Grey smoke

[Gdubs]

I just rebuilt my d902 motor, and it’s running good, rpms are correct, plenty of power, but has a very faint, and constant greyish smoke from exhaust.

the only calibration on the motor there wasn’t a setting for in the shop manual was the governor bolt in the front of the motor and the bolt that’s behind the injector pump, that pushes the rack forward.
All the other settings (valves/timing, etc) are to spec.

It does bog down when going up a steep incline as well
Which it never did before

any info to point me in the right direction is appreciated.

 

[Fordtech86]

Grey smoke from a diesel is typically caused by lack of heat in the cylinder.
What all was done during the rebuild and how much run time does it have since?

My first thought was it just needs to be ran more to fully seat the rings. Also water in fuel could cause it if it has sat for any length of time during the repair.

 

[Gdubs]

Pretty much a total red do on motor

Block machined, new liners pressed in
New pistons/rings
New cylinder head
All new gaskets top and bottom
New injectors
IP rebuild
All new fuel lines
all new filter/fluids

Has maybe 15-20 hours on it now
New fuel

I did not replace glow plugs, but bench tested them all and they glowed red

do glow plugs heat cylinder during operation or just help ignite fuel during startup?

 

[Fordtech86]

do glow plugs heat cylinder during operation or just help ignite fuel during startup?

They just aid in heating the cylinder before starting and during cranking on some models. Im not familiar enough with Kubota to know what models do what, but they for sure won’t be on after its been started (possible they may stay on for a few seconds after starting, but Im not sure if Kubota does that). All the heat required for ignition is created by compression.

 

[Fordtech86]

Has it done this ever since the rebuild, or did it just start recently in the 15-20 hrs you have ran it?

 

[Gdubs]

Ever since rebuild, I’ve been waiting for it to break in like you said, but now getting nervous I screwed something up.

 

[Fordtech86]

One more thought, and you may want to wait for the pros before considering, but would the injection pump need retimed after the rebuild of the pump. I have zero experience with mechanical diesels, so I’m not 100% on that.

 

[Gdubs]

With the kubota d902, the only thing that affects IP timing is the number shims under it, and I put as many back as came out, but it’s possible that I need to either advance or retard the timing I guess. It’s not a huge endeavor to remove pump and ad or remove a shim

 

[xrocketengineer]

Grey smoke from a diesel is typically caused by lack of heat in the cylinder.

Can the coolant thermostat low temperature come into play in this like with cars?

 

[Pau7220]

The shims are to adjust manufacturing tolerance differences on the IP mounting deck height. That's why the shims stay with the block. If that deck height wasn't changed the timing shouldn't change. Was the IP rebuilt by an injection shop? We're the injectors OE? Wait for the techs before changing anything.

 

[Fordtech86]

Can the coolant thermostat low temperature come into play in this like with cars?

Not in this case from what I see.

 

[Blue280z]

I played with governor limit (5 IN DRAWING BELOW) on my D600. I could set the heavy-load fuel adjustment so that it:

1. billowed black smoke (LOTS OF SOOT, with lots of power)
2. had no smoke (and low power)
3. had grey smoke and reasonable power (where it is now...SOME SOOT ...SO GREY.... I plan to back it off a little more)

Have you adjusted the valves?





Here is location of screw on a typical Kubota engine
7

 

[Blue280z]

btw the other governor adjustment (on flywheel side) is for fuel at idle:

 

[Blue280z]

 

[Gdubs]

I played with governor limit (5 IN DRAWING BELOW) on my D600. I could set the heavy-load fuel adjustment so that it:

1. billowed black smoke (LOTS OF SOOT, with lots of power)
2. had no smoke (and low power)
3. had grey smoke and reasonable power (where it is now...SOME SOOT ...SO GREY.... I plan to back it off a little more)

Have you adjusted the valves?


View attachment 66413


Here is location of screw on a typical Kubota engine
7 View attachment 66414

Yes that’s the bolt I bc wasn’t sure how to set other than trial and error.

and also yes, I adjusted valves last week (eoic method)

 

[Gdubs]

Ok so I should just start backing that bolt off and run it, and tweak it from there and that’ll affect power? And if I back off/tighten the bolt that holds the IP rack in position that will only affect my engine at idle?

 

[Blue280z]

There are two screws.
- One adjusts idle only (on fly wheel side of injector pump)
- The other adjusts under-load fuel (on fan side of injector pump)

Here is what to do:

1. Remove anti-tamper cap/dust cover from adjustment screw on fan side of injector block.
2. Warm-up machine
3. Note the angle of the slot in the screw (this is your nominal fuel amount at load)
4. Loosen the one or two nuts on that same screw. (two 10mm wrenches is all you need....they lock it in place). Be careful not to spin the screw
5. Back out the screw one full turn (to add more fuel) then snug the locking nuts. (I turned it out by hand but a small stubby flat screw driver with a thin tip... or a snapped off box-cutter blade segment works).
6. Test drive and note power and black smoke under load.
7. If you still need power repeat step 5 and 6. (Turn the screw back in to reduce smoke under load)

I found that 1/2 a turn on my little 0.6litre 3 cyl made a difference so you may find that more turns are needed on your bigger 0.9 litre engine. Make as many fine adjustments in either direction as you need.

I experimented by turning in too. Continued turning in will eventually remove all smoke then it will also take away power under load.

 

[Gdubs]

There are two screws.
- One adjusts idle only (on fly wheel side of injector pump)
- The other adjusts under-load fuel (on fan side of injector pump)

Here is what to do:

0. Warm-up machine
1. Remove anti-tamper cap/dust cover from adjustment screw on fan side of injector block.
2. Note the angle of the slot in the screw (this is your nominal fuel amount at load)
3. Loosen the one or two nuts on that same screw. (two 10mm wrenches is all you need....they lock it in place). Be careful not to spin the screw
4. Back out the screw one full turn (to add more fuel) then snug the locking nuts. (I turned it out by hand but a small stubby flat screw driver with a thin tip... or a snapped off box-cutter blade segment works).
5. Test drive and note power and black smoke under load.
6. If you still need power repeat step 4 and 5. (Turn the screw back in to reduce smoke under load)

I found that 1/2 a turn on my little 0.6litre 3 cyl made a difference so you may find that more turns are needed on your bigger 0.9 litre engine. Make as many fine adjustments as you need.

I experimented by turning in too. Continued turning in will eventually remove all smoke then it will also take away power under load.

 

[Blue280z]

FYI the IP Rack slides left and right (as viewed facing the installed pump).

When the IP rack slides fully to the left, it is the lowest fuel position and that is where it sits at idle. The idle adjusting screw on that side adjusts idle fueling.


When the IP rack slides fully to the right, it is the at the highest fuel position and that is where it sits under load. The load adusting screw on that side adjusts under load fueling (and it also impacts non-loaded fueling slightly).

 

[Gdubs]

yeah I made things worse by stripping the threads of the bolt hole in the gear case Cover

I’m think I’m screwed now