LB 1914 3 cylinder diesel not running right

AlanWim · Dec 17, 2018

Background; The previous owner was not real good with repairing things. When I bought it the water pump was leaking out the weep hole. It would get hot after a while so I put a new water pump on it. It was still getting hot and that's when I realized how much stop leak the PO had poured into the radiator. I pulled the radiator off and boiled it out with muradic acid which helped a lot, but it still was getting too hot and now it was burning antifreeze. Pulled the head and put a new gasket on it. Not a lot of help. Took the head, had it magnafluxed and discovered a non-reparable crack. Could not find a Kioti head so discovered the Kubota D950 used the same head so I bought a "new" head from Kumar Bros. Spent over $500 on the new head. Set the valves and it runs a lot better, but still not right. Starts real easy when cold, but when warmed up sometimes it starts like an old Chevy 327 or 283 that has jumped time. Black smoke when starting then little to no smoke until it has run for a while then it seems to be burning a lot of oil from one cylinder then it will clear and run fine. Sometimes it has a slight lope when running. Idles down lower than it ever has since the new head installed. I'm fairly new to working on diesel engines but have a lot of knowledge of gasoline engines. Nothing is consistent on the way it runs. Don't remember the numbers, but compression was pretty even across all three cylinders. Sometimes it runs like a brand new machine. It seems like the longer I use it in a session the worse it runs. My question is where do I look next?

VictorW · Dec 17, 2018

If compression is even and where it should be, then I doubt it's engine oil. Usually black smoke is from to much fuel. Maybe one of the injectors is sticking, got a piece of dirt in it, or needs cleaned and recalibrated. I don't know the length of time between black smoke, little smoke, burning oil, runs clear, but sometimes an injector can throw out a good bit of fuel if not working correctly. This fuel gets blown into the exhaust and muffler. Once the exhaust and muffler get hot enough with the engine running, the excess fuel will start to burn off giving a dark exhaust color. Other than a bad injector, you have the injection pump but they normally don't act that way. I'm not sure why it runs worst as the sessions get longer but the black smoke sure points to a fuel related problem.

AlanWim · Dec 17, 2018

The black smoke doesn't last long after startup. When it seems to be burning oil it is a bluish white smoke. What gets me is that it doesn't last long and it sounds like a cylinder is not firing correctly. Would the injector pump be suspect? I just can't figure out why sometimes, but not every time, it starts like it's out of time when warmed up, like when a gas engine is out of time. By that I mean it acts like the battery just can't turn the engine over. New and tested battery also. If I let it rest a bit, it turns over and starts normally. Would a bad injector cause this? I honestly can't understand how it could, but I'm ready to try anything at this point.
Edit; forgot to mention, I also put a set of what was supposed to be rebuilt injectors on it. It will also put out black smoke if I put a hard load on it like pulling a hill in too high a gear. By that I mean if I'm going down the road in 8th gear and come to a hill without shifting down to 7th gear or lower. It also seems to bog down on moderately small hills. I've also changed the fuel filter.

jabelding · Dec 17, 2018

Have you checked compression on all 3 cylinders? Something else might be cracked or the PO hydrolocked the cylinder with the coolant leak and bent the rod in that cylinder causing low compression.

ritcheyvs · Dec 18, 2018

Have the fuel and air filters been recently replaced?
Black smoke is generally fuel that is not completely burned. Perhaps not enough air getting into the mix or poorly atomized fuel (some droplets too big to burn in available time).
Sooty exhaust under heavy load is common: more fuel injected than can fully burn. Some white smoke (unburned fuel) for a few seconds right after startup is not unusual. But intermittent soot under light load is not normal.
I wonder if there could be am air leak into the fuel line between the tank and the feed (kift) pump or partially blocked fuel outlet in the tank. It's not intuitive but lack of good fuel feed will cause black smoke. A failing lift pump can do this too
Injectors are the most likely cause. Even tiny amounts of dirt/grit can foul up injector operation. Any Diesel shop can pop-test the injectors to see if they open (pop) cleanly at the right pressure and produce a good spray pattern.
You might try running a can of Diesel Purge through the injection system to see if that helps. Cheaper than pop-testing.
I would start by checking the simple/cheap stuff (like air leak) first.

jabelding · Dec 18, 2018

Also if a cylinder does not fire but has fuel dumped into it, that fuel will go out into the exhaust manifold and will cause smoke.

ritcheyvs · Dec 19, 2018

jabelding said:
Also if a cylinder does not fire but has fuel dumped into it, that fuel will go out into the exhaust manifold and will cause smoke.

True, but unburned (as opposed to partially burned) fuel produces white smoke.

AlanWim · Dec 19, 2018

I had changed the injectors to supposedly rebuilt ones so I put the old ones back in yesterday and it runs somewhat different. Seems to be a little more white smoke at times and none at other times. Also ordered a new air filter. I'm planning to take the rebuilt injectors to have them tested. I am working on posting to you tube a video of it running. When I get it done, I'll post a link. Thanks for all the suggestions so far.