No spark while cranking until key of switched off

[DROPthatCLUTCH]

Hey guys,

Been working on diagnosing a random no start problem that happened out of the blue. Parked the car on Sunday, went to cruise it the next weekend and no start.

It cranks and I'm getting fuel pressure, but no spark at all until I switch the ignition off then it throws a single spark.

I was sure it was an igniter problem but I changed that and still nothing...

Any help with the diagnosis is much appreciated.

Cheers

So I'm getting 1.2-1.3 ohms at the 1 & 3 and the 2 & 3 pins For the primary resistance test. So it's a bit over spec. I'm gonna get another coil pack and I'll report back.

 

[luv2rallye]

Check CAS, CPS, ECU, and wiring/connectors.

 

[darknezz7]

Check the ecu coolant temp sensor, its the 2 wired one, check the wires and for voltage. On our car this unplugged makes the ecu not fire the injectors or spark, I've heard not all cars are like this though.

The only other thing that will cause no spark is the crank sensor. I dont know 1g's but yours is a cam and crank in one, the cas, I believe.

Yeah check all the wiring for the coil pack, resistor, are you getting voltage with key on?

If no get a pinout diagram and check at the ecu, if you have at ecu theres a broken wire or short along the way to the sensor. If no voltage at ecu it might be flakey ecu

Which car is this on?
Any hacks done to the ecu harness?

 

[luv2rallye]

Check the ecu coolant temp sensor, its the 2 wired one, check the wires and for voltage. On our car this unplugged makes the ecu not fire the injectors or spark, I've heard not all cars are like this though.

That's not true. Unplugged it can make it run poor (incorrect mixture) but it will still run.

 

[darknezz7]

That's not true. Unplugged it can make it run poor (incorrect mixture) but it will still run.

Sorry to tell you, but on our car THE ECU WILL NOT send out spark or injector pulse with the 2 WIRE coolant temp sensor unplugged. 100% sure on this

Look it up, some do some dont.

 

[19Eclipse90]

Sorry to tell you, but on our car THE ECU WILL NOT send out spark or injector pulse with the 2 WIRE coolant temp sensor unplugged. 100% sure on this

Look it up, some do some dont.

The FSM says that starting the car is not "impossible" with a bad CTS, only "defective". A faulty sensor is capable of preventing the car from starting in cold weather, causing an unsteady idle, or improper acceleration. When the sensor becomes faulty, the ECU defaults to a coolant temperature of 80 degrees Celsius which keeps the vehicle "...in the safe driving conditions according to the preset control logic."

For argument's sake and to clear the air, I unplugged the CTS on my car (1G) this morning while running and it continued to run. The only thing it did was turn on the CEL. Therefore, it cannot cut spark or injector pulse.

 

[luv2rallye]

Sorry to tell you, but on our car THE ECU WILL NOT send out spark or injector pulse with the 2 WIRE coolant temp sensor unplugged. 100% sure on this

Look it up, some do some dont.

Do you really believe that ANY car designer would strand someone in the middle of nowhere (or a freeway) because the CTS sensor stopped working (or is unplugged) when the engine can easily run on default values? NO! I unplugged mine and it starts and runs fine (with CEL and running rich when warm). If yours does what you say then you don't have a stock setup or you have a wiring issue. [and BTW it looks like 19Eclipse90 took your challenge and did look it up proving you're incorrect].

 

[YZFR1]

I suspect a bad battery even if it's showing good voltage could cause that.

 

[darknezz7]

I didn't say it was what the fsm states, but it is what our car does, so maybe something is wrong, yes it was cold when
I tested this. I just know it was no spark but had fuel to the rail until I realized the cts was not plugged in all the way. I'll try it tomorrow.

If this one does it, some other may too, just sharing what I have experienced.

BTW on BMW's a bad cts can definitely make the car not start and run like complete crap, stall, no power, ect. Plenty experience with that too...