I hope there is still here someone experienced with this old type of engine so it can give me some light on my problem.
I have rebuilt this engine (Cummins V-504-M 195HP/3000RPM) and it serves me very well. Now I have about 135 hours of operation. Thing is that I am not driving it hard, most of time I drive it around 1500RPM. After rebuild, engine worked spotlessly in whole range of RPM with no smoke at all (everything new in engine and done by Cummins professional). Since I have not been driving it fast because of fuel consumption and my needs, I have just recently tried to go on speed again and above 2300RPM engine starts to smoke in purple/blue, has loss of power and distinctive smell. That RPM is about when my semi displacement boat is starting to transit from displacement to planning (heavy load). Above that RPM the engine can achieve maximum RPM, but lacks power. Under that RPM, engine works perfectly without any smoke or smell.
I know that blue smoke is probably oil, but I cannot confirm that since under that RPM engine does not consume any oil (level unchanged on dipstick) and I do not want to drive it above that just to check that, because I could maybe make more harm to engine. Oil pressure is fine, as always from the beginning (40psi to 80psi).
I had one failure on one summer trip, which could be the culprit, but I do not know if that is exactly when it started since I did not drive it fast until now. And on my running RPM I have not spotted any change. What happened then is that hose between engine and "distant" oil filter element was badly crimped probably and therefore bursted on the connection letting the engine to discharge all the oil in engine room. Luckily, Kysor alarm spotted low oil pressure and turned off the engine. Unluckily, although I have seen the exact alarm and what happend on pressure instrument, it was bad location for that to happen and I had to turn on the engine for 10 more seconds to stop the boat not to hit something because of big inertia before I have dropped the anchor. It was safety vs engine and it was critical, so I did what I did. Kysor has let me just about 8 seconds this time, just enough to change the outcome. Just before Kysor has turned off the engine, I had some strange sound, like grinding, but I have never had engine turning off with gear in reverse (Borg Warner 72), so it could be from engine, it could be from gearbox, could be anything really, although I have thought about the worst at that moment - engine itself.
After towing the boat to the shore, I have made a new hose and changed the oil. It was left only about 3 or 4 liters of oil in the engine out of 18 or 19 liters needed for engine operation. Actually engine needs maybe 2 or 3 liters less than that, since whenever I put all to the HIGH level on the dipstick it consumes it. Then, I have just left it to use the oil and see if it is going to stop and when it comes approximately a bit lower than the middle of HIGH and LOW mark it stops and stays there forever, so I always use that level of oil. After changed oil and hose, I have disconnected the fuel shut off valve and cranked the engine to achieve oil pressure before firing it up. Then I have reconnected the fuel shut off valve wire and fired up the engine. It worked flawlessly as nothing has ever happend, no smoke, no strange sounds, nothing. But I have continued driving it on my cruising RPM, haven't tested higher RPMs, so I do not know if that is when the problem showed up.
That problem has happend at 50 working hours (about the same as with my first oil change, recommended by rebuilder since engine is "new" and the following intervals to be at 100 hours), since then I have changed the oil again at exactly 100 hours and plan to change it every following 100 hours. Never spotted any problem until trying to reach speed recently.
Since I have instantly remembered the event with hose, I thought of blowby. I have opened the oil pouring plug with warmed up engine and at idle and there is air blowing and constant thin (I would say maybe white/gray, but more like white) smoke (not doing choo choo, just constant), but I cannot compare it to anything since I have never opened it like that before. It is not the blow that would lunch the plug in the air, it is just that I can feel it blowing on my hand and when I just put the plug on it without tightening it up, it stays there, it dances maybe a bit if I lift it with hand and release the blow around it, but that old metal plug is heavier than those plastic ones on new engines that I have seen on the youtube videos.
So can anyone tell me is there a possibility that it is just the case of maybe problem with valves and valve stems or injectors before thinking about piston rings and cylinder walls so I know what to expect before calling the rebuilder? Or you would lean more towards the rings and blowby?
Sorry for the long post, but thought I will get better answers if I describe it better.
Thank you in advance.
I have rebuilt this engine (Cummins V-504-M 195HP/3000RPM) and it serves me very well. Now I have about 135 hours of operation. Thing is that I am not driving it hard, most of time I drive it around 1500RPM. After rebuild, engine worked spotlessly in whole range of RPM with no smoke at all (everything new in engine and done by Cummins professional). Since I have not been driving it fast because of fuel consumption and my needs, I have just recently tried to go on speed again and above 2300RPM engine starts to smoke in purple/blue, has loss of power and distinctive smell. That RPM is about when my semi displacement boat is starting to transit from displacement to planning (heavy load). Above that RPM the engine can achieve maximum RPM, but lacks power. Under that RPM, engine works perfectly without any smoke or smell.
I know that blue smoke is probably oil, but I cannot confirm that since under that RPM engine does not consume any oil (level unchanged on dipstick) and I do not want to drive it above that just to check that, because I could maybe make more harm to engine. Oil pressure is fine, as always from the beginning (40psi to 80psi).
I had one failure on one summer trip, which could be the culprit, but I do not know if that is exactly when it started since I did not drive it fast until now. And on my running RPM I have not spotted any change. What happened then is that hose between engine and "distant" oil filter element was badly crimped probably and therefore bursted on the connection letting the engine to discharge all the oil in engine room. Luckily, Kysor alarm spotted low oil pressure and turned off the engine. Unluckily, although I have seen the exact alarm and what happend on pressure instrument, it was bad location for that to happen and I had to turn on the engine for 10 more seconds to stop the boat not to hit something because of big inertia before I have dropped the anchor. It was safety vs engine and it was critical, so I did what I did. Kysor has let me just about 8 seconds this time, just enough to change the outcome. Just before Kysor has turned off the engine, I had some strange sound, like grinding, but I have never had engine turning off with gear in reverse (Borg Warner 72), so it could be from engine, it could be from gearbox, could be anything really, although I have thought about the worst at that moment - engine itself.
After towing the boat to the shore, I have made a new hose and changed the oil. It was left only about 3 or 4 liters of oil in the engine out of 18 or 19 liters needed for engine operation. Actually engine needs maybe 2 or 3 liters less than that, since whenever I put all to the HIGH level on the dipstick it consumes it. Then, I have just left it to use the oil and see if it is going to stop and when it comes approximately a bit lower than the middle of HIGH and LOW mark it stops and stays there forever, so I always use that level of oil. After changed oil and hose, I have disconnected the fuel shut off valve and cranked the engine to achieve oil pressure before firing it up. Then I have reconnected the fuel shut off valve wire and fired up the engine. It worked flawlessly as nothing has ever happend, no smoke, no strange sounds, nothing. But I have continued driving it on my cruising RPM, haven't tested higher RPMs, so I do not know if that is when the problem showed up.
That problem has happend at 50 working hours (about the same as with my first oil change, recommended by rebuilder since engine is "new" and the following intervals to be at 100 hours), since then I have changed the oil again at exactly 100 hours and plan to change it every following 100 hours. Never spotted any problem until trying to reach speed recently.
Since I have instantly remembered the event with hose, I thought of blowby. I have opened the oil pouring plug with warmed up engine and at idle and there is air blowing and constant thin (I would say maybe white/gray, but more like white) smoke (not doing choo choo, just constant), but I cannot compare it to anything since I have never opened it like that before. It is not the blow that would lunch the plug in the air, it is just that I can feel it blowing on my hand and when I just put the plug on it without tightening it up, it stays there, it dances maybe a bit if I lift it with hand and release the blow around it, but that old metal plug is heavier than those plastic ones on new engines that I have seen on the youtube videos.
So can anyone tell me is there a possibility that it is just the case of maybe problem with valves and valve stems or injectors before thinking about piston rings and cylinder walls so I know what to expect before calling the rebuilder? Or you would lean more towards the rings and blowby?
Sorry for the long post, but thought I will get better answers if I describe it better.
Thank you in advance.