Engine not starting

Make/Model: Suzuki Jimny (soft top)Year: 2004, built in Spain (Santana)
Engine: G13BB (1.3, 16v, petrol, sequential multipoint injection, with CKP and CMP sensors)

ECU:
Brand: DensoSuzuki code: 33921-81A4Denso code: 112200-0841
   Visually inspected: no burnt components, smoke traces, corrosion or oxidation, neither on the PCB nor in the connectors.

. Repairs:
- Replaced cracked cylinder head with a reconditioned one.
The replacement head came with a different camshaft trigger wheel, so the original camshaft was reused.
Original:
 
New one:
  -
Before disassembly, the battery was disconnected. After reconnecting all connectors, the battery was connected again. The chance of a short circuit is practically zero.
- The crankshaft oil seal was also replaced (front one) 

Symptoms:- The engine cranks, sometimes tries to start, but never fully starts.Video: [ drive.google.com/file/d/1ojr19VQdSS\_RdG...fr/view?usp=drivesdk ]( drive.google.com/file/d/1ojr19VQdSS_RdG4...fr/view?usp=drivesdk )
- Injectors 1 and 4 work normally.
- Injectors 2 and 3 give a single initial pulse, then stop.
- Spark only appears on cylinders 2 and 3. No spark on 1 and 4 (maybe one initial spark).
- Injection and ignition faults mirror each other.
- RPM signal in OBD appears sporadically.
When it does, the engine almost starts.
.- Disconnecting the CMP sensor (3-wire) does not change the behavior.
Tests and diagnostics performed:CKP sensor (2 wires – green and brown, which become blue and pink at the ECU): 
- Replaced with three different sensors – all measure 450 Ohms and produce \~300 mV AC signal (measured at ECU) during cranking.
-  Wiring from sensor to ECU replaced with new shielded wires.
- ECU pinout confirmed, sensor correctly connected.-
ECU detects disconnection of CKP sensor and activates fuel pump.
ECU logs error code when CKP is disconnected. 
CMP sensor (3 wires – green/black = +12V, white = signal, black = ground
:-  Gets correct voltage.
- Signal is generated and detected by the ECU (fuel pump activates upon reconnect).
- Tested both off-engine and installed – works in both cases.
- ECU does not log an error code when CMP is disconnected. 

Injectors and coils:
- All injectors tested individually – fully functional.
- Injection is sequential. Cylinders 1 and 4 inject fuel. Cylinders 2 and 3 do not (or give one initial pulse).
- Injector wires checked to the ECU – continuity OK.
- Coil packs for cylinders 2 and 3 produce spark. 1 and 4 do not (or spark once).
-Tested with other coils – same results
.- Spark plugs are new.-
Driver transistors in ECU are likely not dead – all outputs give a pulse at the beginning. 

Timing:- Checked and aligned to timing marks.   

Any help is greatly appreciated 
Thank you 

How do you know injectors 2 & 3 are not working? Is there no fuel to these cylinders?

Or do you have a misfire on these two cylinders?

I assume that cylinders 1 & 4 both fire, but that isn’t enough to get the engine running?

Assuming you have checked ignition and fuel pressure can you check the injector wiring to see if you have an injector pulse? If not it might be wiring, either trapped or a connector.

Engine is trying to start briefly. It I put brake cleaner on intake, is running few seconds.
I removed the injector rail and had someone crank the engine — I noticed that injectors 2 and 3 weren't spraying fuel.I swapped the connector from injector 1 to injectors 2 and 3, and they both sprayed correctly.I measured with a multimeter — all four connectors have +12V.Then I used a test LED on each connector: injectors 1 and 4 show normal pulsing, but 2 and 3 flash once or twice, then nothing

If you have fuel & spark (at the correct time) on cylinders 1 & 4 the engine should start & run, albeit not very well, but, it should run.

Have you checked for spark on all four cylinders? In a no fuel situation (no fuel at all), the engine should start & run on starting fluid for as long as you keep spraying the starting fluid.

If you can't do either of the two above you need to figure out why and cam timing would be the first place I would look, because that would have been disturbed when the head was removed.

You say the head was replaced - new head? "good" used head? or completely unknown head?

Is a refurbished cylinder head, complete, pressure tested. The camshaft is mine from old cylinder head. 
Both crankshaft and cameashaft are aligned at marks.
Even if timing is bad and ignition is not working, injectors 2 and 3 should work, even if engine won't start.

I would suspect a wiring fault or bad connection to the injectors. If you swap the injectors (or wiring) over does the problem move or stay with cylinders 2 & 3?

The other thing i can think of is the crank position sensor, is it ok?