Diesel diagnosis involves more – but it’s worth it!
There’s something about diesel engines that inspires awe—their sheer size, power, and complexity.
But modern diesel systems have swapped sluggish torque with modern electronic injection systems, turbochargers, exhaust filters and sound suppression. That means a faster, quieter, cleaner ride.
Rob Ingram, owner of Eldon Ingram, Inc. remembers the old days. “Before emission regulations came in, working on diesel systems was easy. You had a fuel pump that ran straight to lines which had poppet valves that opened up,” he recalls. “They were fairly easy to work on because there was a lot of room under the hood.”
Today’s diesels always have a turbo. “Now the turbo is in the way, and you have diesel exhaust fluid (DEF) systems on all the vehicles, so there’s an injector for that,” Ingram describes. “There’s a minimum of five or six sensors on the diesel systems now where there used to be nothing.”
Tougher emissions standards
“Diesel engine manufacturers have been improving engine capabilities dramatically, all while having to meet tougher emissions standards,” says Mike De Ciantis, Owner, Supertech Diesel Truck Specialists. “This has come at a cost of reliability. In our bays, these emissions systems are adding considerable complexity when servicing and repairing diesel engines. Having dealer scan tools and training is a necessity if you intend on working with diesel seriously.”
This complexity means that it takes longer to work on a diesel than a conventional gasoline motor. “Diesel is a heck of a lot more expensive to repair, especially with all the emissions related items,” says Ingram. “Because of our climate, the diesel exhaust fluid needs to be heated because the fluid will start to gel if it’s too cold. So we have pre-heaters in the diesel exhaust fluid tanks. We’ve had Mercedes SUVs where we had to replace the heater—they’re fairly straightforward, but not something you encounter with a gasoline engine.”
Cramped engine bay
According to De Ciantis, the complexity of the cramped diesel engine bay can be intimidating and unforgiving for most technicians. “To work on a diesel, you must fully understand each system and their operation,” he says. “Many failures lead to chain reactions that cause additional failures. Determining whether a component is the root cause or collateral damage is often not obvious.”
He recommends that shop owners and techs keep up with factory-based training, as well as stay up-to-date with the latest repair methods from the aftermarket. “Many pattern failures on these engines have been addressed with updates, to make sure they don’t happen again.”
Diesel owes its popularity to a variety of reasons. “Fuel mileage is phenomenal,” says Ingram. “The cost of diesel may fluctuate a bit, but it is usually cheaper.” He recalls that on his Dodge Ram, he could drive to Montreal and back, and get 1,100 kilometres before he was about 100 kilometres from empty.
Car won’t start
Servicing diesel requires a few different approaches. “You need to change your fuel filters every second oil change or once a year,” says De Ciantis. “Clean diesel fuel is critical.”
Ingram adds that a quality filter is paramount. “If you end up with a plugged fuel filter you’re asking for trouble.”
He recalls when Mercedes vehicles had a plastic bladder under the spare tire for DEF. “Now there’s a tank, and it needs to be kept full,” says Ingram. “The emissions coming out of the tailpipe are drastically changed when there isn’t DEF in the system. When the light on your dashboard comes on to tell you to fill it with DEF, if you don’t fill it, you have only so many key cycles left – and then the car won’t start, and you have to tow it to the dealer.
“It’s not going to shut down when you’re driving it, but when you shut it off, it may not restart. That means you have to fill the DEF, reset the monitors using a scan tool to reset the parameters, and then clear trouble codes to get the vehicle to start again.”
Fortunately, there are many scan tools which can assist in the servicing of diesel. “There are a lot of sensors on these systems now, whether it’s the injector nozzle for the DEF or oxygen sensors, and all those sensors are expensive,” notes Ingram. “But they’re no more difficult to repair, whether light duty or passenger vehicles, because every scan tool has data now for diesel vehicles. The technology has evolved so we can scan the data, go through the system and dissect it with the scan tool, compared to what we used to do mechanically.”
De Ciantis offers his customers some important tips, including filling up at high volume fuel stations. “Moisture in the fuel can cause catastrophic damage,” he notes.
It’s also key to run a fuel conditioner. “Don’t buy one from the corner store, ask a reputable injection shop for their recommendation,” he says. “These recommendations are not universal due to climate, etc.”
Replacing oil on time, with the proper oil and factory filter is essential. “Make sure you are watching your oil level between filters,” De Ciantis says. “Some DPF systems can introduce diesel fuel into the crank case. An increasing oil level is an indication that fuel is diluting your engine oil, which can lead to engine damage.”
And finally, he encourages customers to get out on the highway and drive their truck, loaded, if possible. “Repeated short trips that don’t allow your truck to reach operating temperature can clog your DPF and EGR systems.”