Opel (Vauxhall) Astra H 1.6 no crank no start, sort of

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liviu2004
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Opel (Vauxhall) Astra H 1.6 no crank no start, sort of

Post by liviu2004 »

I've been called by a friend to have a look to the subject vehicle. Engine has been replaced due to mechanical failure and since replacement, engine failed to start, or if it started, it stopped shortly.
His garage was the 3rd in line for this car diag.

Vehicle details: 2006, 1.6, engine code Z16XEP, semi-automatic gearbox.
Engine ecu was scanned for fault codes, and I received that prior to my visit. His idea was to replace the engine ecu, but I put a hold on the proceedings, as I've seen this before.
WhatsApp Image 2021-05-14 at 12.35.33.jpeg
I thought I saw this before on this forum, but couldn't find anything back on the phone.

Well, we all know for many years what causes such problems. Three big things: spark coil failure or of a bad quality, engine ecu bad ground wire and start motor.

He had one spark coil as spare, we fit it in, no change. Start engine runs for split second, then all modules call CANBUS no comm with engine ecu, and engine ecu does not respond to diag, unless key is off for like 30 seconds.

Second, we fitted a start cable between engine ecu and battery minus. Not smart, as it can cause damage if grounds are bad. A better option is to fit such cable between battery minus and engine body somewhere. Anyhow, no difference, and we actually confirmed later that voltage drop was close to nothing.

Start motor, well, we could hear it while cranking, that is sounded funny, but how to prove it that's the cause? So let's scope something. One channel amp clamp 2000A with auto stop disabled. Btw, what does it mean when red lamp is blinking? Weak battery? Second channel on ecu feed by contact plus.

I've decided to crank the motor direct by start relay, with contact on, but ignition disabled. So with this test I take out of the equation what engine ecu command is.

Let's have a look on the waveform. 6MS and 500ms base time.
test 1.png
test 2.png
Pretty noisy. But there were areas where noise was gone and voltage supply was something better. Interesting.

Let's use the power of pico and zoom in on a peak. Now things become interesting.
test 3.png
Some data:
- lowest voltage 6.4V
- highest voltage 20.5V (where from?)
- voltage rise time 16 us
- minimum current -95A (somewhere along the waveform I've seen -110A)

All this values are to my opinion wrong. Minimum voltage, way too low for an ecu to run? Maximum voltage way above what the ecu is designed for? Even for short time? And I don't know much about electronics, but rise time so short for sure messed up the ecu processor and memory somehow?

And where is the -95A coming from? I think I know this one. As start motor might not be a consumer continuously due to internal defect, it then becomes a dynamo, thus taking mechanical energy from the internal combustion engine kinetic energy and converting it to voltage. And since there isn't any voltage regulator built in, this is how the voltage reaches so big peaks.

I think we nailed the diag. Now the fixes. It's 16:50 and he goes to the neighbors (scrap yard) and comes back with another start motor. He fits that in 10 minutes and you've guessed it, problem fixed. We tried maybe 20 times and engine started flawlessly. And no errors, nothing.

So I took another measurement for reference and look at the difference.
test 4.png
Another happy client will get his car soon.

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PicoKev
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Re: Opel (Vauxhall) Astra H 1.6 no crank no start, sort of

Post by PicoKev »

Wow Liviu,
That is an awesome capture!

Are you thinking that the previous faulty engine was cranked and cranked until it "cooked" the original starter motor, or is it possible that the engine was replaced in an attempt to rectify the fault that you identified that the replacement starter motor cured?

Are you going to be doing a forensic autopsy on the faulty starter motor?

As for the likes of the TA 167 200/2000 amp clamps there are a couple of things to note when using this clamp:
1. The clamp auto-zero's when switched on, so make sure you switch it on BEFORE you put it around a cable, preferably in the general orientation that you intend to use it.
2. It auto power's off after approximately 10 mins, so if you forget to switch it off it saves the battery and a teeny bit of the planets resource's. 8)
When you need to measure for longer periods (eg vehicle / ECU shut down testing). In order to disable the auto power off simply hold the auto zero button when you switch on the clamp. If auto power off is enabled the LED will be green, if it is disabled then the LED is red. If the LED flashes (either red or green) the battery has seen better days and should be replaced. :(

Kev.
Last edited by PicoKev on Sat May 15, 2021 12:55 pm, edited 1 time in total.

liviu2004
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Re: Opel (Vauxhall) Astra H 1.6 no crank no start, sort of

Post by liviu2004 »

Thanks, I appreciate it!

We don't know much about this car, it was dropped off with the keys, so we never saw the owner. But we understood the original engine had a mechanical defect and had to be replaced.

This engine now on the car was fitted in another garage. I assume the donor car was written off because of this issue which no one could trace.

Interesting how, after a miss start, ecu would still log errors, so some parts of it still function, at least the diagnostic part. I assume that in such ecus there isn't a single brain, I think the error detection and triggering is done by an independent part of it.

Unfortunate we had to give the parts back, so I haven't touch the start motor. But can't be anything else then worn brushes and bad commutator. Or a combination with coil contacts arcing?

Thanks for the tip with the clamp meter. I knew about the disabling of the auto power off. I think I have to change the battery indeed, I always carry a spare with me.

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PicoKev
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Re: Opel (Vauxhall) Astra H 1.6 no crank no start, sort of

Post by PicoKev »

Hi Liviu,

Out of interest do you have a comparison of cranking speed between the two starter motors?

I hope you did not think I was "teaching grandma to suck eggs". It was late I had been at work for 12 hours and was tired so just cut and pasted the clamp bit from some of my training material. (Sorry :oops: )

It is great that people like yourself take the time, as well as investing the effort, to produce case studies. There are some really worthwhile examples on this forum and many others around the www. Believe me I know how time consuming the process can be!

To anyone else out there who has something they find interesting and are thinking "Perhaps this would make a good case study" why not have a go and put something together. It does not have to be a 2 hour multimedia fest on something exotic. It sure as heck does not have to be perfect, this is a very convivial forum and no one is going to belittle you.

Case studies also present a really good opportunity to put your thoughts and processes together in one place and allow you to analyse the diagnostic process you employed to get from A to B or in this case from no start to start. I always tell people to think of them as a process of learning and consolidation in your own mind, as well as spreading information and skills to others.

Case studies are a therefore a really useful form of reflective learning that not only benefit the readers but contribute to the creators learning, self analysis and skills set.

Sorry for going on and hijacking Liviu's post :roll: but I am currently in education mode and I do get a bit passionate once I start.

Kev.

liviu2004
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Re: Opel (Vauxhall) Astra H 1.6 no crank no start, sort of

Post by liviu2004 »

Kev, no significant speed difference, something like 8 rpm.
Any piece of info helps, it does not matter if it is copy paste, I'll take it.

I'll have another case study made, this time for a Smart, complete unknown territory for me, but yeah, good shout out there for more case studies.

I am still thinking about this voltage peaks, and kind of thinking along that chemical reaction in a battery is not that fast to react in us? I don't know? If battery cannot absorb amps, then energy equation says that then voltage would go up. P=U*I.

I dare to say, if this car had super capacitors bank for starting, this would of not been an issue. :D
But capacitors would degrade, because insulation material does not like voltage gradients like that.

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