Light duty diesels today are far more sophisticated than they were only a few short years ago, and diesel service today is correspondingly more complex. Older diesel systems were basically mechanical, and most repairs involved identifying the problem, performing mechanical repairs and replacing any parts needed on-site, or taking the parts to a service specialist who would repair them for reinstallation.
"Today's diesels in lighter duty vehicles increasingly utilize computerized engine management systems and are electronically controlled, and equipped with sensors typically requiring at least a scan tool to identify trouble codes-just like with gasoline engines. And almost without exception, they require specialized training for the technicians who service them-training on the modern systems is absolutely crucial for proper diesel service," notes Al Krenz, director of service for Robert Bosch Corporation, a leading supplier of diesel systems.
With a tradition of providing on-engine/on-vehicle diesel training to independent service dealers through the Bosch Diesel Service Center (DSC) program, Bosch knows a thing or two about light diesel maintenance.
"Much of our work is with fuel systems, and mostly deals with customer driveability concerns," says Chuck Oliveros, a Bosch-trained diesel technician from Williams Diesel Service in Ocala, FL. "Typical symptoms include: no start; hard to start; rough running; and lack of power. We frequently repair, recalibrate or replace injectors and fuel-injection pumps."
TIPS & TRICKS
According to Keith Atkins, senior training author for Clinton Township, MI-based Tweddle Litho Company, and Jim Weiss, training team leader for Tweddle, technicians who work on light-duty gasoline engines can easily make the switch to servicing the new generation of light duty diesel engines. All technicians need to know, they say, are a few new "tips & tricks."
In their work for Tweddle Litho, a major publisher of automotive service training materials, Atkins and Weiss have helped develop service training for International Truck & Engine's Ford Powerstroke diesels, and the new 2.8L diesel being offered in the 2005 Jeep Liberty and Dodge Sprinter. Atkins' first advice for light duty technicians is to become familiar with new emission-control technology:
"The new low sulfur diesel fuel has five to seven times less soot-style emissions than previous fuel mixtures," he says. "We're looking at 3,000 ppm in previous diesel engines to where now we have about 500 ppm.
"The next thing that also helps emissions on diesels are the electronic engine controls," he continues. "Fuel delivery systems are updated with common rail-style fuel injection, where they have computer control over timing and volume. This is very precise, and helps mileage and emissions in diesel engines.
"The last item being used is the particulate trap, which is actually a filter or a scrubber, where the exhaust passes through the system and it removes the soot and the smell from the exhaust," he explains. "They have a couple types: on one you would have to clean that filter or scrubber, and the other type is a new design where they put an electric current through a heating element to burn off particle collection and clean the device."
These issues are sure to become more relevant to fleets with light-duty vehicles, as small "clean" diesels are showing up in growing numbers of light vehicles in the U.S.
"There is a greater acceptance, and part of that is due to fuel prices and improvements in performance," says Weiss. "Keith recalled that his dad had a VW Rabbit diesel in 1981, and the vibration would literally shake the dashboard loose at idle. It got 51 miles to the gallon, but if you were sitting there at a light it was unbearable."
"There are huge improvements in the noise, the smoke and the overall performance," says Weiss. "With the new fast light off glow plugs, you don't have the lag time for start up, you don't get the smoke on start up, you don't get the noise. It's getting to the point that it's indistinguishable from a gasoline engine in terms of what the driver's going to feel."
As for the larger picture, the Bosch Corporation predicts that the light truck market is expected to grow from 3 million diesel vehicles today to 6.8 million vehicles by 2008.
The implications are clear: if you don't have diesels in your light-duty fleet today, you may soon; and if you have some now, you may someday have more. There is plenty of opportunity for diesel service, and with the similarity between today's gas and diesel engines, all a good gas engine technician needs is the proper training.
In designing diesel training materials for Tweddle Litho, Atkins looks first at the vehicle's application to determine "As with any powertrain, the application determines the service difficulty level," he says. "If you have a V6 engine in a small car with a turbo, you're going to have logistical issues with the real estate in there, vs. a V8 diesel in a pickup truck, where you would have a lot more elbow room to perform service.
"Cold starting is an issue with any diesel, of yesterday or today," Atkins continues. "We have better starter technology now, so cranking speed is going to be improved, which is everything to a diesel in cold weather."
Atkins points to glow plugs and intake air heaters as key components in reliable cold-weather starting for light diesels. The technology is newer, but he has concerns that manufacturing cost constraints could counteract any potential improvements to cold starting capabilites.
Bosch's Oliveros has been in the diesel injection pump service business for 23 years. Noting changes in diesel service, he said, "The major difference is pounds per square inch of pressure in the fuel system. At most, today's gas engines run at 80 PSI system pressure. Today's diesel engines run at 23,000 PSI."
"Working around current diesels, you have to use more caution than with the old systems, which ran at 5,000 PSI. You no longer can use the old technique of loosening an injector line to check for a dead cylinder. It could cost you your life, because the fuel would penetrate your skin and get into your blood," Oliveros says.
"People need to be aware of those high pressures," echoes Jim Weiss, "Number one, from a service standpoint, when checking for leaks there are special procedures for that, such as running a piece if cardboard instead of your hand to feel for leaks. You don't want to get that high pressure fuel injected into your skin.
"Dirt or contaminants in the fuel that get through up into the fuel rail can very rapidly decay the parts that are supposed to hold that pressure," he adds. "If those components become worn at their pintle points, it can allow pressure leak-downs which will affect performance. So having a thorough understanding of what the different pressures are at different points of the system, and how to test for those pressures and check for fuel leak-downs, that's going to become an important skill."
"We use scan tools-similar to working on gasoline engines-to determine whether each injector is contributing to the engine," Oliveros observes. "Also, a lot of the sensors, such as manifold absolute pressure (MAP), mass airflow (MAF), air inlet, coolant temperature, and crankshaft position sensors, are all common to gas engines.
"Just a few years ago, we didn't have scan tools but now diesel vehicles give diagnostic trouble codes just like gas engine vehicles. You just can't work on late-model diesels without a scan tool-otherwise you are only guessing. There is no other way to take the readings," Oliveros remarks.
As they develop new training materials, Weiss and Atkins also evaluate the newest tools available to technicians. In the world of light duty diesels, they see diagnostic scan tools becoming better and more valuable to the technician.
"As processors become more powerful, they are also able to diagnose themselves better," says Weiss. "Technicians are very pleased with how much simpler it is to do diagnostics when you have a light on your dashboard and it leads you to a diagnostic trouble code, which then leads you to a service solution to that problem.
"Technicians are still going to have to do basic diagnostics, they're still going to have to be educated in how things work," cautions Atkins. "These scan tools are not a fix-all or substitute for actual knowledge of how the system operates. The scan tool may lead them to something, or they may need to do a static test, like a fuel pressure test, which the scan tool cannot perform. So training will always be required, and it does get more complicated with these newer systems, but in general the new systems are more diagnostic than ever before, and this does for the most part help the technician rather than hinder him."
"Depending on the application, there's going to be a different bleed method to get the air out of the system," says Weiss. "That's a very common issue with diesels: restarting once air has been introduced into the system. I know specifically on the new Jeep diesel application, they've got a primer built right into the fuel filter assembly, so they've alleviated some of those hard start issues that occur after breaking open the fuel system."
"Duramax is the same way, too, where their engines have a primer pump that's on the side of the fuel filter housing to help bleed that air out of the system," Atkins says.
IT'S ALL IN THE APPLICATION
To the experts, the question of maintenance comes down to application. A light vehicle with a newer, smaller diesel engine should not require any more service and maintenance than a comparable vehicle with a gas engine.
"Now you're going to have a larger quantity of oil, and you're going to have a larger quantity of coolant, because the diesel engines require that," says Atkins. "But it's all about being consistent: both will have fuel filters that need to be replaced.
"Larger quantities of coolant and oil in a truck make a substantial difference in cost if you're changing that out all the time, but it all depends on your specific fleet service interval," Atkins concludes. "A lot of fleets like to spend more on maintenance, because they feel they will get more durability out of their engines, and I think for the most part that's true."