hj6o

I'd be looking a the valve stems and seals for wear if the head's never been off. If it's black smokecheck the injectors.

Is it starting ok maybe the glow plugs aren't heating a cylinder or more up enough before starting. Have you thought of taking it to a good reputable diesel mechanic If he kept it over night or you dropped it off in the morning he could start it later that day and seen what happens it may be something minor.

Most likely just one or two glow plugs are gone. Simple to check on the 2H. Just take off the bar that joins the 6 glowplugs and use a multimeter to check for continuity to earth for each plug. If no continuity, the glow plug is dead.
Up to you whether you just replace the dead ones. There were several different glow plugs - I think the superglow plugs came in in late 1983 - make sure you get the right ones for your HJ60.
And of course I might be barking up the wrong tree, but glow plugs are simple to check and cheap to replace. If you have to replace a glow plug be careful when you remove it - they can get stuck and break off.

What colour is the smoke, white, black or blue?

Definitely check the glow plugs .... a the first winter after I baught my current diesel hilux .... it got hard to start ...... checked the glow plugs ...... 4 out of 4 NBG.

Started fine in all but coldest mornings.

Another known issue with toyotas, is smoke when running oil that is too thick.

The head does not drain quickly enough, the oil level rises and oil gets past the valve seals.

15w40 .... thicker oil has no advantage.

cheers