Modern tractors, with their vast array of diagnostic sensors and electronics, are hugely complex and incredibly expensive to maintain, or so is the common belief.
However, that view is quite erroneous according to machinery lecturers Vincent McSweeney and Fionn Foley of Munster Technological University (MTU), Tralee Co. Kerry.
Additional skillset
At a recent open day the School of Science, Engineering, Technolgy, Maths, was showing both the teaching facilities and the equipment used in explaining the intricacies of modern machinery to students.
As a rule, in years gone by, these would mainly be various old engines and gearboxes which have been stripped down and reassembled by hundreds of students as they passed through their course.
And while this is still true of Tralee, it has added a further teaching aid in the form of a modest assembly of electronic components which lays bare the essentials of engine diagnostics.
Yet, while this may help dismantle the aura of foreboding and dismay that is often felt by those unfamiliar with digital engine management, the two are keen to stress that a knowledge of how an engine works and is put together is still the most basic and important skill that a mechanic posses.
An engine is still an engine
All those attending an agricultural engineering course at Tralee, at any level, will be introduced to the nuts and bolts on an engine at the campus.
This is one great advantage that the college believes it has over other institutions offering engineering at a higher level – students get a feel for machinery by actually working with it.
While the function and design of an engine may remain much the same, the peripherals surrounding its operation have changed beyond recognition over the last couple of decades, and it is these items which often cause concern among the uninitiated.
There are several drivers behind these advances, but the most important one of late has been emission standards which have stretched the engineering expertise of engine manufacturers in more recent years.
Where the diesel engine is concerned, the most obvious switch is away from the mechanical fuel pump to common rail injection.
Significant change
This move has brought a fundamental change in the way that the fuel is measured into the cylinders; instead of it being managed by altering the volume introduced into the injector, it is now controlled by the length of time that the injector is open.
By switching to electronic control, there comes the opportunity to not only alter the amount of fuel but also the timing of that release, enabling greater efficiency throughout the rev range, rather than just optimising injection timing for one particular situation.
To do this, the engine needs a control unit which can decide upon such matters as how much fuel is to be injected and when it is to be injected.
This is the role of the Electronic Control Unit (ECU) in which there is a huge database of tables and graphs which are referenced by the system for every turn of the engine.
Although the fuelling parameters are set at the factory, they may be changed at a later date by the process of re-mapping.
Keeping the ECU informed
Before the ECU can decide upon the fuelling, it has to be in possession of certain information, which is sent to it by the sensors located strategically around the engine.
Even in the most basic of engines this can amount to a dozen or more feeds, two of the most important being crank position and common rail fuel pressure.
Knowing the position of the crank is essential to injection timing while the injection pressure, as dictated by the pressure in the common rail, is essential for many reasons, not least of which is whether fuel is actually reaching the injectors.
It is this common rail pressure sensor which provides a good example of how an engine’s system for its function can be clearly seen and understood.
Vincent explains that when the ignition is on, it is constantly fed a 5V current, if the engine is not running, a 0.5V current is returned so the ECU at least knows that the sensor is present and working.
When the engine starts and builds up revs, the returned voltage increases and this increase is directionally proportional to the pressure within the rail feeding the injectors.
Diagnostic elimination
At the very basic level, this will eliminate any fuel supply issues and so the technician can move on to examining the engine cycle and its operation with reference to the crank position, allowing the identification of other problems, if present.
To do so, there are tools readily available which can plug into any engine and monitor its activity. In many cases software specific to a brand of tractor isn’t required; the generic instruments and a good working knowledge of diesel engines will suffice in isolating a fault.
The equipment need not be prohibitively expensive either. The university uses a system called Pico, which costs less than €1,000 (plus standard laptop) and may be used with cars and trucks as well as tractors.
Much the same approach can be used for transmissions and other tractor functions, although the university uses this equipment to instruct on how tractor management systems work rather than encourage third-party repair.
Conquer the fear
The big takeaway from the demonstration on the day was that digital engine management systems and diagnostics are nothing to be afraid of, they should be considered a guide through the diagnostic jungle rather than an immediate fix.
They are not taught as a separate subject at the university, instead, they are integrated into the courses where necessary, just as the systems themselves are integrated into the tractors.
Despite the often-voiced concern over electronics making tractors impossible or uneconomic to repair, the lecturers at Tralee set out to show how they may be used to support the servicing of machines rather than displacing the trained mechanic.
They also point out that with there still being a terrific demand for technicians within the industry, the advent of diagnostic repair has yet to put anyone out of work.