Car won't start

[Fii]

Today we checked the codes - nothing.
Then we unplugged all the injectors and measured voltage on the leads. Now it was fine - 12V on one lead and nothing on other. When cranking I could see needle moving a little bit on my analog voltmeter when connected to ground lead on the plug, so I believe, that ECU is working fine as well. So there is voltage on the injector leads and there is spark with the plug unplugged. Could it be that when the plug is back in there is no spark? But spark has to go somewhere and I saw no sparks in the engine bay in the dark, while cranking with plugs in their places.

We even tried to tow the car for several kilometers, and still nothing

The only things that come to my mind is changing the plugs and the plug wires, as well as playing with ignition timing.