In a Cummins engine, the injectors will not be actuated by the controller until the fuel rail pressure reaches the threshold. Normal common-rail systems will operate at 5,000 psi at idle and can reach up to 30,000 psi at wide open throttle. This is how long it will take the common-rail pump to build fuel pressure to the “threshold.” The threshold for cranking is when the fuel rail pressure reaches around 5,000 psi. When the leak down occurs, the engine will have to spin over for an excessive period of time in order to re-prime the injection system.Ī normal crank time in a common-rail injection system is usually around 3 to 5 seconds. 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. 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 body is cracked, the engine will not necessarily produce a miss but will cause other problems, which can be even more difficult to pinpoint.Īlthough the injector body can be cracked, the engine may run fine but take an extended period of time to crank. One of the most common failures occurs when an injector body becomes cracked. However, injectors can fail in different ways, other than becoming just worn out or tired. In cases such as these, the scan tool generally will pinpoint the cylinder with the contribution problem.

Even though they are electronic, sometimes the mechanical components inside the injector may also become worn, cease to function properly and even fail. Like anything else, injectors can get tired and become weak over time. The misfire is generally associated with a loss of power and no unusual smoke. The most common injector issue is that the engine produces a cylinder misfire.

It may be tougher than your customer – or you – think.

But take the diagnosis of an injector issue. 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.

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