bob cat 870 smoke

bigdaddyterry · Sep 30, 2018

Got a used 870 that ran and works great. New to these things and when using last week it perodically started loading up and black smoking BAD for a minute or so then clean up and run fine. That was every 30 to 1hr. than it got worse and now every few minutes. Also revs up when doing this and will not shut off with the key. looks like fuel in oil also as its getting thin. please help, other wise it runs great. where do i look first. one thing i did see was the lever on side of pump that looks like its suppose to be hooked to throttle linkage on the motor is unhooked and gone but dont think it was ever there. Terry

bobbie-g · Oct 1, 2018

I'm not sure I know what a Bobcat 870 is. Model number? Maybe 873?

bigdaddyterry · Oct 2, 2018

bobbie-g said:
I'm not sure I know what a Bobcat 870 is. Model number? Maybe 873?

Sorry, yes 873 you are correct. i forgot it was marked wrong on the lift arm for some odd reason and previous owner told me that.

bobbie-g · Oct 2, 2018

bigdaddyterry said:
Sorry, yes 873 you are correct. i forgot it was marked wrong on the lift arm for some odd reason and previous owner told me that.

On the Deutz engine in the 873, there is a lift pump on the back of the engine, very easy to see and get to. Just above the dipstick as I recall. I've heard that occasionally the diaphragm in the pump can partially fail and let diesel into the oil pan. Bad from two standpoints. First, that thins the oil thus more wear on the engine. Second, and much worse, the oil/diesel mixture can find it's way into the cylinders (unsure how, I'm just going from what the Big Boys say) and you can get a runaway engine that can destroy itself, since you can't turn it off. Changing the fuel lift pump is really simple and fast. I think mine cost about $50. Holler if you need more info.

---Bobbie-G

foton · Oct 2, 2018

bobbie-g said:
On the Deutz engine in the 873, there is a lift pump on the back of the engine, very easy to see and get to. Just above the dipstick as I recall. I've heard that occasionally the diaphragm in the pump can partially fail and let diesel into the oil pan. Bad from two standpoints. First, that thins the oil thus more wear on the engine. Second, and much worse, the oil/diesel mixture can find it's way into the cylinders (unsure how, I'm just going from what the Big Boys say) and you can get a runaway engine that can destroy itself, since you can't turn it off. Changing the fuel lift pump is really simple and fast. I think mine cost about $50. Holler if you need more info. ---Bobbie-G

check the oil level if it is overfull, smell the oil if it smells like diesel do not run it till the fuel pump is fixed.