Hi all
In june our Roomster 1,6 stopped working while pulling a caravan on hot day, and I havent been able to fix it yet.
First symptom was that it started running on 3 cylinders (which it has been doing two times before, both time fixed by changing a ignition coil, both time in hot weather and stressing the engine a bit)
So I pulled over and started changing ignition coil by way of trying which one it could be, I always have one new coil in the car.
first I put the coil in the fourth cylinder, still running on 3cyliders, then I tried third cylinder, nothing, stone dead... Long story short the got towed and I picked up our other car.
Since then I have had diagnostics done with a quite ok hobby device (Vgate Maxiscan) with these codes:
P0688 "wiring short to positive, EC relay, ECM
P0301 "Engine mechanical fault, wiring, ignition/feul system, injector, ECT/MAF sensor, ECM"
Apart from checking for broken cables I have replaced two more coils, cam shaft position sensor, crank shaft position sensor, EC relay (not with oem, just similar relay), checked all the fuses and lastly I bought a used ECM.
I have tried with motor starter gas, no reaction, when trying to start a few times it smells gasoline in the exhaust, so I rule out fuel pump etc, I can also hear it as normal when turning the ignition on.
The used ECM was returned to the wrecking yard.

What is the next step?  Buying another ECM with ignition lock and keys to get a new immobilizer identity? (the ECM I tried did not have key etc)
what have I overlooked?  is there something simple in the codes I have overlooked, "P0688 wiring short to positive, EC relay" could it be a wire going to the relay that is broken?

The car get one or two more tries before I give up, help is much appreciated.

If you're not getting anywhere doing it the technical way, I'd be going basic with the fault finding.

 

Take the outlet pipe off the fuel filter, prime it and see if there's a decent amount of fuel coming out.

 

Pull the plugs out, see what colour and condition they're in. See if they will spark against the head.

 

Do a compression test.

 

Put a test "Noid" light on the injector plugs.

 

Pull the injectors out put them in some test jars and see if they're spraying, and spraying well.