Generator keeps shutting down

M

MckyD

New Member
Nov 4, 2018
9
Boat Info
Sea Ray 500 1999
Engines
3176 Cats 660hp
Westerbeke Generator 12.5
I have a Westerbeke 12.5 Generator in my Sea Ray 500 1999. I keeps shutting down. I have tried everything from bypassing pressure switches, testing connections, checking oil pressure, water temp and output volts from alternator. When you start the gen set it runs perfectly for anything from 5 min to 20min. Then shuts down. Will restart immediately and run if you hold the preheat switch on. As soon as you let go of the preheat switch it stops. Fuel is ok no problem.
I have had the alternator off and checked to make sure it is running ok. The generator is operated from the main panel in the salon. There are 2 toggle switches and a green light as installed by Sea Ray. When you come to start it for the first time, move the toggle to the run or mid position, the green light come on and you can start and run as normal. Once it starts the green light stays on while running. When it shuts its self down and do to the panel, the green light is off. Even when the run switch is in the run position. If you start and hold the preheat switch on the genset runs and the green light stays on, As soon as you let go of the preheat switch it stops and the green light is out. I have spent days tracing back through the wire diagrams trying to work out the issue. I had a brief chat to a guy this morning who mentioned that some Sea Rays have the fire suspension system hooked into the genset and if there is a fault in the fire system it will shut the genset down. However you would think if that was the case it would not run at all. As I mentioned I really need help with this one.
 
electricaldoctor said:
Have you checked the water pump impeller?
Click to expand...
When its running up to the point it shuts down, I have watched the water temp, oil pressure and volts. All are good.
 
The impeller could still be bad causing high exhaust temp leading to the exhaust temp switch the shut the generator down.
 
We are fighting pretty much the same issue with ours. Same gennie. So far we have replaced a fuel line that was cracked along the port stringer, just before the Racor filter. That seemed to make adifference for a while. Ours will run for hours sometime and 30 minutes others. Ours seems to restart and run fine after the 2nd start.
 
I am not familiar with the 12.5 gennie, but I am familiar with this same problem. Last season (2017) my generator began to act weird. Sometimes it would run for an hour or two with no problems, then would seem to randomly shut down. As the season progressed, the run times became shorter. During last winter's layup, I replaced cap, rotor, plugs, wires, oil filter and oil, and impeller. I also removed the heat exchanger and cleaned it as well. Assured that all was good, the spring of 2018 came an no improvement. Actually, it got worse. Gen would run for 20 minutes on first start up and then die. It would re-start immediately after quitting and I would go through this cycle as many times as I cared to do it. I also checked every sensor and anything else in my service manual. Late in the summer, after posting here, a fellow CSR member suggested checking the oil level in my governor. I had no idea there was oil in there or how in the world it worked. Did some research to find the appropriate amount of oil needed and dove in on a rainy Saturday. Sure enough, only about half the amount (3 oz) of oil needed was present in the governor. Drained the old out, replaced with exactly the correct amount, reinstalled and SUCCESS! Fired the generator and let it run at the dock for 4+ hours without a hiccup. This is a very easy procedure and should be covered in your manual. Check it out.
 
Thanks for getting back to me. You are talking about oil in the engine part of the genset, not the armature???
 
RollerCoastr said:
G, MckyD has a diesel genny, so a solenoid acts as the governor.
Click to expand...

I believe the diesel generator still has a mechanical governor to regulate rpms. It would have a solenoid to shut off the fuel flow to shut down the generator. The oil gdavis is referring to is the oil in the mechanical governor. If it is too low it can't function properly. There is no oil in the armature end of the generator.
 
hottoddie said:
The impeller could still be bad causing high exhaust temp leading to the exhaust temp switch the shut the generator down.
Click to expand...

This is the most likely issue. Either the pickup/strainer is clogged or there is a problem with the pump. The temp gauge you are looking at is for the engine not the exhaust water temperature. All it takes is for water flow to be off by 30-40% for the exhaust manifold to start heating up (engine temp will look normal). My guess is that if you point an infrared temp gun at the exhaust manifold.....you can watch it happening. The trip point should be around 230 degrees.
 
hottoddie said:
I believe the diesel generator still has a mechanical governor to regulate rpms. It would have a solenoid to shut off the fuel flow to shut down the generator. The oil gdavis is referring to is the oil in the mechanical governor. If it is too low it can't function properly. There is no oil in the armature end of the generator.
Click to expand...
Hi
Thought so. It does have a fuel cut off solenoid. I have checked that it is free and slides freely even after it shuts down. I am back on the boat again tomorrow and will once again start working systematically through the circuit and switches. I have bypassed all switches and solenoids. I did think of the alternator. Looking at the wiring diagram, it seems that the circuit that feeds the fuel solenoid, safety switches and lift pump runs through the alternator. One side onto the L terminal and the other on the R terminal. Looking at the alternator that seems to be the case. I did think that it may be an issue with that so I took the alternator off and had it bench tested and was told it was ok.???
 
MckyD. You seem to be ignoring some of the advice given above. PlayDate is an ASE Certified mechanic and suggested that high exhaust temp caused by low water flow is the most likely cause. Just because you have water flow out the exhaust doesn't mean you have adequate water flow to keep the generator from shutting down. I agree with PlayDate, get an inexpensive infrared temp gun and check the exhaust manifold temp as the generator warms up. Second in line would be a problem with the governor. I'm not familiar with the system but if the governor malfunctions and allows the engine to overspeed then it may cause the fuel solenoid to shut off stopping the generator.
 
HI, Thanks for the reply. If you check my previous posts you will see that I have used a infrared temp gun to determine that the temps across the engine, manifolds are consistent with that showing on the temp gauge. I have also accessed the flow rate of the raw water and as a precaution replaced the impeller. Again as per my previous posts. I have also checked the speed to ensure that it is running at the correct speed to give me the correct hertz.
 
hottoddie said:
I believe the diesel generator still has a mechanical governor to regulate rpms. It would have a solenoid to shut off the fuel flow to shut down the generator. The oil gdavis is referring to is the oil in the mechanical governor.
Click to expand...

I might be thinking about a different unit. A friend of mine had the same boat and I thought the same genny, but I thought we called it a 12 instead of a 12.5? At any rate, his didn't have a mechanical governor like my BCG does.
 
I'm still not convinced you don't have a water flow problem.

Why? Because the symptoms you describe are identical to a safety tripping. Runs for a while.....shuts down....will only run with the pre-heat held down. If, after 20 minutes it restarts and runs without holding the pre-heat switch......it is related to the safeties. The pre-heat bypasses the safeties to energize the fuel pump. Of the safeties.....the most likely candidate is the exhaust water temperature safety since you can monitor the oil pressure and engine temperature on your gauges which makes troubleshooting a lot easier.

A governor problem behaves differently. First, it doesn't care about the pre-heat switch on a restart. Second, you can hear it surging.

I don't know the history of your boat's generator but given the symptoms and restart behavior....my money is on a water flow problem. It can be:

-A clogged raw water intake
-A clogged strainer
-A clogged heat exchanger
-A bad impeller
-A badly scored pump
-A bad sensor

As hottoddie said....having water flow is not enough. It has to be enough to cool the heat exchanger and exhaust. It is probably something that you have already looked and thought was okay. It's okay to look for more suggestions but with only four safeties and the behavior of a safety shutdown......that's where I would focus.

BTW the green light shows the normal status of the control board. It too is behaving on a quick restart as a safety has been tripped.
 
Ok, I am at the boat again today, however the question is what part does the alternator play in all this? The circuit runs through the safety switches, fuel solenoid and lift pump before ending up at the alternator and connected to the R on the back of the alternator. There is another wire connected to the L terminal on the back that also runs back through the same circuit. My thought was that when you flick the preheat it supplies power to the circuit and when the genset starts up the alternator supplies power to the circuit and if that is the case then there could be an issue with the alternator where after a time it opens the circuit stops supply to this circuit and the genset shuts down. I have also had a chat with a guy yesterday that suggested that the fire suppression system is connected through the circuit and if so and there was an issue with that system it could be shutting it down.
 
MckyD said:
HI, Thanks for the reply. If you check my previous posts you will see that I have used a infrared temp gun to determine that the temps across the engine, manifolds are consistent with that showing on the temp gauge. I have also accessed the flow rate of the raw water and as a precaution replaced the impeller. Again as per my previous posts. I have also checked the speed to ensure that it is running at the correct speed to give me the correct hertz.
Click to expand...

I went back over your posts and this is the first mention of an infrared thermometer. Checking all over the engine with the IR thermometer and having it agree with your analog temp gauge is fine but did you check the temp at the exhaust manifold/hose where the exhaust temp shutdown sensor is located? You can have enough water flow to cool the engine but that may not be enough to keep the exhaust system from overheating. Will the generator shut down more quickly when under heavy load than under no load. If so it would point even more to an overheat shutdown.
 
Generally speaking....alternators, fire suppression systems and control boards are binary.....they either work or they don't. I believe your generator has a DC safety but again it doesn't fit the story you have told. Your voltmeter gauge would also show any problems with the alternator.

Sometimes a broken wire/connector can exhibit the issues you have but it eventually gets to the point that the generator won't run at all which makes it easier to find the problem. Broken wires are almost always DC + wires which have intermittent integrity. However, a broken wire does not fit your restart story. In most cases, a broken wire will restart fine and continue to run for a short while without the preheat switch.

It still is worthwhile to check the harness. If the generator will start and run, pull on the wire harness and connectors to see if it will shutdown.


Regarding the alternator:
R usually means: Exciter terminal where power comes from the purple wire to energize the alternator.
L usually means: Indicator Lamp
 
hottoddie said:
I went back over your posts and this is the first mention of an infrared thermometer. Checking all over the engine with the IR thermometer and having it agree with your analog temp gauge is fine but did you check the temp at the exhaust manifold/hose where the exhaust temp shutdown sensor is located? You can have enough water flow to cool the engine but that may not be enough to keep the exhaust system from overheating. Will the generator shut down more quickly when under heavy load than under no load. If so it would point even more to an overheat shutdown.
Click to expand...
Sorry, my mistake. The posts were on another for
PlayDate said:
Generally speaking....alternators, fire suppression systems and control boards are binary.....they either work or they don't. I believe your generator has a DC safety but again it doesn't fit the story you have told. Your voltmeter gauge would also show any problems with the alternator.

Sometimes a broken wire/connector can exhibit the issues you have but it eventually gets to the point that the generator won't run at all which makes it easier to find the problem. Broken wires are almost always DC + wires which have intermittent integrity. However, a broken wire does not fit your restart story. In most cases, a broken wire will restart fine and continue to run for a short while without the preheat switch.

It still is worthwhile to check the harness. If the generator will start and run, pull on the wire harness and connectors to see if it will shutdown.


Regarding the alternator:
R usually means: Exciter terminal where power comes from the purple wire to energize the alternator.
L usually means: Indicator Lamp
Click to expand...
Ok thanks. I will be checking once again all the connection and harness later today. Also, I have put the IR over all the engine including the exhaust manifold. All good. Not forgetting that I have also bypassed the temp switch on the manifold. Also, the load does not make any difference.
 
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