Kohler 12.5 RCOP67 Generator Problem

[richard5933]

It was time for the monthly generator run so I went out to the coach and got the old Kohler up and running. Took a few tries but it did start and come to life. I probably didn't hold the preheat button long enough to start the first time. The old Perkins is a bit tired, but the oil pressure came up in a very short time and the engine evened out at a smooth idle. Not bad considering it's in the 20s today and the Perkins has no block heater.

I turned on the electric heaters in the coach to put on a load, about 5,000 watts total, and things seemed okay. However, after about 10 minutes the engine just shut off for no apparent reason. Oil pressure seemed okay, and temp was still climbing and was just above 140F. I tried to restart but the engine just turned with not even the slightest hint of starting. I went to the generator bay to try it there so I could listen to what happened. When I turned the switch to 'run', the usual loud click of the fuel solenoid was absent. Then I noticed that the "cranking reset" red button had tripped and was sticking out. I was able to push it back in till it clicked. After that the engine started but only ran for about 30 seconds before shutting down again. I repeated this a couple of more times with the same result.

There was no sign of catastrophic failure - no oil leaking, no antifreeze leaking, and all fluids looked okay. After about 15 minutes of letting things rest, I tried again. The engine started and ran fine. It stayed running this time. I let it run for a few minutes from the generator bay, and then shut down to check again for obvious problems. Things seemed okay so I tried again from the main panel inside. Again the engine started and ran fine. Oil pressure was steady about about 45 psi. Temp was slowing rising then suddenly climbed to 170. It was starting to go higher, and just as I was reaching for the shut-down switch it dropped back to a little over 140 and started to climb slowly again. I ran it for about half an hour total while I watched the gauges. Enough to check off the 'run generator' item off my monthly checklist.

Now I have to add 'diagnose generator' to the list.

Here's my thoughts:

1. Seems like something triggered an automatic shut down. I'm not totally sure how the shut down circuit works in the Kohler control box, but the fact that the 'cranking reset' button popped out points me towards this. Add to that the fact that upon initial reset it ran for about 20 seconds and shut down again, and I'm pretty sure that some type of auto shut down circuit is in play here.
2. The temperature gauge climbing suddenly to just over 170 and the dropping back to 140 leads me to think that I've got a sticking thermostat. Possibly this caused the shut down, but I'm not sure. I didn't see the gauge at the moment of shut down.
3. When I checked the engine after the initial shut down, the lower radiator hose was warm but the tank and upper hose was cold. This adds to my theory that a sticking thermostat was in play here.

I've checked the manuals I have for the generator that I downloaded from the Wanderlodge site, but none of them mention the red 'cranking reset' button, so I really have no idea where that plays in the system or if it's in the auto-shutdown circuit.

I would love to hear what others think could be at play here. Maybe someone has more familiarity with the auto shut down on the old Kohlers that can add some wisdom here.

[dickandlois]

Richard, Think checking the Thermostat is kind of at the top of the list. Cold weather can cause them to do strange things, also I'm sure you have checked the freeze point, knowing where you live. Is the water pump belt driven? Cold stiff belts can cause issues, how is the belt tension? 

Back to the thermostat - I have had the top saddle that holds the spring in place split at the top and then they do not open properly! The valve assembly twists sideways.

Rich.

[bm02tj]

Have you added antigel or filled up with winter fuel 

[manholt]

Thermostat and stiff/slipping belt.  When did you last do a full service and inspection of the belt?  

[richard5933]

8 hours ago, DickandLois said:

Richard, Think checking the Thermostat is kind of at the top of the list. Cold weather can cause them to do strange things, also I'm sure you have checked the freeze point, knowing where you live. Is the water pump belt driven? Cold stiff belts can cause issues, how is the belt tension? 

Back to the thermostat - I have had the top saddle that holds the spring in place split at the top and then they do not open properly! The valve assembly twists sideways.

Rich.

Water pump was replaced last spring, as was the antifreeze. I know that the freeze point is good. I'll have to check that the shop got the belt on correctly and that it's in good shape. For some reason hadn't even though about checking the water pump situation. Thermostat is separate from water pump, so it wasn't done, I'll have to r/r once it's warm enough to work outside again.

 

4 hours ago, bm02tj said:

Have you added antigel or filled up with winter fuel 

Yes & yes. Draws from the same tank as the main engine, and there is good fuel with antigel in it.

[jleamont]

Richard, replace the radiator cap also, most don't realize how critical it is, that cap can cause serious engine problems down the road. I'm assuming you have checked the SCA's in the coolant recently and Diesel spec coolant was put into the generator when the pump was replaced? 

[richard5933]

35 minutes ago, jleamont said:

Richard, replace the radiator cap also, most don't realize how critical it is, that cap can cause serious engine problems down the road. I'm assuming you have checked the SCA's in the coolant recently and Diesel spec coolant was put into the generator when the pump was replaced? 

Coolant was replaced with the same as is in the 8V71 in the spring. Don't see any reason it would go bad between then and now. I did check level in the fall when winterizing.

The radiator cap looked good at the fall check. Not sure it's the problem here, as it was still cold yesterday during the problems. The lower hose was warm, but the upper tank (which is separate from the radiator on our installation) and upper hose were still cold. This was why I suspect a sticking or malfunctioning thermostat. Seems like the tank would still be warm, even with a faulty cap, if the coolant were flowing through the upper tank. I will have to check for an air pocket today now that the Perkins is cooled down.

[jleamont]

35 minutes ago, richard5933 said:

Coolant was replaced with the same as is in the 8V71 in the spring.

Was it the proper coolant for a Diesel with SCA's in it or was it converted to OAT coolant?

[richard5933]

It was the proper diesel rated coolant. No conversion to OAT.

[manholt]

Richard.  

In the past 16 hours, you have had a lot of input, from folks that know far more than me...I guess it was stuff that you already knew!  

[richard5933]

2 hours ago, manholt said:

Richard.  

In the past 16 hours, you have had a lot of input, from folks that know far more than me...I guess it was stuff that you already knew!  

The water pump/belt issue which was mentioned had not occurred to me at all. That gives me something new to investigate.

The bigger issue I'd also like to understand more is how the "cranking reset" button and the related circuit works. I can't find it on the manuals I have. Hoping someone has some experience with this.

 

[dickandlois]

            The bigger issue I'd also like to understand more is how the "cranking reset" button and the related circuit works. I can't find it on the manuals I have. Hoping someone has some experience with this.

Richard, Thinking that the generator might not have warmed up enough to be running at the proper speed before you added the 5000 Watt load. This could very easily caused a higher current level, because frequency and current are closely related in this case. 

     When you find the cooling issue, run the generator a little longer when it is real cold out before placing a large load on it - something like a 60 watt incandescent light should not cause enough load to trip the protection circuit in warm up cycle.

Rich.

[manholt]

On every coach with a generator, that I have ever owned, it says in the owners manual, that after you start the generator, let it warm up for 2 minutes (longer in cold weather), before putting a 25% load on!  Then gradually increase load to full.  My 10 kw does it automatically...same with my 18 kw at the beach house!

Also, turn off heavy draw units, like AC and wait 2 minutes, before turning unit off.

The above is for both Gas, Diesel or Propane!

Is your's a one or two stage unit?  My 10 is one stage, the 18 is 2.

[richard5933]

1 hour ago, DickandLois said:

            The bigger issue I'd also like to understand more is how the "cranking reset" button and the related circuit works. I can't find it on the manuals I have. Hoping someone has some experience with this.

Richard, Thinking that the generator might not have warmed up enough to be running at the proper speed before you added the 5000 Watt load. This could very easily caused a higher current level, because frequency and current are closely related in this case. 

     When you find the cooling issue, run the generator a little longer when it is real cold out before placing a large load on it - something like a 60 watt incandescent light should not cause enough load to trip the protection circuit in warm up cycle.

Rich.

Good thought. Do you know if the "cranking reset" is connected with just the engine protection circuits (high temp & low oil) or if it's also connected with the generator output? When it trips, the engine shuts off immediately since it controls the fuel solenoid. The output circuit breakers never tripped at all.

Next time I'll let it warm up a bit more and see what happens.

[dickandlois]

3 hours ago, richard5933 said:

Good thought. Do you know if the "cranking reset" is connected with just the engine protection circuits (high temp & low oil) or if it's also connected with the generator output? When it trips, the engine shuts off immediately since it controls the fuel solenoid. The output circuit breakers never tripped at all.

Next time I'll let it warm up a bit more and see what happens.

Richard, A question I do not have direct knowledge on, however! I have a thought running around in may head. Remember the calculator is not as quick anymore.

      Does the generator start off it's own battery in your system?

If the battery is charged directly from a bridge 12 volt rectifier board or from a electronic speed control circuit(Different gen builders introduced things over different time lines. You Diesel engine setup was most likely built when I was in high school or a freshman in collage and I thought they where using smock and mirrors to totally mess me up. LOL

     Your setup may very well have a mechanical governor - that removes most of any electronics and at a time when they where  using the old diodes(Germanium) that smelled like rotten eggs when they failed where in vogue. This is where the gap in may information falls short - Nothing on the dynamo wiring and electrical interface. 

    I know you have skill levels many do not have, so if you can trace the wiring from the circuit breaker back to a origin - we might be able to open a few doors. Known info. it is a 12 volt circuit.

Rich.

 

      

[richard5933]

Rich - Not sure if I can answer all this, but here's what I know...

The bus has a 24v system for the engine and chassis systems. That is not connected to the generator at all.

The house systems are 12v, and they are not connected to the generator at all.

The generator has its own start battery which is brand new. Engine is definitely before any electronics at all. The governor is strictly mechanical. When the engine runs it runs well. There is a battery charging circuit in the Kohler control box, but we don't use it. When the generator is not being run I've got a Xantrex Echo Charger to keep the generator start battery topped off. After starting the generator, I bridge the generator battery to the house battery bank so that it can be charged from the 70-amp 12v charger that also charges the house batteries. There is no alternator on the generator. I could use the on-board charging circuit, but for two reasons I don't. The on-board charging circuit is not a smart charger and can over-charge the start battery, and the on-board charging circuit is really weak.

When I was running things yesterday, the generator head and its systems appeared to work as they should. I had a steady 119 volts with about a half load on the system. The dual 30-amp output breakers on the generator control box did not trip and seemed to not be involved in this at all.

The only thing that tripped was the red "cranking reset" button on the front of the control box. Since it's not shown in the wiring diagram that's in the book from Custom Coach (yup - I've got the original manual and wiring diagrams from CC) so I will have to trace the circuit manually. However, it's really really cold right now (teens) and I just don't have the gumption to be out there doing this now. Since we are not going to use the coach till early spring, I'm in the research stage right now so I can be armed and ready once the temps start to rise again.

I did check the belt today on the water pump. It's in good condition and properly tightened. It does spin with the engine so I assume the water pump is spinning. Of course, it's a new water pump so there is always the possibility it failed, but that's unlikely (especially since things did start working yesterday after the initial problems).

My first step will be to change the thermostat. Right now I've sent a note to a supplier in the UK trying to get information on the proper thermostat for this engine in this application. Probably a standard 180-degree stat, but I wanted to be sure.

Next I will have to trace the circuit to see what could possibly trigger the "cranking reset" to trip. Probably going to find it connected to the oil pressure and high-temp switches, so I'll have to confirm that they are functioning properly.

We're not in any type of crisis mode here, but I do want to figure out what caused the problem so that when we hit the road in the spring I don't suddenly find that we don't have a functional generator.

[richard5933]

Of course, this thread that I just finally found may have the answers I'm looking for.

https://www.smokstak.com/forum/showthread.php?t=175356&page=2

I've started reading through it and it sounds like someone had similar issues and a post in the thread walks through the operation of the crank reset circuit.

I'm open to other suggestions as well.

Strange thing is that it worked for a year since we had the bus, suddenly failed yesterday, and now is apparently working again.

Perhaps some moisture got into a switch/relay and froze up the works?

[bm02tj]

Did your gen have a good run after you added antigel so it would be all the way to gen 

[manholt]

Huh?  Must have missed that part.

[richard5933]

27 minutes ago, bm02tj said:

Did your gen have a good run after you added antigel so it would be all the way to gen 

Yes - definitely is something in the 'crank reset' circuit and not fuel related. Right now I'm trying to narrow down what caused the 'crank reset' button (breaker??) to pop out and shut down the engine. From reading the other thread I posted just before, it seems like there are only three things that play into the 'crank reset circuit' - low oil pressure, high temp, and coil/crank clearing. I don't yet know what the coil/crank clearing is, but the other two showed okay on the gauges so if they tripped the system then I've got a faulty switch somewhere. I'll do some circuit tracing once the outside temps get above 40-ish again.

[manholt]

I think you over heated the engine and the CC closed.  If your temp gauge is bad, then the 170 degree, that you saw, could have been in reality over the 220+ threshold !  So, we wait another 5 months to find out the answer...?  

[richard5933]

36 minutes ago, manholt said:

I think you over heated the engine and the CC closed.  If your temp gauge is bad, then the 170 degree, that you saw, could have been in reality over the 220+ threshold !  So, we wait another 5 months to find out the answer...?  

You could be correct, but the gauge has been at that point over the summer during normal operation - hovering between 170 and 175 - for hours without a problem. Never saw the gauge go over that this time. But, the temp gauge might not have been reading actual temp. It's sticking into the water to read temp, and if there was an air pocket or other weirdness from a stuck thermostat it might have been getting a false reading. The temp gauge uses a separate sending unit from the one in the shut-down circuit, so it's possible for one to read normal and the other to read overheat. When I saw the gauge suddenly climb and then go back down, I'm guessing that's when the thermostat finally opened. I hope no damage was done, but no real way to tell just yet. Once things got going again the engine appeared to run okay, and there is no noticeable water in the oil or oil in the water. Fortunately, if overheat was the problem, the shut down system does work.

Hopefully not five months till I can investigate - last year I was able to get a little work done during the winter with a few days here and there with temps above 40 degrees, and by early March we start having enough sun during the day to warm things just a tad and get a at least a couple of days a week where I can work outside on the coach.

[wildebill308]

Richard, have you checked the actual temp with a IR thermometer?

Bill

 

 

[dickandlois]

9 hours ago, richard5933 said:

Of course, this thread that I just finally found may have the answers I'm looking for.

https://www.smokstak.com/forum/showthread.php?t=175356&page=2

I've started reading through it and it sounds like someone had similar issues and a post in the thread walks through the operation of the crank reset circuit.

I'm open to other suggestions as well.

Strange thing is that it worked for a year since we had the bus, suddenly failed yesterday, and now is apparently working again.

Perhaps some moisture got into a switch/relay and froze up the works?

Richard, Looks like I would have expected and the verbal explanation adds some extra information, that helps the the weak print at spots in the drawing.

The battery charging circuit is designed like ones used to charge small lawn tractors, so the setup you adapted for yours is in all respects  was a good move.

Sweet find !

Rich.