Westerbeke 7.0 BCG shutting down

[J Levine]

My generator shut down system was giving me some troubles today. I had the gennie running for about 2 hours steady both while cruising and on the hook when for no apparent reason is just shut down. I went into the engine room and checked the oil level which was fine, and put my hand on the exhaust riser to see if it was hot to the touch and it was not. Before I left I had cleaned the sea strainer so I figured that was not a problem. I then restarted the unit which started right up, I checked the exhaust water flow which looked fine. It took a full load and ran for another 2 hours before shutting down again. This time when I restarted it it ran for a few minutes and the shut down again. I was already back at my slip so I went to shore power and figured I would mess with it next weekend when all that iron in the engine room is not so hot.

So I understand the shut down system has three sensors: oil pressure, water temperature and exhaust riser temperature. I also understand that all of these sensors are normally closed, going open when they are tripped. Any guidance on how to trouble shoot this one or common causes of this problem? I am thinking I have a bad sensor or a loose wire somewhere. This is the first time this has ever happened in the 5 years I have owned the boat and I generally run the generator quite frequently. It has about 700 hours on it. Over the years I have changed the plugs, fuel filter, riser, water impeller, fan belt, governor oil, and had the heat exchanger professionally cleaned.

Appreaciate your thoughts and experiences.

Jon

 

[Presentation]

Jon,

You are going at it with the same logic I would.

Does it rev high before it shuts down?

RPM is another sensor.

 

[fc3]

That's it for the mechanical sensors. There is one more sensor that's electronic. It shuts down the engine on overspeed (as Doug stated) and high voltage. Don't think it does a shut down for low speed or low voltage.

The obvious way to test the mechanical sensors is to put an ohm meter on then right after the engine shuts down. Since the engine is not running, oil pressure will be open, but the two temperature ones probably have not cooled down enough to close. Now I have a trick for checking fault switches that I've used in the past and it works OK.

There is a relay in the Westerbeke generator that is held on by the shutdown module, the two temperature switches, and the oil pressure switch. Generally, these 12V relays draw about 10 mA. Therefore, if you put a very small fuse in parallel with each switch, when the switch opens, the relay's field coil current will pass though the fuse, burning it out. The burnt out fuse indicates the tripped safety. Use the fastest acting, smallest current value fuse you can find 1 or 2 mA or less would work. Littlefuse makes a bunch of models that would work. If the genset shuts down without blowing a fuse, it's the shutdown module or an engine problem with fuel delivery or ignition.

Best regards,
Frank

 

[PlayDate]

Jon,

It is the second restart and two hour run time that leads me to think it is not the safety sensors (everybody blames them). I am suspicious of a broken or lose wire (700 hours of vibration causes them) or a fuel delivery issue.

The first one is easy to check. With the generator running tug and pull on the wiring harness wherever you see connections. If it is a broken wire, the unit will shut down and you have found the problem.

Fuel delivery is harder to check. The system has a in-line fuel filter, an electric fuel pump and a shut down solenoid that cuts off the fuel supply. My bet is the fuel pump is starting to fail. One of the key signs that it is starting to have issues is random shutdowns. The only way to check it is to install a fuel pressure gauge after the fuel pump and monitor it. Westerbeke fuel pumps run about 4lbs of pressure.

While it is possible it could be several other things, I would eliminate the most common possible non-maintenance failure issues first. It sounds like you take great care of the unit so I doubt it is maintenance related which is what activates the safetys.

Let me know what you find,

John

 

[J Levine]

Great advice guys. This has the making of one a PITA anoyance to track down. I didn't notice any change in speed, the thing just shuts down like you turned it off. I would think if the fuel pump was on its way out it would kind of sputter to a stop? I will do the wire wiggle test and plan on trobleshooting the problem with more effort the next time it happens. I grabbed the service manual before I left this morning to do some studying at home (I also started and ran the genie for a few minutes with no issues). Any idea what temperature these sensors are susposed to open up? I have a infared temp gun that I can use to check the temps the next time it happens.