Tools to survive and thrive

John Batten takes a look at the art of diagnosis and the one tool to rule them all

Published:  11 June, 2018

My life as a business owner, trainer and technician is an interesting one. I was recently spending some time with a client after a course just shooting the breeze. You know the kind of thing, a cuppa, a cake and an hour just putting the world
to rights.
    
Part way through our conversation Matt proclaimed that I must be “living the dream!” This made me stop and think (something I’ve been told not to do by my wife) about how I am indeed very fortunate to have a career doing something I truly love.

Wading through treacle
Spending my days with like-minded business owners and technicians, helping them drive their careers and businesses forward. What’s not to like about that? Not much, but has my work life always been like skipping through meadow on a sunny day?
    
Quite frankly… No! Don’t get me wrong –  I’m a glass half full sort of chap and regardless of the task ahead I’ll give it my best and persevere until success emerges. However, on many occasions in my diagnostic career it was just like wading through treacle, and therein lies my point. To get to a place where you’re ‘living the dream’ you need wellies! Show me a successful technician and I’ll show you someone who’s great at wading. They’ve just waded long enough to build a versatile skill set along
the way.

The recipe for success
As with most things in life there are essential ingredients. With the right ingredients you’ll successfully avoid the diagnostic treacle swamp and swap this for a faster and more enjoyable repair experience.
    
“What’s this recipe?” I hear you cry. It has six elements that when bought together produce truly remarkable results. They are;

  •  The right technician
  •  The right tools
  •  The right information
  •  The right training
  •  The right practice
  •  The right process


The focus of this month's article being the right tools for your diagnostic survival.
    
I could turn this entire magazine into ‘Johnny’s must-have tool guide.’ However, instead I’ll focus on the
one tool that plays a huge part in troubleshooting success; Enter the oscilloscope.
    
Why am I so fond of this tool? When used skillfully it will quite simply change the way you look at diagnosis forever. I was speaking with Kris Gordon of Pier Garage (one of our training delegates) about this recently. He’s been making some great progress with his fault-finding career and mentioned that use of a scope and some practice has enabled him to “be able to mentally visualise what he should be seeing and the state of the circuit.” This is a sure-fire route to a successful and timely diagnosis. It just so happens that I made a similar discovery in my own career many years ago. Perhaps we’re onto something? But which scope should I buy?

Getting ready to dodge the Bullet
If there was ever a contentious subject it is “which is the best scope to buy?” Wars have been fought over less and in some parts of the world that battle still continues between the diehards in the red camp and the blue camp. I take a slightly more pragmatic approach. Let me ask you a question; How many ways do you have of undoing a 15mm nut? Take a look in your toolbox you’ll find dozens of ways to achieve that task. Why so many options? Different tools for different jobs and in many ways scope choice is no different.

The Search for the Grail
Like Indiana Jones I’ve been searching for the Holy Grail of scopes my whole career and I’m yet to find ‘The One’. What does my Grail scope look like?

  1. Minimum of four channels. Eight would be very cool
  2. The capability to easily build a waveform database
  3. Sufficient hardware specification; bandwidth, record length, samples, waveform update rate etc to accurately display fast frequencies over longer time bases
  4. Great software; A range of triggers, math channels, cursors, ignition analysis etc which will enable me to be creative with my test techniques
  5. Highly portable so I can move quickly and freely around the vehicle without the need to carry a laptop or push a trolley


If by chance you’ve found this illusive tool then I’d be grateful if you’d let me know, until then I’ll continue to use two scopes. A PC based scope for points one through four and a handheld for when portability is key or I need to invert myself in a footwell.

It’s worth bearing in mind that as the “one scope to rule them all” is yet to be discovered then you may need more than one to cover all bases.

I own a Scope – What next?
This is where the magic happens. They key here is to find a little time to practice and look at good waveforms. This, along with the most important questions you’ll ever ask;  “Why does that waveform look that that?" Followed up with a little training or research to discover the answer will propel your career to another level.
    
Take a look at the following example and I’ll talk you through the salient diagnostic points. Waveform 1 is a primary ignition waveform from a BMW 3 series. I’ve made a single connection to switched side of the coil with a full range voltage scale of 500 volts with 10ms across the screen. Let’s take a look at all the diagnostic information we can see from just one connection.

  1. Battery voltage. This confirms fundamental continuity of the positive supply. It is worth noting that as the circuit isn’t loaded at this point, a high resistance in this part of the circuit may not be visible. Another channel testing the coil supply would fix that though

  2. Coil turn on. The ECU has grounded the primary winding and current will start to flow in the primary. Dwell starts here

  3. Dwell time. This is the duration that the primary winding is held to ground. A magnetic field will be building, enveloping the primary and secondary windings. It’s useful to compare dwell across all coils. Discrepancies can indicate primary circuit faults and even ECU output stage issues

  4. End of Dwell. The control unit no longer holds the primary circuit to ground. The magnetic field produced in the dwell phase collapses inducing a voltage in both primary and secondary windings. This can reach many hundreds of volts. Discrepancies here are indicative of primary circuit faults

  5. Ignition burn time. I know you shouldn’t have a favourite, but this is my favourite part of the waveform. Here you can see the effect of mutual induction between the primary and secondary windings. The shape (for want of a better word) in this part of the waveform is indicative of so many variables within the cylinder. Items like plug gap, compression, mixture, cylinder sealing to name but a few

  6. Coil oscillations. At this point we no longer have enough energy to maintain the spark, the event ending with oscillations. This can be indicative of secondary issues

    
All of that and form just one connection. What’s more, I’m not finished yet. For waveform 2 I’ve changed the voltage scale to two volts full range. This enables me to gain additional diagnostic information from the same waveform.
    
Points 7 and 8 are the start and end of dwell, the ramp between them caused by the increase in current within the primary winding (I do love ohms law). Discrepancies here indicate faults within the primary circuit.
    
In summary, one quick connection and eight points of diagnosis that will increase not only the speed of fault identification, but will give additional certainty when it comes to root cause analysis. All this and I’ve only used one channel. Wait until you see what we can do with a few more!
    
If you’d like to know more about how to develop your technical team then call John at Auto iQ on 01604 328500. Alternatively why not attend one of our free online training events. To find out more visit. www.autoiq.co.uk/events




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