My car wont start, after being put in the garage engine running perfectly 3 months ago. There is no spark at the plugs, Car fitted with a Sigma Thatcham cat 1 alarm/immobiliser 2 years ago, normally very reliable. Engine spins fine but no sign of starting. Plan to look into alarm immobiliser first by checking if 12V supply to coils is ok, then to look into sensors/Electrical control unit. Does any one have any other suggestions or able to confirm my logic in checking the system out. Thanks, Gareth
I had the same issue last summer... it turned out to be a connector in the passangers foot well. if you are sure you are getting no actual spark, then you have to look at coils, wires etc... no much in the way of circuits... the fly wheel sensor is a potential... or you may have a connection coming loose in the trunk area... that does not allow spark... if you do have a spark, then you have to look on the wiring diagram and track where the connectors are... I would start there. the wires become brittle over time, and heat etc... best of luck
Thanks to all of you who have replied so far I will try looking at connectors (corroded or just come loose) and flywhell sensor. Ta for taking the time. gareth
I guess one question is what does the immobilizer "immobilize" when it is set off? That would be helpful to know when considering if it might be a cause.
The immobiliser does cut the ignition circuit that leads to the coils so I may try and put this back to factory with the aid of the alarm techie to eliminate. But something I can do first is assure all connectors are making good contact and if they are and no power to coils it could be the immobiliser although I am not sure how the flywheel sensor fits in to the equation. Does this have to be operational and is the circuit in line with the supply to the coils. In other words if the flywheel sensor is duff will it prevent power getting to the coils?? Any advice much appreciated
checked out the fuses/relays, no obvious problem . A connector block fixed to the back of the passenger footwell plate had come adrift from its fixing but I am pretty sure this is not an earth connection just a way of fixing the unit to the plate to keep it tidy. Checked out the marelli unit in the rear trunk area and remade the earth connection to the frame, a little corroded to begin with but this did not cure the problem. I am still looking for the solution, still wont start. Plenty of fuel vapour around when turning over engine so must be no ignition problem. Alarm immobiliser and flywheel sensor next port of call.
A bad flywheel sensor would keep the coils from firing (indirectly). The computer needs a good timing signal from the sensors to give the firing voltage to the coils at the right time. If it can't make the calculation because of no sensor signal (or too weak a signal) it will not fire the coils.
Well guys, I can report the fault was a broken flywheel (TDC) sensor. I detected the fault by reference to the fault finding chart in the back of the technical manual. My hands and arms were too big to get to it, its really awkwardly tucked away round the back of the engine, so had a specilaist fit it and service the car at the same time and stamp the service book. Price was not too bad, only waste was the cost to tow the car there. Looking for a trailer or bogie with winch now so I can get the car around if another difficult repair arises. So look for loose or corroded connectors, bad earthing to the coils/ECU, and flywheel sensor. Thanks for all those who sent advice and full marks to those who new the answer to my dillema.
