Intermittent non start

Hello everyone

Got a very interesting case study here that i would like to update as it unfolds.

Vauxhall Corsa
2014
1.2 engine
A12XER

The fault is an intermittent crank but no start. I started to look at this on Friday 10/03/2017 but i didn't get to the bottom of it yet and would like your opinions.

Whether the car is hot or cold it makes no difference. It will start first turn of the key for about 15-20 times then on the next crank it just turns over but will not fire. If i keep cranking it will not start but if i stop cranking and crank once again it starts straight up no problem. I have scanned all modules with Tech2 and there is no fault codes stored in any module. My first thought was bad crank sensor but when it doesn't start live data shows an RPM and the tacho in the dash shows RPM. This engine has a Crank sensor and 2 Cam sensors on both inlet and exhaust camshafts. I have scoped all three sensors during a no start event.




As you can see the signals look good during the time it doesn't start. Next thought is the engine needs compression, fuel and spark. I can check spark and injector pulse on the scope so i did..

Below shows a no start event followed by a stop cranking then a perfect start up straight after.



Here is a zoomed in on the no start event. Green is obviously the injector, Yellow trace is secondary ignition with an ignition prob, Blue trace is coil control and red is coil current. The confusing thing is how can i have spark and fuel injection and no start? One thing i notice between the start and no start is the secondary ignition Kv. I did swop a good coil pack and still had the same issue. The engine sounds good during the no start event. It sounds like it has good compression. Both cams have variable timer solenoids.




Where would you guys go next?

I noticed you have a trigger set. From my experience, that could bite you if you are encountering intermittent signal dropping out. I'm sure you know this. But a trigger will hold the screen from the last triggered event even though currently the signal is not present.

I'm not saying that is even relevant to what is happening to you. But my eye noticed that.

I'm going to study your captures a little more, but I assume the waveforms you uploaded match exactly to when it does start. Right?

Thanks for the reply. Good reminder about the trigger. As far as I can see they match except the secondary Kv. It's higher when it starts but I put that down to cranking vs running.

I didn't have time to look through it carefully but have you checked fuel pressure during no start ? Maybe the relay isn't closing or isn't receiving the command it looked like you had everything else during no start

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Excellent thought and yes I did check it. 55psi during the no start event and also during cranking when it didn't start I sprayed brake cleaning into the intake and it didn't fire. It's weird. I need to go through everything again. I'm clearly missing something!! Haha

Does applying any amount of throttle during the no start event have any effect? Seeing as how everything else is checking out, this may be an air intake issue i.e. a dirty throttle body. I wonder if comparing cranking vacuum during a normal start and the times it doesn't start could pinpoint this?

Checking intake vacuum when it starts and doesn't is a good point. I will check that. I did give it a massive air leak and still got the no start problem.

Hmm but you have spark when it doesn't was that confirmed by scoping trigger voltage or by kv and a cop paddle? My thought here is maybe you have an issue on the key on power side of the coil not the trigger

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I scoped the trigger, current at the coil and secondary with a cop paddle . Also I haven't shown but I also removed the fuse that supplies coil and injectors and fitted a fuse buddy and measured current that way. All good when it doesn't start. I will revisit all these tests again incase I missed something.

Well maybe pull a coil and put a spark tester on during no start if you have introduce extra air and extra fuel and it didn't start then I would quadruple check spark your spark
I have a hard time seeing your captures on my phone but I notice you said the kv were lower during no start then when it starts what are your kvs at both times?

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Is there a way to see throttle angle when car doesn't start? If it is higher percentage than normal when car won't start, it might be stuck closed.

Is this car fly-by-wire or throttle body? If throttle body, I would run tests to ensure your Idle Bypass Valve isn't sticking. I perform these tests via bi-directional functional tests. I try to verify it smoothly opens and closes. I have had decent luck cleaning them if they get stuck. If fly-by-wire, perhaps ensure your throttle plate is not getting stuck.

Can you post that .VSM? the 2014 A12XER Corsa no start then start.vsm. This forum won't let you upload .VSM files directly but if you compress it in a .ZIP then you can upload it.

Would be nice to zoom in on the waveform and really check to see what's going on between the no start and start.

Hi guys,

I was wondering if anyone ever got to the bottom of this issue? I believe I have the same thing on my 2012 A12XER Corsa D - intermittent crank no start. Can't seem to get to the bottom of it. I have replaced:
1. Crank sensor
2. Throttle body
3. Fuel Pump
4. Coil pack, spark plugs
5. Engine and coolant temp sensors

The problem persists - every few starts (maybe 1 in 5) I get a crank no start. I can let it crank for 10+ seconds and nothing. Release the key and try again and it will start right up! No issues at all once it's started. Very frustrating. Don't think it is the immobilizer as I never get the flashing spanner. There are no codes stored.

Any idea what else could be causing the no start? I'd really appreciate any insights!

Kind regards,
Ben

Hi mark. I have the same issue as you had on the corsa a12xer, I have checked everything multiple time and can’t get my head round why it won’t start. Did you get to the bottom of this issue if so what was the issue and how did you test it to get the fault rectified.
Thanks Matt

I have the same issue as well, scoped all the sensors all looking really good. Did think I resolved it by cleaning throttle body but returned again. Totally stuck now as I don’t have the time to spend on the vehicle. Customer has reported that they think it’s lacking in power but I’ve not been able to confirm this.

I too have exactly the same issue with my 2011 Corsa D engine A12 XER. It has been like this for over 3 years, no worse no better. Fails to start on first try maybe every 1 in 5+ times and will always immediately start on the second turn of the key! Car otherwise runs perfectly.