Onan shuts down under load without shutdown codes


Slavko Despotovic
 

Wrong this time. Heat exchanger had to be cleaned. Few hours of cleaning and now the temperatures are 73dC and 23dC. Sea water temperature is 15dC.
Thank you all for help.

--
Slavko
SM 2000
#279 Bonne Anse in Portoroz


Slavko Despotovic
 

I cleaned exhaust elbow, and cleaned manifold. White smoke is gone, but overheating not. I am now left, my opinion, with heat exchanger and thermostat. The flow of the seawater is stronger then it was before the cleaning, so I am more to the direction of faulty thermostat.
Do I have to drain a coolant from the engine to check on the thermostat?
--
Slavko
SM 2000
#279 Bonne Anse in Portoroz


Porter McRoberts
 

For what it’s worth I also think its a clogged exhaust elbow. Easy to remove and clean. Very similar symptoms on our Onan: steam but caught it before the shutdown scenarios started. There’s something very satisfying about cleaning out that elbow!  
Good luck!



Porter McRoberts 
S/V IBIS A54-152
WhatsApp:+1 754 265 2206
Www.fouribis.net

On May 1, 2021, at 6:14 AM, CW Bill Rouse <brouse@...> wrote:


Based on the temperatures you gave I am convinced the white smoke is steam. 

Here is another photo showing how carbon can build up in the exhaust manifold and exhaust elbow. And even though the buildup of carbon is slow and over time and slowly increasing the operating and exhaust elbow temperatures, the shutdown will be immediate when the temperatures reach the "cut-off temperature. In other words, it might take a year to build up enough carbon to shut down the Onan, with it working fine for a year and today shutting down.  Once you find the issue, monitor those two temperatures frequently. If something like carbon buildup is happening you will see a slight increase in temperature over time until you finally get a "shut-down."

<image.png>

CW Bill Rouse Amel Owners Yacht School
Address: 720 Winnie, Galveston Island, Texas 77550 
View My Training Calendar


On Sat, May 1, 2021 at 9:30 AM Craig Briggs via groups.io <sangaris=aol.com@groups.io> wrote:
I can never remember what white, blue or black smoke mean. Here's a good refresher from a Steve D'Angelo article last year in Cruising World.
 

"White smoke from a marine diesel engine is one of the most difficult symptoms to diagnose because a number of factors can point to two general causes: overcooling, whereby the cylinder head and combustion chambers operate at a temperature that’s too low for proper combustion; and piston-ring blowby, which indicates low compression and poor combustion.

White smoke represents atomized fuel, very small droplets of fuel that form a fog of sorts. It’s common, and quite normal, to see this when a cold engine is started and until it warms up. If, however, a preheat device such as glow plugs or an air-intake heater are malfunctioning, the production of white smoke may be excessive and longer lasting. In extreme cases, the engine may be difficult or impossible to start.

Fuel of poor quality, particularly fuel that’s off spec or not properly formulated as Number 2 diesel, will burn poorly, which in turn may produce white smoke. Adding a fuel cetane booster may temporarily alleviate—and identify—this problem.

 

Other causes of white smoke coming out of boat exhaust are poorly adjusted valves or worn valve seats, a partially activated decompression lever, a blown head gasket, or a cracked cylinder head or cylinder liner. A mechanic with the proper tools can narrow down the suspects.
Engine Tip: White smoke can indicate overheating, but the “smoke” is actually steam that’s produced in the exhaust system rather than as a result of an overheating engine. This may occur, for instance, because of restrictions in the injected elbow. To test for this, measure water temperature in the “wet” portion of the exhaust hose; it should be below 200F.

 
Black Smoke
 

This indicates the presence of unburned or partially burned fuel. The most common cause for this is overloading, sometimes referred to as overfueling because more fuel is fed into the engine than it can efficiently burn. This can occur, say, when a sailboat is docking and the engine is momentarily gunned, emitting a puff of black smoke. A constant plume of black while running under heavy load, or even at ordinary cruising rpm, is evidence of chronic overfueling, typically caused by a propeller with too much pitch or too great a diameter. Or it may be that the prop is fouled; just a few hard barnacles are all it takes. Worn, carbon-encrusted, or malfunctioning injectors or a clogged or wet air filter may also be to blame for black smoke.

Blue Smoke
 

This, on the other hand, is typically created when crankcase oil is burned in the engine’s combustion chambers, possibly causing carbon buildup there. Worn valve stems or guides (stems are the thin shafts on exhaust and intake valves; guides are the tubes in which they move) can let oil sneak past to mix with the fuel. Because oil is a much heavier distillate than diesel, it doesn't burn completely, which results in carbon formation and blue smoke. Determining which culprit has produced the blue smoke—the valve stems and guides, or the piston rings—calls for a cylinder differential leak-down test, a procedure that can be performed by a diesel mechanic. It requires compressed air, so it’s typically carried out at a boatyard.

 
 
SN68 Sangaris, Tropic Isle Harbor, FL


 

Based on the temperatures you gave I am convinced the white smoke is steam. 

Here is another photo showing how carbon can build up in the exhaust manifold and exhaust elbow. And even though the buildup of carbon is slow and over time and slowly increasing the operating and exhaust elbow temperatures, the shutdown will be immediate when the temperatures reach the "cut-off temperature. In other words, it might take a year to build up enough carbon to shut down the Onan, with it working fine for a year and today shutting down.  Once you find the issue, monitor those two temperatures frequently. If something like carbon buildup is happening you will see a slight increase in temperature over time until you finally get a "shut-down."

image.png
CW Bill Rouse Amel Owners Yacht School
Address: 720 Winnie, Galveston Island, Texas 77550 
View My Training Calendar


On Sat, May 1, 2021 at 9:30 AM Craig Briggs via groups.io <sangaris=aol.com@groups.io> wrote:
I can never remember what white, blue or black smoke mean. Here's a good refresher from a Steve D'Angelo article last year in Cruising World.
 

"White smoke from a marine diesel engine is one of the most difficult symptoms to diagnose because a number of factors can point to two general causes: overcooling, whereby the cylinder head and combustion chambers operate at a temperature that’s too low for proper combustion; and piston-ring blowby, which indicates low compression and poor combustion.

White smoke represents atomized fuel, very small droplets of fuel that form a fog of sorts. It’s common, and quite normal, to see this when a cold engine is started and until it warms up. If, however, a preheat device such as glow plugs or an air-intake heater are malfunctioning, the production of white smoke may be excessive and longer lasting. In extreme cases, the engine may be difficult or impossible to start.

Fuel of poor quality, particularly fuel that’s off spec or not properly formulated as Number 2 diesel, will burn poorly, which in turn may produce white smoke. Adding a fuel cetane booster may temporarily alleviate—and identify—this problem.

 

Other causes of white smoke coming out of boat exhaust are poorly adjusted valves or worn valve seats, a partially activated decompression lever, a blown head gasket, or a cracked cylinder head or cylinder liner. A mechanic with the proper tools can narrow down the suspects.
Engine Tip: White smoke can indicate overheating, but the “smoke” is actually steam that’s produced in the exhaust system rather than as a result of an overheating engine. This may occur, for instance, because of restrictions in the injected elbow. To test for this, measure water temperature in the “wet” portion of the exhaust hose; it should be below 200F.

 
Black Smoke
 

This indicates the presence of unburned or partially burned fuel. The most common cause for this is overloading, sometimes referred to as overfueling because more fuel is fed into the engine than it can efficiently burn. This can occur, say, when a sailboat is docking and the engine is momentarily gunned, emitting a puff of black smoke. A constant plume of black while running under heavy load, or even at ordinary cruising rpm, is evidence of chronic overfueling, typically caused by a propeller with too much pitch or too great a diameter. Or it may be that the prop is fouled; just a few hard barnacles are all it takes. Worn, carbon-encrusted, or malfunctioning injectors or a clogged or wet air filter may also be to blame for black smoke.

Blue Smoke
 

This, on the other hand, is typically created when crankcase oil is burned in the engine’s combustion chambers, possibly causing carbon buildup there. Worn valve stems or guides (stems are the thin shafts on exhaust and intake valves; guides are the tubes in which they move) can let oil sneak past to mix with the fuel. Because oil is a much heavier distillate than diesel, it doesn't burn completely, which results in carbon formation and blue smoke. Determining which culprit has produced the blue smoke—the valve stems and guides, or the piston rings—calls for a cylinder differential leak-down test, a procedure that can be performed by a diesel mechanic. It requires compressed air, so it’s typically carried out at a boatyard.

 
 
SN68 Sangaris, Tropic Isle Harbor, FL


Craig Briggs
 

I can never remember what white, blue or black smoke mean. Here's a good refresher from a Steve D'Angelo article last year in Cruising World.
 

"White smoke from a marine diesel engine is one of the most difficult symptoms to diagnose because a number of factors can point to two general causes: overcooling, whereby the cylinder head and combustion chambers operate at a temperature that’s too low for proper combustion; and piston-ring blowby, which indicates low compression and poor combustion.

White smoke represents atomized fuel, very small droplets of fuel that form a fog of sorts. It’s common, and quite normal, to see this when a cold engine is started and until it warms up. If, however, a preheat device such as glow plugs or an air-intake heater are malfunctioning, the production of white smoke may be excessive and longer lasting. In extreme cases, the engine may be difficult or impossible to start.

Fuel of poor quality, particularly fuel that’s off spec or not properly formulated as Number 2 diesel, will burn poorly, which in turn may produce white smoke. Adding a fuel cetane booster may temporarily alleviate—and identify—this problem.

 

Other causes of white smoke coming out of boat exhaust are poorly adjusted valves or worn valve seats, a partially activated decompression lever, a blown head gasket, or a cracked cylinder head or cylinder liner. A mechanic with the proper tools can narrow down the suspects.
Engine Tip: White smoke can indicate overheating, but the “smoke” is actually steam that’s produced in the exhaust system rather than as a result of an overheating engine. This may occur, for instance, because of restrictions in the injected elbow. To test for this, measure water temperature in the “wet” portion of the exhaust hose; it should be below 200F.

 
Black Smoke
 

This indicates the presence of unburned or partially burned fuel. The most common cause for this is overloading, sometimes referred to as overfueling because more fuel is fed into the engine than it can efficiently burn. This can occur, say, when a sailboat is docking and the engine is momentarily gunned, emitting a puff of black smoke. A constant plume of black while running under heavy load, or even at ordinary cruising rpm, is evidence of chronic overfueling, typically caused by a propeller with too much pitch or too great a diameter. Or it may be that the prop is fouled; just a few hard barnacles are all it takes. Worn, carbon-encrusted, or malfunctioning injectors or a clogged or wet air filter may also be to blame for black smoke.

Blue Smoke
 

This, on the other hand, is typically created when crankcase oil is burned in the engine’s combustion chambers, possibly causing carbon buildup there. Worn valve stems or guides (stems are the thin shafts on exhaust and intake valves; guides are the tubes in which they move) can let oil sneak past to mix with the fuel. Because oil is a much heavier distillate than diesel, it doesn't burn completely, which results in carbon formation and blue smoke. Determining which culprit has produced the blue smoke—the valve stems and guides, or the piston rings—calls for a cylinder differential leak-down test, a procedure that can be performed by a diesel mechanic. It requires compressed air, so it’s typically carried out at a boatyard.

 
 
SN68 Sangaris, Tropic Isle Harbor, FL


 

I doubt it is the thermostat because of the temperatures you have.
CW Bill Rouse Amel Owners Yacht School
Address: 720 Winnie, Galveston Island, Texas 77550 
View My Training Calendar


On Sat, May 1, 2021 at 8:55 AM Vladan SV PAME <vladan.bojic@...> wrote:
Slavko,

White smoke means there is no sea water flow.
Once you fix sea water flow you will need to change impeller as it's burned now without sea water.

Happened to me same with engine.
--
Vladan

A54 #157 PAME


Vladan SV PAME
 

Slavko,

As you just changed impeller another possibility is that some impeller fin or something else get stacked and omit normal sea water flow.
--
Vladan

A54 #157 PAME


Craig Briggs
 

Slavko,
Unlikely, but, sure, a bad thermostat could cause the problem.
You might try removing the thermostat and either test it in a pan of water on the stove or run the set without the thermostat and see if it still overheats.
Then you will know.


Vladan SV PAME
 

Slavko,

White smoke means there is no sea water flow.
Once you fix sea water flow you will need to change impeller as it's burned now without sea water.

Happened to me same with engine.
--
Vladan

A54 #157 PAME


Slavko Despotovic
 

Thank you. Impeller is new. Replaced two hours ago. Bad thermostat would not cause this type of problems?
I am little confused as generator worked fine before maintenance few hours ago. 

Water is coming out of the boat. There is one more think, after 5-10 minutes there is white smoke starting to come out  of exhaust, combined with water. This is something that did not happen before.
--
Slavko
SM 2000
#279 Bonne Anse in Portoroz


 

The operating temperature (oil) should be about 80C and the exhaust elbow about 50C.

The issue is that you are not getting enough saltwater through the heat exchanger.

The causes are multiple, but could be one of these more common causes:
  1. The supply of saltwater to the Onan may be restricted. Check the sea chest strainer and the primary saltwater manifold (photo below) connected to the sea chest. You may need to check hoses from the sea chest to the Onan raw water pump.
  2. The impeller blades are worn, broken, cracked, or set in place causing the lack of flow. Your Onan needs OEM impellers that are changed every 250 hours or 1 year, whichever comes first. Just because you see water exhausting the boat, doesn't mean it is enough water and it does not mean the impeller is good. I cannot tell how much water is enough by looking at the exhaust.
  3. Impeller blades may be logged inside the Onan raw water pump. Remove the pump and inspect for blades.
  4. The impeller is held in place by a key. The key will wear and sometimes cause the shaft to spin inside the impeller. This is hard to recognize.
  5. The heat exchanger and/or hoses connected are partially clogged with broken blades and/or debris. Remove the heat exchange and have it professionally cleaned. Take this opportunity to repaint it and install a new anode. Purchase 2 end cap kits part number 130-5176. These end caps are fragile and may break when they are removed (photo below).
  6. The following is something that you should either do every 2-3 years: The exhaust manifold and/or exhaust elbow might be partially clogged with carbon. Remove the exhaust elbow and inspect it. You will probably be able to see inside the exhaust manifold. If carbon buildup is present in either, clean them.
Onan exhaust elbow and exhaust manifold in red circles. Required gaskets in the green circles:
image.png
image.png
image.png
image.png

CW Bill Rouse Amel Owners Yacht School
Address: 720 Winnie, Galveston Island, Texas 77550 
View My Training Calendar


On Sat, May 1, 2021 at 6:54 AM Slavko Despotovic <slavko@...> wrote:

Hi Bill,

I have a problem with generator overheating (106 dC) coolant temperature . Sea water exhaust temperature up to 80 dC. Have checked impeller (it is new) , new oil, fuel filters, new oil. Before service at 1000 hours it was working ok. I am thinking that thermostat might be a problem. Or should I concentrate on seawater cooling system?
question is if thermostat fails( it is open, no flow od coolant) is the seawater system strong enough to cool the engine on 80 dC? In my generator this is not the case.

thank you.


Slavko

SM 2000
#279 Bonne Anse in Portoroz


Slavko Despotovic
 

Hi Bill,

I have a problem with generator overheating (106 dC) coolant temperature . Sea water exhaust temperature up to 80 dC. Have checked impeller (it is new) , new oil, fuel filters, new oil. Before service at 1000 hours it was working ok. I am thinking that thermostat might be a problem. Or should I concentrate on seawater cooling system?
question is if thermostat fails( it is open, no flow od coolant) is the seawater system strong enough to cool the engine on 80 dC? In my generator this is not the case.

thank you.


Slavko

SM 2000
#279 Bonne Anse in Portoroz


 

Mark,

I think I should have suggested that because the exhaust elbow was at the correct temperature, but the engine overheating. 

I think if I added the following  to the top of the check list you would have found it earlier:

"Remove the exhaust elbow and inspect the junction of the elbow with the manifold. If you see carbon buildup, remove the manifold and clean or replace both the manifold and the elbow."

Agree?

Best,

CW Bill Rouse 
Amel Owners Yacht School
+1 832-380-4970 | brouse@...
720 Winnie, Galveston Island, Texas 77550 
www.AmelOwnersYachtSchool.com 
Yacht School Calendar: www.preparetocastoff.blogspot.com/p/calendar.html


   


On Fri, Aug 21, 2020, 5:19 PM Thomas Peacock <peacock8491@...> wrote:
Hi Mark,

I was actually going to suggest that you look at the exhaust manifold, but didn’t want to look dumb. However, our problem wasn’t that it would shut down, but that it would not start. Many $$$ later, a good mechanic looked there and found the culprit.

In addition, I would have thought that the exhaust temperature would have risen and tripped the generator; but not all Onans are the same, I don’t think we have an exhaust temperature monitor, just a water temp.

I should add that the exhaust manifold carbon buildup is a common problem; it results from the generator being run at relatively low power demand levels, never at high enough fuel consumption (the RPM are constant) to burn out the carbon.

Everyone who has an Onan should be aware of this, and keep an eye on the build-up.  Ours was so far gone that we had to replace the manifold, cleaning was not an option.

Tom Peacock
SM 240 Aletes
Chesapeake Bay

On Aug 21, 2020, at 5:48 PM, Mark Pitt <mark_pitt@...> wrote:

 After replacing the thermostat, water sensor, fan belt, coolant, and raw water pump, it turns out the problem was carbon buildup in the exhaust manifold.  That’s been cleaned out and a new exhaust elbow added and all seems good now.  Thanks to all for their suggestions.

Mark Pitt
Sabbatical III,SM#419
Nantucket


--
Tom Peacock
SM 240 Aletes
Chesapeake Bay


Thomas Peacock
 

Hi Mark,

I was actually going to suggest that you look at the exhaust manifold, but didn’t want to look dumb. However, our problem wasn’t that it would shut down, but that it would not start. Many $$$ later, a good mechanic looked there and found the culprit.

In addition, I would have thought that the exhaust temperature would have risen and tripped the generator; but not all Onans are the same, I don’t think we have an exhaust temperature monitor, just a water temp.

I should add that the exhaust manifold carbon buildup is a common problem; it results from the generator being run at relatively low power demand levels, never at high enough fuel consumption (the RPM are constant) to burn out the carbon.

Everyone who has an Onan should be aware of this, and keep an eye on the build-up.  Ours was so far gone that we had to replace the manifold, cleaning was not an option.

Tom Peacock
SM 240 Aletes
Chesapeake Bay

On Aug 21, 2020, at 5:48 PM, Mark Pitt <mark_pitt@...> wrote:

 After replacing the thermostat, water sensor, fan belt, coolant, and raw water pump, it turns out the problem was carbon buildup in the exhaust manifold.  That’s been cleaned out and a new exhaust elbow added and all seems good now.  Thanks to all for their suggestions.

Mark Pitt
Sabbatical III,SM#419
Nantucket


--
Tom Peacock
SM 240 Aletes
Chesapeake Bay


Mark Pitt
 

 After replacing the thermostat, water sensor, fan belt, coolant, and raw water pump, it turns out the problem was carbon buildup in the exhaust manifold.  That’s been cleaned out and a new exhaust elbow added and all seems good now.  Thanks to all for their suggestions.

Mark Pitt
Sabbatical III,SM#419
Nantucket


 

Mark,

Guessing from thousands of miles away.

The shutdown is because the block is too hot. 

Normally it should be about 80C under load and warmed up. However, the exhaust elbow is at the correct temperature. My guess is that the coolant is not circulating as it should, and therefore not cooling the block. The seawater side seems to be functioning correctly, but not the coolant side. That could be a number of things including the coolant (captive) pump, a loose fan belt on the captive pump, a stuck thermostat, an obstruction somewhere in the coolant path.

I would start with the thermostat. If you do not have a spare, you can temporarily remove it until you have one. You will likely need some PermaTex-type gasket material because those gaskets usually tear.

Bill
CW Bill Rouse Amel Owners Yacht School
Address: 720 Winnie, Galveston Island, Texas 77550 
View My Training Calendar


On Fri, Aug 14, 2020 at 1:28 PM Mark Pitt <mark_pitt@...> wrote:
I installed a new flow sensor that I had in my spares.  I also replaced the impeller.  The existing impeller did not look too bad but it appeared that one vane had adhered to the impeller hub, perhaps from overheating.  I opened the cooler and found no obstructions. I also examined the hose segments from the raw water pump to the cooler and found no obstructions.

I then ran the generator under a load of 13.5 amp.  When the engine block temperature reached 103C degrees, I shut the generator off.  The exhaust elbow never topped 52C degrees.  So this appears to be a problem on the cooling side.  The cooler itself is a less than two year old "Mr. Cool" that has been in service for at least 600 hours without problem. When I put the boat away for the winter last October, there was no hint of problem.  I fully winterized it at the time.

Suggestions?

Mark Pitt
Sabbatical III, SM #419, Rhode Island, USA


Elja Röllinghoff Balu SM 222
 

He Mark



i've seen it once the Impeller didn't hold on the wave.

The level on the wave of the water pump that fixes the impeller and turns it was weared , so the impeller was in good condition but not worked because it slipped through the wave .
Good luck
Elja
SM Balu 222

Von meinem iPhone gesendet


Mark Pitt
 

I installed a new flow sensor that I had in my spares.  I also replaced the impeller.  The existing impeller did not look too bad but it appeared that one vane had adhered to the impeller hub, perhaps from overheating.  I opened the cooler and found no obstructions. I also examined the hose segments from the raw water pump to the cooler and found no obstructions.

I then ran the generator under a load of 13.5 amp.  When the engine block temperature reached 103C degrees, I shut the generator off.  The exhaust elbow never topped 52C degrees.  So this appears to be a problem on the cooling side.  The cooler itself is a less than two year old "Mr. Cool" that has been in service for at least 600 hours without problem. When I put the boat away for the winter last October, there was no hint of problem.  I fully winterized it at the time.

Suggestions?

Mark Pitt
Sabbatical III, SM #419, Rhode Island, USA


Thomas Kleman
 

Impeccable timing on your circumnav- we are stuck in Hawaii now waiting......had a new shutdown just last night. The AC water pump capacitor caused a genset shutdown at what should have been about 3 KW.....and gave me the wrong code as well. Please post when you discover the solution. I'm sure this will happen to us.

Tom and Kirstin
SM 2K 422
L'ORIENT
Hanalei Bay, Kauia


Mark Pitt
 

Hi Tom and Kirstin,

I also have had at least a dozen shutdowns in the 17 years that I have owned Sabbatical III and in every case there was a shutdown code, including shutdowns due to a faulty sensor.  So this is a new one for me.

Having a spare central board is a good idea, although now that our circumnavigation is done, not as crucial.  I heard that they are quite expensive.  My wife and I are only summer livesboards now.

Mark Pitt
SV Sabbatical III, SM419, Rhode Island


On Aug 13, 2020, at 1:09 PM, Thomas Kleman <lorient422@...> wrote:

Hey Mark- your post caught my eye because we are hull #422....,Bill's approach (eliminate sensors one by one) is what we do on L'ORIENT. I'm troubled by the lack of a diagnostic code, though. We've probably had 15-20 genset shutdowns in the 10 years we've owned the boat; never was there no code. Since it's really easy, at some point I'd swap out the central board (if you have one). I think this is a vital spare part to have on a SM because of how much you depend on 220 v (unless you've done a major lithium conversion).

Tom and Kirstin
SM 2K 422
Hanalei Bay, Kauia