is this no start something new? iow, your car started fine and ran fine beforehand?
Any work recently done, that might have caused this?
to the problem:
so you changed the relay...which one? the red stripe one?...with the correct type relay (Bosch 0 332 014 112)
on the sipea relay, the AUX motronic relay, did you check the 15A fuse?
what I would do:
as Christopher says, first thing to do is check spark.
no spark, then
check voltage at coil, key on, for battery voltage from one of the small terminals to ground?
now put a small 12v test light between the neg and the pos coil connections...crank the engine...does the light flash?
(my guess here, would be no flashing therefore no tachymetric signal.....correct?)
no spark is 90% of the time a bad motronic red stripe relay and 10% other things
other things being: crank sensor (test the ohms, about 520 ohms is correct....the crank sensor 3-pin plug is up front, underhood, driver's side near windscreen filler cap, test between the centre pin and one of the outer pins, one pin reads out, the other does not, so test centre to both-one after the other-to be sure you have the right one!
You are testing resistance at the plug FROM the sensor, NOT the plug going back to the ECU!...doing that might fry your ECU...
battery being OK or even new is one thing, but if you do not have 11.5V 'whilst cranking' your computor won't work, it's that simple, so do check that or we will be running around in circles