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Yanmar 6LPA-STP ... won't shut off and... diagnosis?

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  • 1 Post By coastboater
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Yanmar 6LPA-STP ... won't shut off and... diagnosis?

Old 06-07-2019, 12:44 PM
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Default Yanmar 6LPA-STP ... won't shut off and... diagnosis?

Hey all Yanmar owners... I have a pair of 315hp Yanmar 6LPA-STPs in a 2004 Luhrs 30 Open. There's been 2 different situations recently and i'm wondering if they may be connected, and pointing to a compromise in a switch/something electrical.
This past week the STARBOARD engine shut down 40 miles offshore out of nowhere. no strange noises. no gurgling/stumbling as if fuel/air was being choked off. It seemed like an accidental flip of a kill switch or something, but that was double checked of course and didn't seem to happen. We began troubleshooting everything possible as we limped home on 1 engine. pulled air filters, didn't start. investigated electrical connections and switches. Investigated fuel/water separator and changed a fuel filter. We did get it started after the fuel filter was changed, but i don't exactly recall if it was right after the fuel filter was changed, or if we explored a few other details and then got it running. Whatever it was... we got it running 5 miles outside of the harbor and it's been running fine since.

Next, yesterday my 2nd captain was running a trip and wasn't able to shut the PORT engine off. he tried all the switches (upper/lower helm, etc...) and even shut down everything on the fuse panel... engine kept running. he called me to tell me what was going on, and then of course he was able to shut it down.

Is it possible that the 2 incidents are related? and point to an electrical issue? a switch that's getting moisture in it maybe? or ??? ... maybe it's unlikely that the incidents are connected? just unusual to have 2 weeks in a row with issues that are different, but maybe related? i don't know... any tribal wisdom here? Thanks.
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Old 06-07-2019, 02:32 PM
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For the engine that wouldn't run I would throw the shifter(s) cut out switches into the mix of things to check, but that doesn't fit why the other engine wouldnt cut off.
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Old 06-07-2019, 02:47 PM
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Don't know enough about the Yanmars, but on a CAT diesel, that would detail a problem the fuel cutoff solenoid or its wiring.
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Old 06-07-2019, 03:38 PM
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Pretty much most diesel engines are shut down by a fuel solenoid that stops fuel flow. My Blackfin ALSO had lanyards that could be pulled, to operate the fuel solenoid valve manually. So look for the solenoid, and see first if there is a lanyard to pull, for emergency shut down. Trace solenoid wiring back to the key switch (or button) that is the normal engine shut-off. Key switch ON should open a fuel flow solenoid to allow the engine fuel, to start, and keyswitch OFF should close solenoid to shut it down. Circuitry to shut down a diesel is not very complicated.
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Old 06-07-2019, 06:34 PM
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The 6lp has a fuel shit off solenoid on the injector pump from memory. Pretty sure it is a power on solenoid that is held open when engine is running rather than one that you power up to close the fuel supply. The first issue of shutting down could be a bad connection on the solenoid or in the wiring loom. I have seen both. The engine not shutting off must have somehow held power on the solenoid or the solenoid is sticking. I would be checking the wiring loom connectors for corrosion etc. To identify the solenoid put your ear near the injector pump and listen for a click when you turn the ignition on. There will also probably be a relay click on but that is not on the injector pump.
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Old 06-08-2019, 06:40 AM
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Having owned a Luhrs 32 w Yanmars, I’ve had both of those issues. They were both bad wires from engine to helm. Wiring on my Luhrs was “less than optimum” lol. Definitely fuel solenoid wiring
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Old 06-10-2019, 02:45 PM
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thanks for all the feedback... look forward to diggin into it.

Cheers
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