Is the diesel electric throttle or mechanical? If its mechanical, this'll be easy to run, wiring's simple on mechanical fuel injected diesels.
Electric throttle? That's a different beast, but will be more friendly to using like an Arduino to control startup and throttle up procedures.

The throttle is mechanical so it is easily controlled with a servo and Arduino. I don't know about other electronics: do the pump need them? There was few wires coming from pump when I disassembled the car. Maybe throttle position?

Doesn't fuel pump need some engine data to be able to control injection timing. At least temperature and engine speed?

No, all you need is +12v to the Fuel Cutoff Solenoid on the back of the Injection Pump and the starter +12v and starter solenoid.

That's it. Everything else is sensors. If its a mechanical fuel pump as well, it probably doesn't even need a lift pump, the Injection Pump can handle pulling the fuel as well.

Engine speed on Diesels varies by manufacturer: On VW, the old 1.6 Diesels used the Alternator to actually provide engine speed to the Tachometer.  (W Pin on Bosch Alternators)

You first need to determine how many poles are in the generator.  That will determine at what speed you must turn it in order to get 60 hz.

Also 20kw is a lot of power.  Way more than a normal house would need.  This is going to take a lot of fuel to generate that kind of power.  In a good genset, you're looking at 1.5 gallons an hour.

One other thing, 20kw at 230 volts is 86 amps of power.  I don't think the windings in that motor will be up to that.

Here is a website that will have anything power generating related.  http://www.utterpower.com/chinese-horizontal-diesels-195-1100-1115-1125-and-others/

And good luck with your endeavour.

Thank you for the link.

The motor in question has four poles. So because of slip I think the running
speed would be somewhere between 1500-1600 rpm (50 Hz). The electric motor is
rated 22kW so yeah 20kW may be a bit too much load. But I don't think I'll need that much power.

I agree this is a bit overkill for normal house use but as motor was already available for cheap; why not to build a big one.

A friend of mine has built ~5kW generator using petrol engine but he has a bit problems with voltage and frequency stability as load varies. I think this bigger generator will produce more stable power as smaller ones.

I don't think the fuel consumption to be a huge problem because it's just a backup for longer power outages (1 to 2 days / year).