First there was occasional white smoke, loud engine rattle, cutting out on full throttle and poor starting. the injectors were serviced but the engine has refused to start.

If your Kubota ZD28 is starting at wide open throttle with black smoke coming out of the exhaust and the throttle is not working, it could indicate a problem with the fuel system or throttle linkage.
Here are a few potential causes to consider:

1. Incorrect injector pump timing: If the injector pump was not installed correctly or the timing is off, it can cause the engine to start at full throttle with black smoke. You may need to re-time the pump to resolve this issue.
2. Clogged fuel injectors: If the fuel injectors are clogged, they may be supplying too much fuel to the engine, causing it to run at full throttle with black smoke. You can have the injectors cleaned or replaced to fix this problem.
3. Faulty throttle linkage: If the throttle linkage is not properly adjusted or is broken, it can prevent the throttle from working properly. Check the linkage to ensure it is properly connected and adjusted.
4. Air intake system: Check the air intake system for any blockages or leaks. If the engine is not getting enough air, it can cause it to run at full throttle with black smoke.

It's important to address this issue promptly, as running the engine at full throttle can cause damage to the engine and other components. If you're not comfortable diagnosing and fixing the issue yourself, it's best to take your Kubota ZD28 to a qualified technician who can diagnose and fix t

Diesel engine presumably?

White smoke is probably unburned/partially burned fuel - suspect poor injector spray patterns (low break-off pressure in pre-common rail) as a starting point.

Other possibilities are incorrect injection timing and low compression, assuming any preheat system is in good order.

Venkata, According to Injectorrx.com: "
Fuel injector symptoms for bad, faulty, dirty, clogged, or leaking injectors are :

• Starting issues



• Poor idle



• Failed emissions



• Poor Performance



• Engine does not reach full RPM



• Increased fuel consumption



• Rough engine performance



• Surging and bucking under various throttle loads



• Smoke from the tail pipe



• Engine Knock or Detonation which can lead to catastrophic engine failure



• Pollution"

Venakta: I have had very good luck with a fuel injector cleaner sold by Advanced Auto called KX44 but some people like Seafoam. It is a cheaper place to start than with a mechanic.

that is a service engine light and if you were blowing white smoke sounds like you have a head or head gasket problem as you over heated engine

no 4-3 or 3-2 downshift
uncontrolled downshifts outside range of kickdown switch
poor acceleration from stopped position
parking pawl will not engage
selector lever does not engage in r or p
engine will not start in p or n position
smoke in exhaust (fluid loss)
fluid loss between torque converter & primary pump
howling noise when changing gears (under full load)
howling noise which increases as engine rpm increases
1st gear & reverse too loud
3rd gear too loud
rattling noise at 1500 rpm in all positions except r
light grinding noise in p & n positions
rolling noises when driving in reverse
vacuum control circuit
Vacuum Control Valve (E300D & S350D)
Vacuum Amplifier (E300D & S350D)

any smoke could be a fuel knock if u have a injector leaking off.

The turbo will not cause black smoke. White smoke, yes, if its passing oil into the engine, but not black.
First check that the air intake and filter is not blocked, check that the air hoses from the turbo and intercooler are not collapsing when given throttle.if thats ok, then get the injectors tested, if they are ok then you need to get the injection pump serviced. Black smoke is a result of overfuelling, either by the poor dispersal of fuel from the injectors or the pump, or blockage of air into the engine on the intake system.
Hope that helps

Blown head gasket for sure if its a petrol engine.

If its diesel then its overfuelling.

i have a nissan b-14 idle roughly sometimes cut off when in traffic. any solutions???????

sounds like an ex reps car too me ...high mileage and well thrashed