Diesel from a different direction

Frank Massey looks at diesel servicing from another angle...

By Frank Massey |

Published:  08 July, 2019

I want to discuss diesel servicing from a totally different direction, compared with the usual angle. Let’s also start from a different angle, compared with the usual view. Consider this; Servicing is a failure prevention strategy.  Conducted in accordance with the operating environment there should theoretically be no failures. Please note my careful choice of words, operating environment. Manufacturers always have and are still marketing their vehicles with inappropriate servicing regimes.

The political focus is one based on a relatively short warranty period and tailored to business or lease company requirements. In my opinion, service intervals should reflect the operating environment rather than fixed values such as time or distance.
The very activities established as suitable by the VMs fall woefully short of actual requirements. Vehicle owners are, I believe, misled by a whole group of agencies with regards to vehicle ownership and responsibilities.

I also think the possibility of cradle-to-grave ownership is closer than we like to acknowledge. You rent or lease a vehicle over a two-to-three year period with all maintenance inclusive. At the end of the rental period the vehicle is exchanged with a consecutive end to end contract. No responsibilities for repair or servicing.

With this in mind, how should we approach diesel servicing given the problems with premature component failure and excessive emission issues?

Detailed knowledge
Let’s assume we have a new customer. Our first responsibility is to understand how they operate the vehicle and their aspirations and value of operating and investing in what is the Holy Grail, i.e. reliability.

Detailed knowledge of driving style, traffic environment, driving distance, fuel quality, should have a direct influence on how servicing should be applied. This would be a unique profile for this customer.

  • Conduct a visual safety inspection, both static and raised

  • Conduct a test drive. This may include data gathering via the serial interface

  • EOBD offers several critical opportunities for evaluation. default flags, continuous and non-continuous faults, condition not met flags, and not least, warm up cycles, distance driven and time since last active regen cycles

I would suggest a maximum nominal value of 300 miles between regen cycles. Examine the oil condition thoroughly and if necessary, have it analysed for fuel-based contamination.

Next, we move onto a more focused non-intrusive evaluation of live data. It is worth noting the following components.
Mapped cooling

  1. MAF values at idle with and without EGR, pay attention to MAF response time vis EGR. A sticking or leaking EGR will slow the maf response, this should be prompt with little or no delay
  2. Quite often the rather nondescript fault code “condition not met,” preventing active regeneration, fails to identify the specific component or function requirements. For example, during passive and active regeneration cycles, combustion temperatures can be subtly influenced if you increase engine load through activation of the heated seats and heated mirrors. I’m also tempted to suggest that coolant control modules and thermostats will also assist in this endeavour

Mechanical engine condition

  1. Mechanical engine condition can be established with a simple range of tests:
  2.  Relative compression
  3.  Cranking current and rotation speed
  4.  Injector balance or correction
  5. Comprehensive picture

At this point we should have a pretty comprehensive picture of the vehicle operating conditions.
Good fuel quality, and the correct choice of filtration and oil are critical if premature turbo failure is to be avoided.
At ADS we do conduct engine flushing as part of the service package. Carefully examine the fuel filter before discarding. I believe EGR valves and injectors do have a finite life without waiting for failure to occur first.
We find that rubber control hoses and intercooler circuits deteriorate causing restriction or leakage so look carefully at adaption or correction values. These should be in the region of:

  •  + - 2% normal
  •  + - 5-10% concern
  •  + - 10-20% serious condition

If you discover correction, then there is a fault requiring attention.

SCR systems
SCR systems require further consideration. Problems are common with injector nozzle fouling, dosing pump failure and no additive. Pump pressure can be checked with a gauge, and injectors can be tested with a range of existing injector test benches.

The implications of this list will add a great increase in cost, as technicians we should focus on requirement and process not cost! The customer owns that responsibility.

Related Articles


©DFA Media 1999-2020
Terms and Conditions