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BRING YOUR INJECTORS IN FOR BENCH TESTING 

A phrase that customers often use is, “This is a diesel engine; the problem should be easy to diagnose.” The most accurate part of that statement is that it is a diesel engine.

Certainly, there are some common repairs needed on specific engines that are easy to do, but that doesn’t mean everything else will be easy to diagnose. Owners often think that because diesel engines are now computer-controlled, the technician should be able to hook up a scan tool and immediately see what is going on.

The good thing about electronic diesels is that the technician can link up with a scan tool to analyze data in order to try to pinpoint problems. But some problems may be tougher than your customer — or you — think. Take the diagnosis of an injector issue.

Like anything else, injectors can get tired and become weak over time.

Even though they are electronic, sometimes the mechanical components inside the injector may also become worn, cease to function properly and even fail.

In cases such as these, the scan tool generally will pinpoint the cylinder with the contribution problem.

However, injectors can fail in ways other than becoming just worn out or tired. One of the most common failures occurs when an injector body becomes cracked. When the body is cracked, the engine will not necessarily produce a miss but will cause other problems, which can be even more difficult to pinpoint.

Although the injector body can be cracked, the engine may still run fine but just take an extended period of time to crank.

In addition, the customer may notice some fuel dilution in the oil by seeing that the oil level is rising on the dipstick. When the engine is shut down, the crack in the injector’s body will often cause fuel to drain back from the fuel lines and rails back to the tank. When the leak down occurs, the engine has to spin over for an excessive period of time in order to re-prime the injection system.