Have seen this happen before but was under unusual circumstances. Was at a location where another tech was performing maintanence on a lift and it done as you described. Checked unit and found wire broken on lpg pressure sensor and smoke was due to not removing dipstick when filling crankcase with oil. Comfirmed this by removing PCV hose from valve cover and finding oil in it. After talking with service guy found he had not let oil have time to drain in oil pan before starting engine. Wire was broken due to wire connection checks. Repaired wire, cleaned out remaining oil in hose and cleared code. Smoked for several minutes and cleared up.

Check your coolant level in the resevoir bottle and level in radiator, bottle should be filled to marked lines on the bottle , the coolant level sensor is inside the bottle, sometimes it sticks. You can blow very low amounts of air pressure in quick shots into the top 10-20 PSI(cover with a rag). Sometimes they stick and this helps, if not take it out and wash it out with hot water,check wires and connections and try again.

roadthec. i just replace the lp reglator is not smoking but the houers whent off after i connect the coolant level sensor. i foud it unploged. now my question is what i need to.

i just did it is running better. and whit out smoke. but i found the coolant level sensor disconect, i just connecte it back and the houers in the instrument cluster whent off. i unpluge the sensor and they come back on. any body knows why is doing this or what i need to do.

what is the engine oil level? if it is way overfull, you have a seal blown in the hydraulic pump.

mrfixit;
Your thinking is about what I would believe is correct. This is an issue which is more likely to be cause by a sensor or sensors which are not functioning correctly. An automotive style On-Board-Diagnostic II (OBD II) handset should be able to determine this.

I never saw a forklift smoke from burning LPG fuel. Oil or antifreeze burning causes smoke.

Wence;
Before we change a part which abt 800 USD and still may have warrenty if it operational life is less then 5 yrs. or less then 3000 hrs. let us install a Generic Service Tool (GST) on the OBD II link which is taped to the wire harness under the cup holder of the dash and find out which P code is being displayed so we can determine more accurately what is taking place and is the cause of the issue.

Replace the LP fuel regulator, it's dumping too much fuel into the system.