignition being switched on - your only drawback is you wont be charging the battery.

I remember being told that it can damage the alternator, as it will be spinning but not able to send the power anywhere. Could be a load of b*llocks though, would be interesting to know if there's any truth in it.

The alternator output does not go through the ignition switch.

It would have continued to charge the battery ( provided it was up to speed before the ignition was switched off) without causing any damage to the alternator. Possibly a different kettle of fish if the battery isolator had been opened

 

[JumbleDuck]

Somehow I motored about fifteen minutes with the ignition turned off. What potential damage?
Twin cylinder 13HP Kubota

It depends a bit on how it happened. If you have a 1-2-Both switch and the ignition went off because someone turned that to "Off" you might, possibly have damaged the alternator. However, that really only applies to old alternators, as newer ones have protection against damage from turning when disconnected. I once ran my 1GM10 for several hours with the 1-2-Both at "Off" (because it was dark in the cupboard under the sink and I though I was turning it to "Both") and there was no damage at all.

Otherwise you'll have done no harm at all. If you have an electric engine stop it might be worth finding out why it didn't do anything. When the panel fuse on my Nanni 14 (Kubota) blew this summer, the engine stopped immediate. As, nearly, did my heart.

 

[Robert Wilson]

Good news folks. Thank you.
I think what must have happened was that after a few minutes of starting and running, the ignition either was switched off or I hadn't turned it fully on and it "fell back" to off.

No electric "off" and the battery switch was to "both".

Breath another day!! :encouragement:

 

[sarabande]

Just a long chance, Robert. Have you checked the crankcase oil level after all your work on the donk earlier this summer? If the level is too high, some engines can draw the oil into the induction side and keep running. Always indicated by lots of smoke and a 'runaway' feeling. I think yours is safe, though.

 

[VicS]

It depends a bit on how it happened. If you have a 1-2-Both switch and the ignition went off because someone turned that to "Off" you might, possibly have damaged the alternator. However, that really only applies to old alternators, as newer ones have protection against damage from turning when disconnected. I once ran my 1GM10 for several hours with the 1-2-Both at "Off" (because it was dark in the cupboard under the sink and I though I was turning it to "Both") and there was no damage at all.

Otherwise you'll have done no harm at all. If you have an electric engine stop it might be worth finding out why it didn't do anything. When the panel fuse on my Nanni 14 (Kubota) blew this summer, the engine stopped immediate. As, nearly, did my heart.

Your engine must have a fuel solenoid that is energised to run. If the power to it is cut the engine stops ........Just as happens in a diesel engine car when the ignition is switched off.

Most small boat marine diesel engines have a stop solenoid ( if not a mechanical stop ) which is energised to stop the engine . That is why the key has to be held in the stop position or the button pressed until the engine comes to a standstill.

 

[Robert Wilson]

Just a long chance, Robert. Have you checked the crankcase oil level after all your work on the donk earlier this summer? If the level is too high, some engines can draw the oil into the induction side and keep running. Always indicated by lots of smoke and a 'runaway' feeling. I think yours is safe, though.

Hmm, I did notice the oil level was slightly high after replacing the injectors, but I checked the "smoke n running" and all seems fine.
Thank you.
What with no wind, too much wind and the injector problems it hasn't been the best of sailing seasons, but I have had some thrilling evening sails.
All looks to be sorted now, fingers crossed, and I'm relieved this latest hiccup has been given the thumbs up from the Forum.

Plenty more weeks of this season, so I hope to get some good cruising .

I hope all of you are enjoying good sailing.

Slainte mhar

 

[JumbleDuck]

Your engine must have a fuel solenoid that is energised to run. If the power to it is cut the engine stops ........Just as happens in a diesel engine car when the ignition is switched off.

Most small boat marine diesel engines have a stop solenoid ( if not a mechanical stop ) which is energised to stop the engine . That is why the key has to be held in the stop position or the button pressed until the engine comes to a standstill.

I think it's an energised-to-stop solenoid which runs via relay from a timer on the on/off switch (which at my request is a button, not a key). Evidence:

(a) Last year the "stop" fuse blew (Nanni, it seems, show traditional French optimism about wiring) and turning off the panel didn't stop the engine

(b) This year the main panel fuse blew and the engine died at once

(c) The on/off switch has a relay behind it which goes "clunk" about five seconds after power is turned off.

Here's the wiring diagram. Panel supply is the 10A fuse; stop supply is the lower 15A one.

It seems unnecessarily complicated, and is one of the reasons I really wish I had put in another 1GM10 and not the blasted Nanni. At a saving of £2.5 k or so ...



PS Only the glow-plug fuse hasn't blown yet, and I have a spare ready for that.

 

[johnalison]

I have always sailed under the impression that turning off the ignition while motoring was absolutely verboten, so I too am relieved to see that this is not necessarily the case. I have always been in the habit of using the phrase "kill the engine" instead "turn off the engine" when asking my wife to perform the deed in order to alert her to what I am asking.

 

[Robert Wilson]

I have always sailed under the impression that turning off the ignition while motoring was absolutely verboten, so I too am relieved to see that this is not necessarily the case. I have always been in the habit of using the phrase "kill the engine" instead "turn off the engine" when asking my wife to perform the deed in order to alert her to what I am asking.

My thoughts, entirely :encouragement:

 

[PaulRainbow]

Most, if not all, stop solenoids on boats are normally in the run position, with power being required to stop the engine. You don't want to be stranded at sea because a flat battery has shut the engine down. I had a feeling it might be in some regs or other, but not 100% certain.

As for killing the alternator, turning the "ignition" switch off will not harm the alternator, it will keep charging. It's common practice to connect the alternator charging cable to the starter solenoid cable (that goes to the battery positive), in which case if you turn the switch off, the battery doesn't get charged and the alternator could be damaged.

If a VSR is fitted, it makes no difference as the battery cables don't need altering.

If i diode or similar split charge device is fitted (Victron ArgoFET or other makers similar device) is fitted it depends how this was wired. Most will be connected directly to the battery positive or to the battery terminals of the isolator switches, in which case it won't harm the alternator if the switch is turned off. If the installer connected to the load terminals of the isolator, then, unless you turn off both the engine and the domestic isolators it still won't harm the alternator.

In short, to damage the alternator you need two things :

1) An alternator with no protection against being removed from the batteries

and

2) You need to isolate the alternator from all of the batteries.

 

[prv]

In short, to damage the alternator you need two things :

1) An alternator with no protection against being removed from the batteries

and

2) You need to isolate the alternator from all of the batteries.

All true, but the most likely reason for anyone to be fiddling with battery switches under way at all is because they have a 1-2-both switch. Such switches provide an easy single-action way to do exactly point 2), isolate the alternator from all batteries - all you have to do is a quarter turn the wrong way (single battery to "off" instead of single battery to "both") or do the turn you intended but not starting from where you thought you were (meant to go from "both" to a single battery, actually was already on that battery and went to "off").

So it comes down to point 1), and of course the older boats with old manual electrics are more likely to also have older alternators...

Pete

 

[scotyount]

As far as I am aware you shouldn't have any problem. Basic old diesel tractors run fine without the ignition being switched on - your only drawback is you wont be charging the battery.

Diesel engines don't have ignitions. If they did they wouldn't be diesels....

 

[RichardS]

Diesel engines don't have ignitions. If they did they wouldn't be diesels....

Mine are both diesels and both have an ignition key .... although the two keys are identical and the same as every other 3YM.

Richard

 

[VicS]

Diesel engines don't have ignitions. If they did they wouldn't be diesels....

We know , we know. but the key switch is generally refereed to as the "ignition switch" . and the key refered to as the "ignition key" Even Richard, who knows perfectly well that diesels dont have ignition systems calls the keys ignition keys

 

[alan_d]

Mine are both diesels and both have an ignition key .... although the two keys are identical and the same as every other 3YM.

Richard

The point being made is that although many of us have a key-switch for the engine, it is technically an "ignition" switch only on a petrol engine. Petrol engines have an ignition system comprising spark plugs and something to provide a high voltage to them at the right time, which is turned on and off by an ignition switch. Diesel engines, which do not have electrical ignition, cannot have an ignition switch, although I have never heard anybody call the analogous device on a diesel engine the "electrical ancillaries switch".

 

[coveman]

Diesel engines don't have ignitions. If they did they wouldn't be diesels....

Not in the strict sense of the word no, but diesels engines still ignite their fuel albeit by mechanical compression rather than by spark plugs etc. This is known as adiabatic compression causing a rise in the temperature of the gases in the cylinder which causes the fuel to ignite. I have never heard the key for a diesel being called anything other than the "ignition" key.