Engine Spontaneously Starts

Hello,

I was working on my portside engine which has a Micro Commander Electronic Control system.

There was two starting stations, one on the bridge and the other in the engine room. I took off the split between the two stations and disconnected the Stern remote station and reconnected the helm harness directly to the control system.

Everything was working well and we thought the issue was where they split the harness.

When I was working on something different, thinking the problem was solved, the engine started on its own. It did it 2 different time which amazed me. The key was in the off position, but the fuse for the Micro Command Center was switched on.


Any ideas why it started.

PS I ended up disconnecting the starter from the battery.

No clue but in such situations, “Put the candle back” usually works!

High Wire said:

No clue but in such situations, “Put the candle back” usually works!

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ditto
You don't need a key to start most diesels. All you have to do is somehow energize the wire running to the starter solenoid. And if there's a stop solenoid, also supply power to it. It could be a bad relay, a bare wire, or a convoluted control system.

Thanks, I replaced the relays. I was thinking the original problem was a bare wire in the harness, so I removed but then this new spontaneous startup problem occured.

On a boat with a FB, not under a cover of any kind, the start buttons were each covered by a rubber dome. Water got under the dome and shorted out the button, so the engine starter was energised. New rubber dome solved the problem.

Whatever is the cause of the starting until you find it I would disconnect the battery cable to that engine while you aren’t on the boat. If you don’t live aboard you could go home on Sunday and come back on Friday to a running engine.

koliver said:

On a boat with a FB, not under a cover of any kind, the start buttons were each covered by a rubber dome. Water got under the dome and shorted out the button, so the engine starter was energised. New rubber dome solved the problem.

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Almost exactly what I experienced with my present boat. I closed on the boat on a Friday afternoon and went to the marina the following morning to play with my new toy. I found the starboard engine running. I boarded the boat and found there were no keys in the ignition switches so the engine had apparently self-started. I finally found the culprit was an exposed ignition switch on the tower that had filled with water and shorted. There was a rather flimsy rubber cap with a slot for the key that had leaked and allowed water to enter the switch. I removed the starter switches and re-purposed the starter wiring to accommodate some robust waterproof kill switches instead. I also replaced the starter which was damaged when it remained engaged with the engine running. Since the short kept the starter circuit engaged, the run solenoid was also energized which is why the engine continued to run with the ignition switches off. Since I never start the engines from the tower, I eliminated the possibility of that failure ever happening again.

I had a similar but opposite problem with one of the stop switches. It apparently stuck on so the engine wouldn’t start. New switch and problem resolved.

koliver said:

On a boat with a FB, not under a cover of any kind, the start buttons were each covered by a rubber dome. Water got under the dome and shorted out the button, so the engine starter was energised. New rubber dome solved the problem.

Click to expand...

Same problem on a 28' Trojan. New switches were the solution.

Rob

Micro Commander starts your engine? I thought they were just engine controls, mine are at least. Nothing to do with the start/stop circuit. But thinking about it maybe the neutral safety switch in the MC could maybe possibly have something to do with it. Guessing it's more likely starting circuit wiring.

First thing I did with this boat was remove the Micro-Commander in favor of simple Morse. But then I only have the single station. Sold the MC to some poor soul who wanted it, thus paying for the Morse.

Oh my hopes were up that this thread would be about some haunted boat, ghosts starting the engines in the night. I used to own a haunted Cadillac Coupe deVille. First car ever bought straight out of college. $500. Yep, my land boat used to just start on its own also, like your boat. Freaked the kid out who eventually bought it from me when he was sitting in the driver's seat and the car started without him even turning the key. I still remember the look of fear on his face as he turned to his dad "Dad, I didn't touch the key!"

Long story short DrQ, all those guys above are wrong. Your boat is possessed

I’m confused by your original post. Was there some other problem you were tying to fix that led you to reconfigure the micro commander cables, and after that the self starting began?

Or did the self starting begin, and you reconfigured the micro commander cables in an attempt to fix that problem?

"I also replaced the starter which was damaged when it remained engaged with the engine running."

This is very dangerous to your electrical goodies.

A starter IS a DC generator if spun and the gearing of the starter & flywheel will speed it up greatly

FF said:

"I also replaced the starter which was damaged when it remained engaged with the engine running."

This is very dangerous to your electrical goodies.

A starter IS a DC generator if spun and the gearing of the starter & flywheel will speed it up greatly

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Actually the starter drive (bendix) contains an overrun clutch which prevents the the engine from turning the starter in the event the drive fails to disengage. In my case that overrun clutch disintegrated so the starter would no longer engage the flywheel and turn the engine. There was no flywheel ring gear damage though, so the fail-safe design worked.

A good reason to not remove those belt guards.

bayview said:

A good reason to not remove those belt guards.

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+1