Intermittent starting issue. Advice sought

[StescoG66]

Wonder if anyone has experience if this and can advise.

Son has a 2017 Corsa 1.4 {Corsa E in VX/Opel parlance}, 75k miles which has intermittent starting issues. No rhyme nor reason, but it occasionally takes an ordinate amount of key churning to start. I iinitially suspected a weak battery and while it is still the original it was reading 12.6v the other day, however it was down at 12.1v in the recent frost so needs monitoring. Anyway......
Before I start firing a parts cannon, does anybody have any ideas or experienced this issue? My thoughts are an intermittent sensor issue - thinking crank sensor is my main culprit now. No error codes present or imminent either.
Thanks in advance.

[GreenV8S]

Is it cranking at the normal speed when it declines to start?

A battery that is down to 12.1 Volts at rest is either flat or damaged.

Does the problem show up during both hot and cold starts?

[StescoG66]

GreenV8S said:

Is it cranking at the normal speed when it declines to start?

A battery that is down to 12.1 Volts at rest is either flat or damaged.

Does the problem show up during both hot and cold starts?

Thank you

Yes cranks at normal speed when it doesn’t start, and matters not whether hot or cold

[E-bmw]

GreenV8S said:

A battery that is down to 12.1 Volts at rest is either flat or damaged.

^^^^ Wot 'e said.

12.6v is good & shows full charge but every 0.1v under that loses around 15% of charge.

If it isn't starting try to think on & measure what the voltage is dropping to when it is turning over.

Have you tried waiting after turning the key before going the final step to hear (with the door open) if the fuel pump can be heard priming the fuel lines?

Is it better/worse if it hasn't been driven for a few days?

[stevieturbo]

StescoG66 said:

Wonder if anyone has experience if this and can advise.

Son has a 2017 Corsa 1.4 {Corsa E in VX/Opel parlance}, 75k miles which has intermittent starting issues. No rhyme nor reason, but it occasionally takes an ordinate amount of key churning to start. I iinitially suspected a weak battery and while it is still the original it was reading 12.6v the other day, however it was down at 12.1v in the recent frost so needs monitoring. Anyway......
Before I start firing a parts cannon, does anybody have any ideas or experienced this issue? My thoughts are an intermittent sensor issue - thinking crank sensor is my main culprit now. No error codes present or imminent either.
Thanks in advance.

Why would you fire the parts cannon, when it sounds like you have done zero testing either ?

And what does "key churning" mean ?

If you suspect a weak battery, this should be easy....is it or is it not cranking over properly ? What is battery voltage during cranking ? Have you actually tested anything ?
Static voltage with no load is largely meaningless.

Ideas...yes, test. And if you suspect crank sensor ( for whatever reason ), again....test. Are you getting a sensible rpm reading during cranking ? Can you scope the output to see if it is sensible/valid ?

[StescoG66]

Right, apologies I will try to be clearer.

Key churning - turning the starter continuously. 20 seconds turning the starter, sometimes 2 or 3 attempts until it fires. The starter turns fine, it’s not sluggish and doesn’t ‘bog down’ while turning over.
It’s totally random, does it whether warm or cold outside, does it with engine either hot or cold. As I say, it’s intermittent and totally random, hence why I think a sensor somewhere is giving spurious readings.

[stevieturbo]

StescoG66 said:

As I say, it’s intermittent and totally random, hence why I think a sensor somewhere is giving spurious readings.

Then test, don't guess.

And if it is not starting for extended periods, that is not intermittent. That is a fault very present. That is the ideal time to be testing to establish what is wrong

[StescoG66]

Hi get it, yes test. But test what?

[E-bmw]

StescoG66 said:

Hi get it, yes test. But test what?

Test everything you suspect obviously.

You are asking for advice & getting it, now is the time to use/follow it.

Have you tried what has already been suggested a couple of times yet?

Never ever randomly change stuff in the hope of accidentally finding the fault, it is feckin' expensive & wasteful.

Battery voltage when cranking.

Fuel pump priming.

Get/borrow a code reader as they are very good for checking "live data" on engine sensors etc.

For starters

[stevieturbo]

StescoG66 said:

Hi get it, yes test. But test what?

Well at the risk of repeating myself, at this most very basic level.

hard to help people, when they ignore the help.

stevieturbo said:

Ideas...yes, test. And if you suspect crank sensor ( for whatever reason ), again....test. Are you getting a sensible rpm reading during cranking ? Can you scope the output to see if it is sensible/valid ?

[StescoG66]

Ok, hung up the over thinking cap. Battery it is as I first suspected. 11.9 static this morning and 10.5 cranking so I reckon one frost away from death........