Injector Tips

As light duty diesels become more popular, fleet maintenence shops must be ready with the right training and the right tools.

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.

We Recommend