I have a Japanese imported subject vehicle of 1999 manufacture.
Unfortunately I do not have an owners handbook.
On the dash-board, mine is right-hand drive, at steering wheel level
is a push-push button with an emblem of a engine-block with an
electrical signal superimposed, with a small light which lights-up in
the 'on' position.
I am assuming that this button warms-up the engine-block to allow the
fuel to flow in low-temperature conditions?
I live in Southern Russia and believe you me, we do get some low
temperatures here:-)))))
What I would like to know is how I use this button.
When I switch-on the ignition, as well as waiting for the glow-plug
light to go out, do I switch on this control and wait for the light
to go out?
If I do not have to wait for the light to go out, how long should I
allow before attempting to start the engine?
I have not lived in Russia for very long and have yet to find a
garage, hence my MU sits outside at night and I have been having
trouble starting it first thing in the morning after a cold night.
Anyone advise a fuel-tank additive to allow the diesel to flow more
freely in cold conditions?
Many thanks.

I have the same model. There seems to be a lot of confusion as to this switch, even with the handbook.

What it does is allow the engine to warm up faster. The wiring diagram seems to show it connected to a heater which is in the cooling system.

I have tested mine by placing a thermometer on the dash above an air vent when the engine is cold. I started the engine without this switch being pressed and timed the rise in temperature to a specific level. The following day (same outside temperature) I repeated this experiment with the switch depressed. The engine heated up to the same level in a much faster time. I cannot remember the precise details now as the experiment was three years ago but the difference was of the order of five times faster.

The heater has a cut-out when the engine reaches a certain temperature (the light on the switch will go out at this point) so I just leave the switched depressed. If the engine is cold enough to need it, it switches itself on. In winter I leave the switch on, in summer I leave it off.

Howard Neil

I also need information about the 4JX1 engine , because i have one in my shop that won't start .
It is a 3.0l diesel engine.

I have a 2000 model 4jx1
Turn the switch on and leave it on.
It is a quick warm up button but it is also automatic.
It is designed to come on at temperatures below 15deg.
It will automatically switch off when engine warms sufficiently. If the outside ambient temp is above 15 then it wont engage the system at all.
Start the engine after the glow plug light goes out as you would for most diesels.
5w 30 oil or lower is needed in cold climates like you describe.
When you say wont start does this mean wont turn over at all or turns over but wont fire?

The quick heat system apparently is not an electric element at all. The system in fact when enabled places a restriction on the exhaust and thus creates back pressure and accelerated. This is very simular looking to an exhaust break causing simulat misconecptions about an exhaust brake being fitted.
This is a vacume operated diaphram controlling a gate valve below the turbo.

While I believe this to be the case with the earlier (3.1 litre) engine, this is apparently not so with the 4JX1 engine. The official Isuzu workshop manual wiring diagram for my 4JX1 clearly shows wires attached to this switch and leading to an electric element.