Southern Krawler
Member
- 43
- 3
- 8
- Location
- El Paso,Tx
Hello everyone,
I purchased my first 5 ton about a month ago and finally got around to tinkering with it today . Its a 1983 m923 with a Cummins NHC 250. I bought the truck from a volunteer fire department in Oklahoma. The truck was advertised as "running and driving but has engine knocks and needs work." I decided that for the price it was worth the gamble and bought it. My initial impression after taking delivery of my new truck was that it was very straight and overall seemed like a solid truck. (Big thanks to 98G for the transportation! Great guy to deal with.) Needless to say I was extremely excited and happy with my new truck! I fired the truck up and immediately heard the pronounced knocking sound described by the seller. I gave the engine a little throttle to see if the knock got louder and it seemed to lessen as RPM's increased. I then attempted to move the truck into my yard and with the truck in gear the engine died as soon as I touched the throttle pedal. I attempted to restart it and it just cranked and cranked didn't even attempt to pop or start. I let the truck sit for about 5 minutes and then tried to start it again, to my surprise it fired right up. I rapidly moved it to the backyard and parked it. I pulled it out today to see what i could figure out and so far im not finding anything obvious. The Oil looks good no shiny specs or metallic pieces that I can see on the dipstick, in the rocker boxes, or from the small sample I removed from the oil pan. No oil in coolant or coolant in oil . Coolant level and oil levels are good. I used an infrared thermometer to measure the exhaust ports coming out of the heads and all were close to 190° at idle except cyl. #5 which was about 210°. I pulled the valve covers to see if i could see anything obvious but everything appears ok at first glance.
I then attempted to do a cylinder cutout test by holding open the injector rocker with a pry bar, but my results were inconsistent. Sometimes the engine would change rpm or sound slightly different but very indistinctly, nothing like pulling a sparkplug on a gas engine or doing a cylinder cutout test on a computer controlled diesel. Other times I got no reaction at all when the injectors were held closed and not one single injector responded consistently when doing this? I pulled the fuel filter off and it was full of rust and had at least a cup of water maybe more in the separator. Throughout this whole process I noticed the engine was blowing white smoke out the stack, its particularly bad when you rev the engine up but smokes constantly even at idle. When the engine is reved a few times and you let it return to idle, it idles slow then it will die the next time the pedal is pressed. Then it wont restart until it has sit for at least 5 min. The smoke smells like old raw diesel and burns your eyes and sinus not like antifreeze or condensation. The Oil Pressure Guage shows good pressure and it doesnt take long to build pressure once its started. I plan to do an overhead adjustment, change the fuel filter, replace rubber lines and put fresh fuel with some 2 stroke oil in it tomorrow. Is there anything else im overlooking that might cause this thing to knock and bellow white smoke like it is? Any help is greatly appreciated.
Thanks!
I purchased my first 5 ton about a month ago and finally got around to tinkering with it today . Its a 1983 m923 with a Cummins NHC 250. I bought the truck from a volunteer fire department in Oklahoma. The truck was advertised as "running and driving but has engine knocks and needs work." I decided that for the price it was worth the gamble and bought it. My initial impression after taking delivery of my new truck was that it was very straight and overall seemed like a solid truck. (Big thanks to 98G for the transportation! Great guy to deal with.) Needless to say I was extremely excited and happy with my new truck! I fired the truck up and immediately heard the pronounced knocking sound described by the seller. I gave the engine a little throttle to see if the knock got louder and it seemed to lessen as RPM's increased. I then attempted to move the truck into my yard and with the truck in gear the engine died as soon as I touched the throttle pedal. I attempted to restart it and it just cranked and cranked didn't even attempt to pop or start. I let the truck sit for about 5 minutes and then tried to start it again, to my surprise it fired right up. I rapidly moved it to the backyard and parked it. I pulled it out today to see what i could figure out and so far im not finding anything obvious. The Oil looks good no shiny specs or metallic pieces that I can see on the dipstick, in the rocker boxes, or from the small sample I removed from the oil pan. No oil in coolant or coolant in oil . Coolant level and oil levels are good. I used an infrared thermometer to measure the exhaust ports coming out of the heads and all were close to 190° at idle except cyl. #5 which was about 210°. I pulled the valve covers to see if i could see anything obvious but everything appears ok at first glance.
I then attempted to do a cylinder cutout test by holding open the injector rocker with a pry bar, but my results were inconsistent. Sometimes the engine would change rpm or sound slightly different but very indistinctly, nothing like pulling a sparkplug on a gas engine or doing a cylinder cutout test on a computer controlled diesel. Other times I got no reaction at all when the injectors were held closed and not one single injector responded consistently when doing this? I pulled the fuel filter off and it was full of rust and had at least a cup of water maybe more in the separator. Throughout this whole process I noticed the engine was blowing white smoke out the stack, its particularly bad when you rev the engine up but smokes constantly even at idle. When the engine is reved a few times and you let it return to idle, it idles slow then it will die the next time the pedal is pressed. Then it wont restart until it has sit for at least 5 min. The smoke smells like old raw diesel and burns your eyes and sinus not like antifreeze or condensation. The Oil Pressure Guage shows good pressure and it doesnt take long to build pressure once its started. I plan to do an overhead adjustment, change the fuel filter, replace rubber lines and put fresh fuel with some 2 stroke oil in it tomorrow. Is there anything else im overlooking that might cause this thing to knock and bellow white smoke like it is? Any help is greatly appreciated.
Thanks!
