heavyhauler Posted July 20, 2008 Share Posted July 20, 2008 A friend has a 1950 LJSW and it has not been run very much-mostly idling. We were moving some other equipment in the garage last week and left the LJ idling some distance outside from the door. When we got around to it, the engine was missing on one cylinder and raw fuel was leaking from the bottom of the exhaust. We tried to get the temperature up by driving it to see if perhaps the accumulated carbon may have blocked something. That did not help and I am puzzled as to what happened. There is no fuel in the oil but I'm not sure that rules out a cracked piston. Perhaps a stuck exhaust valve might be the culprit? The 190 Cummins has been well maintained and only has 103,000 miles on it but it has not been run up to operating temperature for years. When it has been moved and left running, it has run very well but not for long periods of time. Any suggestions before we start tearing it down would be most appreciated.Best regards,John Quote Link to comment https://www.bigmacktrucks.com/topic/4022-fuel-in-the-exhaust/ Share on other sites More sharing options...
Rob Posted July 20, 2008 Share Posted July 20, 2008 You probably need to get it much hotter than it has seen in years. Can you drive with the brakes lightly dragging for short periods of time? I "hitched" my Mack tractor that had not seen a load in several years to a large field harrow and dragged it around a field for over an hour and it worked wonders on the engine. It did crack the radiator though!I think your problem is related to the fuel and probably not mechanical that won't sef correct with working the engine.Rob Quote Plodding along with no job nor practical application for my existence, but still trying to fix what's broke. Link to comment https://www.bigmacktrucks.com/topic/4022-fuel-in-the-exhaust/#findComment-20735 Share on other sites More sharing options...
heavyhauler Posted July 20, 2008 Author Share Posted July 20, 2008 You probably need to get it much hotter than it has seen in years. Can you drive with the brakes lightly dragging for short periods of time? I "hitched" my Mack tractor that had not seen a load in several years to a large field harrow and dragged it around a field for over an hour and it worked wonders on the engine. It did crack the radiator though!I think your problem is related to the fuel and probably not mechanical that won't sef correct with working the engine.RobRob: We tried to drive it for about 15 minutes but it did not seem to help. She was blowing lots of smoke and fuel was running out the bottom of the exhaust stack probably because that one cylinder was not firing. Thanks for your help.Regards,John Quote Link to comment https://www.bigmacktrucks.com/topic/4022-fuel-in-the-exhaust/#findComment-20738 Share on other sites More sharing options...
vanscottbuilders Posted July 20, 2008 Share Posted July 20, 2008 John,The fuel problem could be a number of things, but the hunch that an exhaust valve may be stuck, or worse, broken, is probably not a bad idea. Likely a valve spring, if anything is truly amiss. I agree with Rob in that the truck could use some fairly close monitored running to get "some heat in the exhaust".This might mean a loaded condition for an hour or more at working RPM's.Have you checked for any unusual noise from a stethoscope through the valve train?I drove over Grand Island last week, and somehow missed the big green Mack. Thought for sure itwould be out on the streets.Let us know how you make out with the Cummins.Paul Van Scott Quote Link to comment https://www.bigmacktrucks.com/topic/4022-fuel-in-the-exhaust/#findComment-20740 Share on other sites More sharing options...
theakerstwo Posted July 20, 2008 Share Posted July 20, 2008 You already think it is on one cylinder so chack it out. pull valve cover and run the over head on that cylinder first and note where your torque wrench starts to torque. it should not start to move at leass than 60 inches on the inche meter. if it is loose then pull the adjusting screw and remove the push tube and with a hook on a coat hanger you can lift the roller and look at and if it has a scroreing on the roller or pitts then the cam will be bad. that will leve the injector lose and cause it to over fuel but not pop fuel in like it should and will cause bad smoke. this is common. A cracked injector cup will do the same thing. Low compression on that clyinder will do that but check to injector adjustment first. Those engines need the over head set more often then people think. Quote glenn akers Link to comment https://www.bigmacktrucks.com/topic/4022-fuel-in-the-exhaust/#findComment-20743 Share on other sites More sharing options...
Rob Posted July 20, 2008 Share Posted July 20, 2008 Rob:We tried to drive it for about 15 minutes but it did not seem to help. She was blowing lots of smoke and fuel was running out the bottom of the exhaust stack probably because that one cylinder was not firing. Thanks for your help.Regards,JohnI completely missed the part where you mentioned it was a Cummins engine. Off the top of my head I thought the engine was an END510, with Lanova combustion chambers. I agree with Glenn's suggestion as the overheads did need run quite often on the older Cummins engines.Rob Quote Plodding along with no job nor practical application for my existence, but still trying to fix what's broke. Link to comment https://www.bigmacktrucks.com/topic/4022-fuel-in-the-exhaust/#findComment-20745 Share on other sites More sharing options...
heavyhauler Posted July 20, 2008 Author Share Posted July 20, 2008 I completely missed the part where you mentioned it was a Cummins engine. Off the top of my head I thought the engine was an END510, with Lanova combustion chambers. I agree with Glenn's suggestion as the overheads did need run quite often on the older Cummins engines.RobRob and Glenn: No unusual noise but we'll definitely look at those overheads to start. I'll keep you posted.Regards,John Quote Link to comment https://www.bigmacktrucks.com/topic/4022-fuel-in-the-exhaust/#findComment-20747 Share on other sites More sharing options...
fifth wheel Posted July 21, 2008 Share Posted July 21, 2008 A friend has a 1950 LJSW and it has not been run very much-mostly idling. We were moving some other equipment in the garage last week and left the LJ idling some distance outside from the door. When we got around to it, the engine was missing on one cylinder and raw fuel was leaking from the bottom of the exhaust. We tried to get the temperature up by driving it to see if perhaps the accumulated carbon may have blocked something. That did not help and I am puzzled as to what happened. There is no fuel in the oil but I'm not sure that rules out a cracked piston. Perhaps a stuck exhaust valve might be the culprit? The 190 Cummins has been well maintained and only has 103,000 miles on it but it has not been run up to operating temperature for years. When it has been moved and left running, it has run very well but not for long periods of time. Any suggestions before we start tearing it down would be most appreciated.Best regards,JohnYou have sticking plunger you can unstick without removing the injector, but if it is scored it will stick again. You are going to have a very serious problem if raw fuel drips into the cylinder and you crank the engine, use the compression release. I wouldn't do anything else without first checking the injector.fifth wheel Quote Link to comment https://www.bigmacktrucks.com/topic/4022-fuel-in-the-exhaust/#findComment-20757 Share on other sites More sharing options...
Bollweevil Posted July 21, 2008 Share Posted July 21, 2008 Normally, the overhead adjustment will change over time due to wear. Changes over night are not usually considered normal. Especially a change like this. If you have white smoke, you have compression. You can isolate the weak, or dead cylinder with an infrared heat gun. If you don't have one available, after running the engine for a short time, feel of the cyl. heads at the exhaust ports. try to find a cold one. Many times a slobbering cylinder will leak out of the offending exhaust port and run down the block. If you still haven't found it pull the manifold off the engine and start it up. The bad cylinder will look like a volcano. How ever you isolate the dead cylinder, find it first before touching the overhead. Your engine should set by the outer base circle method as the later STC engines. After years of NTC's with Top Stop injectors, we are doing it the old way again. Once you have the bad cylinder at TDC on it's compression stroke, and you can't see something loose, bent, or broken. Then pull the injector. my guess is that the tip is gone off of it. Quote Link to comment https://www.bigmacktrucks.com/topic/4022-fuel-in-the-exhaust/#findComment-20759 Share on other sites More sharing options...
heavyhauler Posted July 21, 2008 Author Share Posted July 21, 2008 Normally, the overhead adjustment will change over time due to wear. Changes over night are not usually considered normal. Especially a change like this. If you have white smoke, you have compression. You can isolate the weak, or dead cylinder with an infrared heat gun. If you don't have one available, after running the engine for a short time, feel of the cyl. heads at the exhaust ports. try to find a cold one. Many times a slobbering cylinder will leak out of the offending exhaust port and run down the block. If you still haven't found it pull the manifold off the engine and start it up. The bad cylinder will look like a volcano. How ever you isolate the dead cylinder, find it first before touching the overhead. Your engine should set by the outer base circle method as the later STC engines. After years of NTC's with Top Stop injectors, we are doing it the old way again. Once you have the bad cylinder at TDC on it's compression stroke, and you can't see something loose, bent, or broken. Then pull the injector. my guess is that the tip is gone off of it.Thank you for all those suggestions. I have posted a few photos in the member's gallery if you'd like to see the truck. Best regards,John Quote Link to comment https://www.bigmacktrucks.com/topic/4022-fuel-in-the-exhaust/#findComment-20776 Share on other sites More sharing options...
heavyhauler Posted August 22, 2008 Author Share Posted August 22, 2008 Thank you for all those suggestions. I have posted a few photos in the member's gallery if you'd like to see the truck. Best regards,JohnAccording to Matt Pfahl whose shop is getting the truck ready for Roger Gerhards show in Lititz, PA in early October, this Cummins engine has 3 head gaskets and the gasket for cylinders 5 and 6 was blown allowing raw fuel to be exchanged between the 2 pistons. Fuel got past the rings and into the oil pan. The bearings seem to be OK but we'll know more in a week. I have posted more photos of the truck plus photos of the original operator's manual. Quote Link to comment https://www.bigmacktrucks.com/topic/4022-fuel-in-the-exhaust/#findComment-21505 Share on other sites More sharing options...
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