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#1
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Diesel troubleshooting
I have 2 Cummins 6bt5.7M (4k hours) that are beginning to smoke and
leave a film at the exhaust (sea water output). The port engine is the worst, but both engines have the same problem. In trying to identify the problem I've preformed the following test. 1) no (or very little) oil usage. 2) Both Engines run at 180 deg. 3) Turbo output 2600rpm (port)16psi (starb) 18psi Cummins manual calls for 20-25psi. No intake obstructions. No leaks detected any place from output of turbo up to and including the intake manifold. No detectable leaks in exhaust. No restrictions in oil return line. 4) Turbo (Holset H1C) compressor impeller can be pushed to contact the housing. (I would guess .100" movement) Holset calls for .012" - ..018" radial movement 5) Turbo axial movement .010 both sides. Holset calls for .025. 6) Blowby (taken with the Cummins recommend setup using calibrated 0-100"h20 gauge with dipstick hole blocked). at 1000rpm approx. 2" (both engines) but at 2600 rpm 0". (I've ordered a diesel compression tester hope to have it next weekend while I'm testing the compression, I'll get the injectors tested) These are the steps that I've taken so far. The most glaring result to me is the blowby. There is none detected at rated speed. I've talked to the Cummins dealer, he says that it can't be and recommend using a manometer instead of the gauge. The turbo's are bad according to the holset manual so I pulled them and brought them to be rebuilt (holset authorized). The mechanic looked at them when I dropped them off and While he didn't come out and say so, I got the impression that he thought they were ok. He will be taking them apart this week. OK, now for my diagnosis; The smoke and sheen that I see are unburned diesel. The cause is low turbo pressure not getting enough air into the cylinders. The low turbo pressure is Caused by bad oil seals in the turbos allowing crankcase pressure to be reduced by the vacuum of the turbo compressor. The question of why would both engines have the same problem comes up. My theory is; when changing fuel filters, I use starting fluid to get the fuel to start. The ether (or other chemicals in the starting fluid) has caused the seal to deteriorate. Anyone have any feedback? The engines are honey's. They have never failed in the 10 years we've owned the boat ( 3000hrs). The smoke is not a killer yet, but I would like to solve the problem before it gets worse. Thanking anyone in advance for advice, criticism or observations. Mike |
#2
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Diesel troubleshooting
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#3
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Diesel troubleshooting
Subject: Diesel troubleshooting
From: (Mike) Try this site. http://boatdiesel.com/Forums/Forums.cfm Capt. Bill |
#4
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Diesel troubleshooting
Mike wrote:
I have 2 Cummins 6bt5.7M (4k hours) that are beginning to smoke and leave a film at the exhaust (sea water output). The port engine is the worst, but both engines have the same problem. The low turbo pressure & excessive radial movement is definitely a problem. New bearings? Good idea to get the injectors checked out too, though. FWIW I have a problem with a small diesel genset. I have rebuilt the fuel supply system, and the engine ran fine unloaded, but after a while started to bog down and then died. Sounds like a fuel restriction? Anyway I did not have time to troubleshoot it this past weekend, maybe next. Fair Skies Doug King |
#5
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Diesel troubleshooting
On Mon, 08 Mar 2004 11:33:36 -0500, DSK wrote:
Mike wrote: I have 2 Cummins 6bt5.7M (4k hours) that are beginning to smoke and leave a film at the exhaust (sea water output). The port engine is the worst, but both engines have the same problem. The low turbo pressure & excessive radial movement is definitely a problem. New bearings? Good idea to get the injectors checked out too, though. FWIW I have a problem with a small diesel genset. I have rebuilt the fuel supply system, and the engine ran fine unloaded, but after a while started to bog down and then died. Sounds like a fuel restriction? Anyway I did not have time to troubleshoot it this past weekend, maybe next. Is your generator a Kubota three cylinder? I had this exact same problem last year with the one here at the house and it was crap in the fuel tank and line - sludge actually. Later, Tom S. Woodstock, CT ----------- "Do fishermen eat avocados? This is a question that no one ever thinks to ask." Russel Chatham, "Dark Waters" (1988) |
#6
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Diesel troubleshooting
I don't think I can give you any advice but I just have a question. I've
driven trucks all my life and by your post you say the problem might be unburnt fuel. That's what puzzles me. Every diesel I've driven always have a return line to the tank for unburnt fuel. Please forgive me if I completely ignorant on marine diesels but why would they not have a return line? I can tell you that the little amount of either that you used would not hurt anything. What kind of outside temps has your fuel been in? And how long has the diesel been in the tank? Have you switched fuel. Did you burn #1 or #2 diesel. Is it low sulfur diesel? I ask these questions because 4K hours to me is not a whole lot of hours. "Mike" wrote in message om... I have 2 Cummins 6bt5.7M (4k hours) that are beginning to smoke and leave a film at the exhaust (sea water output). The port engine is the worst, but both engines have the same problem. In trying to identify the problem I've preformed the following test. 1) no (or very little) oil usage. 2) Both Engines run at 180 deg. 3) Turbo output 2600rpm (port)16psi (starb) 18psi Cummins manual calls for 20-25psi. No intake obstructions. No leaks detected any place from output of turbo up to and including the intake manifold. No detectable leaks in exhaust. No restrictions in oil return line. 4) Turbo (Holset H1C) compressor impeller can be pushed to contact the housing. (I would guess .100" movement) Holset calls for .012" - .018" radial movement 5) Turbo axial movement .010 both sides. Holset calls for .025. 6) Blowby (taken with the Cummins recommend setup using calibrated 0-100"h20 gauge with dipstick hole blocked). at 1000rpm approx. 2" (both engines) but at 2600 rpm 0". (I've ordered a diesel compression tester hope to have it next weekend while I'm testing the compression, I'll get the injectors tested) These are the steps that I've taken so far. The most glaring result to me is the blowby. There is none detected at rated speed. I've talked to the Cummins dealer, he says that it can't be and recommend using a manometer instead of the gauge. The turbo's are bad according to the holset manual so I pulled them and brought them to be rebuilt (holset authorized). The mechanic looked at them when I dropped them off and While he didn't come out and say so, I got the impression that he thought they were ok. He will be taking them apart this week. OK, now for my diagnosis; The smoke and sheen that I see are unburned diesel. The cause is low turbo pressure not getting enough air into the cylinders. The low turbo pressure is Caused by bad oil seals in the turbos allowing crankcase pressure to be reduced by the vacuum of the turbo compressor. The question of why would both engines have the same problem comes up. My theory is; when changing fuel filters, I use starting fluid to get the fuel to start. The ether (or other chemicals in the starting fluid) has caused the seal to deteriorate. Anyone have any feedback? The engines are honey's. They have never failed in the 10 years we've owned the boat ( 3000hrs). The smoke is not a killer yet, but I would like to solve the problem before it gets worse. Thanking anyone in advance for advice, criticism or observations. Mike |
#7
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Diesel troubleshooting
Excess fuel to the pumps goes to the return line. Unburnt fuel is fuel that
was injected and did not burn. Bad injector that does not atomize the fuel well, or injects too much fuel allows the fuel to not get burnt, and comes out the exhaust. Diesel semi's that are blowing black smoke are ejecting unburnt fuel. Bill "Dave R" wrote in message ... I don't think I can give you any advice but I just have a question. I've driven trucks all my life and by your post you say the problem might be unburnt fuel. That's what puzzles me. Every diesel I've driven always have a return line to the tank for unburnt fuel. Please forgive me if I completely ignorant on marine diesels but why would they not have a return line? I can tell you that the little amount of either that you used would not hurt anything. What kind of outside temps has your fuel been in? And how long has the diesel been in the tank? Have you switched fuel. Did you burn #1 or #2 diesel. Is it low sulfur diesel? I ask these questions because 4K hours to me is not a whole lot of hours. "Mike" wrote in message om... I have 2 Cummins 6bt5.7M (4k hours) that are beginning to smoke and leave a film at the exhaust (sea water output). The port engine is the worst, but both engines have the same problem. In trying to identify the problem I've preformed the following test. 1) no (or very little) oil usage. 2) Both Engines run at 180 deg. 3) Turbo output 2600rpm (port)16psi (starb) 18psi Cummins manual calls for 20-25psi. No intake obstructions. No leaks detected any place from output of turbo up to and including the intake manifold. No detectable leaks in exhaust. No restrictions in oil return line. 4) Turbo (Holset H1C) compressor impeller can be pushed to contact the housing. (I would guess .100" movement) Holset calls for .012" - .018" radial movement 5) Turbo axial movement .010 both sides. Holset calls for .025. 6) Blowby (taken with the Cummins recommend setup using calibrated 0-100"h20 gauge with dipstick hole blocked). at 1000rpm approx. 2" (both engines) but at 2600 rpm 0". (I've ordered a diesel compression tester hope to have it next weekend while I'm testing the compression, I'll get the injectors tested) These are the steps that I've taken so far. The most glaring result to me is the blowby. There is none detected at rated speed. I've talked to the Cummins dealer, he says that it can't be and recommend using a manometer instead of the gauge. The turbo's are bad according to the holset manual so I pulled them and brought them to be rebuilt (holset authorized). The mechanic looked at them when I dropped them off and While he didn't come out and say so, I got the impression that he thought they were ok. He will be taking them apart this week. OK, now for my diagnosis; The smoke and sheen that I see are unburned diesel. The cause is low turbo pressure not getting enough air into the cylinders. The low turbo pressure is Caused by bad oil seals in the turbos allowing crankcase pressure to be reduced by the vacuum of the turbo compressor. The question of why would both engines have the same problem comes up. My theory is; when changing fuel filters, I use starting fluid to get the fuel to start. The ether (or other chemicals in the starting fluid) has caused the seal to deteriorate. Anyone have any feedback? The engines are honey's. They have never failed in the 10 years we've owned the boat ( 3000hrs). The smoke is not a killer yet, but I would like to solve the problem before it gets worse. Thanking anyone in advance for advice, criticism or observations. Mike |
#8
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Diesel troubleshooting
"Mike" wrote in message I have 2 Cummins 6bt5.7M (4k hours) that are beginning to smoke and leave a film at the exhaust (sea water output). Is this at all speeds, or only under wide open throttle? (okay, diesels aren't throttled, but I never picked up what the proper term for a diesel is....). If it is WOT only, is this slick so obvious you can see it going full speed? Other than the oil in the water, how are the engines running? Still giving you the same performace as before? How about fuel usage? 3) Turbo output 2600rpm (port)16psi (starb) 18psi Cummins manual calls for 20-25psi. Is this measurement taken while under load, or while in neutral? I wouldn't expect the turbos to be working very hard unless the engines were heavily loaded. Engine RPM does not indicate turbo RPM. OK, now for my diagnosis; The smoke and sheen that I see are unburned diesel. Probably. The cause is low turbo pressure not getting enough air into the cylinders. Only if this problem is occuring at or near WOT conditions. If this problem happens at idle speeds (which is when I would expect you would be able to see the sheen in your wake) then it isn't the turbo. The low turbo pressure is Caused by bad oil seals in the turbos allowing crankcase pressure to be reduced by the vacuum of the turbo compressor. I don't follow you here. If there aren't any obstructions in the turbo intake (like an air filter) then there shouldn't be much vacuum generated. I am not familiar with this engine at all, so I don't understand how the crankcase pressure and turbo are related (the turbos I am familiar with have been mounted external to the engine and don't have any connection to the crankcase that could leak). If the problem were bad oil seals, however, then I would expect that there would be a loss of oil. If the leak went external then it should be making a mess in the engine room. If the leak went internal then I would expect it to just be burned, only showing up in the fact that you have to add oil often. Anyone have any feedback? The engines are honey's. They have never failed in the 10 years we've owned the boat ( 3000hrs). The smoke is not a killer yet, but I would like to solve the problem before it gets worse. When was the last time you had the injectors serviced? A diesel engine requires a little bit more than just squirting the fuel into the cylinder. Part of the injectors job is to atomize the fuel as it is injected so that it can burn. Vaporized fuel will ignite and burn. Liquid fuel will NOT burn. A worn injector can allow a portion of the fuel to enter as a liquid stream. Some of this will boil and burn, but portions of it will remain liquid, not burn and then go out the exhaust, causing your problem. The last time I had injectors serviced it cost me $125 an injector. I took them off, brought them down to a shop that specializes in diesel fuel systems. They had them about a day and then I picked them up and put them back on. An engine I was about ready to throw the towel in on ran great after that. If your injectors have 3000 hours on them, then I wouldn't hesitate to have them serviced. Rod |
#9
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Diesel troubleshooting
If the engines are turbo intercooled it might be that the intercooler is
partially blocked the induction air is too hot and has of low density giving incomplete combustion Good Luck!! Steve "Mike" wrote in message om... I have 2 Cummins 6bt5.7M (4k hours) that are beginning to smoke and leave a film at the exhaust (sea water output). The port engine is the worst, but both engines have the same problem. In trying to identify the problem I've preformed the following test. 1) no (or very little) oil usage. 2) Both Engines run at 180 deg. 3) Turbo output 2600rpm (port)16psi (starb) 18psi Cummins manual calls for 20-25psi. No intake obstructions. No leaks detected any place from output of turbo up to and including the intake manifold. No detectable leaks in exhaust. No restrictions in oil return line. 4) Turbo (Holset H1C) compressor impeller can be pushed to contact the housing. (I would guess .100" movement) Holset calls for .012" - .018" radial movement 5) Turbo axial movement .010 both sides. Holset calls for .025. 6) Blowby (taken with the Cummins recommend setup using calibrated 0-100"h20 gauge with dipstick hole blocked). at 1000rpm approx. 2" (both engines) but at 2600 rpm 0". (I've ordered a diesel compression tester hope to have it next weekend while I'm testing the compression, I'll get the injectors tested) These are the steps that I've taken so far. The most glaring result to me is the blowby. There is none detected at rated speed. I've talked to the Cummins dealer, he says that it can't be and recommend using a manometer instead of the gauge. The turbo's are bad according to the holset manual so I pulled them and brought them to be rebuilt (holset authorized). The mechanic looked at them when I dropped them off and While he didn't come out and say so, I got the impression that he thought they were ok. He will be taking them apart this week. OK, now for my diagnosis; The smoke and sheen that I see are unburned diesel. The cause is low turbo pressure not getting enough air into the cylinders. The low turbo pressure is Caused by bad oil seals in the turbos allowing crankcase pressure to be reduced by the vacuum of the turbo compressor. The question of why would both engines have the same problem comes up. My theory is; when changing fuel filters, I use starting fluid to get the fuel to start. The ether (or other chemicals in the starting fluid) has caused the seal to deteriorate. Anyone have any feedback? The engines are honey's. They have never failed in the 10 years we've owned the boat ( 3000hrs). The smoke is not a killer yet, but I would like to solve the problem before it gets worse. Thanking anyone in advance for advice, criticism or observations. Mike |
#10
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Diesel troubleshooting
If you really wish to get inteligent answers, you may want to try
rec.boats.cruising. It's a moderated group with boaters. No O.T. posts. |
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