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When you Should Replace the Fuel Injector of the BMW

Author: German Auto Specialist
by German Auto Specialist
Posted: May 08, 2020

During the service and maintenance process of your BMW, the fuel injector is generally moved from the intake manifold to the combustion chamber. The fuel injectors are generally used for dispensing the fuel, if it is damaged, then it will cause drivability issues in your BMW such as the electrical problems or fuel problems. The following points define the signs that will help you to determine the time of replacing the fuel injectors of your BMW.

Heat soaks

When the engine of your BMW shuts off, the fuel injectors undergo to soak the heat. In this way, the fuel residues evaporate in the injector nozzle and leave waxy olefins behind it. Due to the closed engine, the cooling air unable to flow through the ports as well as the no fuels flow through the injectors to wash it.

Eventually, the low mileage, short drive cycles, increased heat soaks and these deposits can build up and clog the injectors. If the BMW is used primarily for a short trip driving then the deposits may build up faster. In the hot locations, the injector clogging from the heat soaks because of the high above the location of the intake manifold plenum. Due to their placement in the head, the heat soak can affect the direct injection injectors.

Fail in the balance test

If you suspect that the fuel injector of your BMW is clogged or malfunctioned, then determine the disable injectors through a scan tool. By considering the voltage changes of the O2 sensor, you can easily recognize the leaking injectors and dead injectors in your car.

Each injector of your car is energized to monitor the drop in fuel pressure and that would be tested through an electronic injector. When opened, each injector should drop the same amount of fuel. The normal pressure drop of the fuel injector indicates a rich condition that could be caused due to the stuck plunger or the worn pintle.

Turbo issues

Generally, in the turbocharged engines, the dirty fuel injectors will cause dangerous leaning effects that may lead to engine damages. Whenever the engine of your BMW is under boost at a higher rpm, then it needs to deliver all the fuels of the injector to the engine.

If the fuel injector of your BMW is malfunctioned or dirty and unable to fulfill the engine demand, then the fuel mixture will lean out and cause detonation of the injector as well as the engine. Eventually, the engine may cause higher leaning than the normal exhaust temperatures and failed the turbo.

Fluctuate fuel trims

The fuel calibration curves in terms of the powertrain control module are completely based on the OEM testing by using a new engine. The fuel pressures have generally specified a range for the engine and allow the short-term and long-term fuel trim to adjust and compensate for variance in the fuel pressure. It also used for maintaining the proper amount of air/fuel ratio within a certain limit. When the fuel injector is energized, it becomes clogged with fuel varnish deposits and fails to deliver its normal dose.

Due to the weak fuel pump, leaky fuel pressure regulator or the plugged fuel filter, the fuel pressure injector drops below its specifications level. As a result, the air and fuel mixture is too leans and cause misfiring in the cylinder.

Longer cranks

The injector leak is generally caused in your car due to the rail to lose pressure. When the car is idling, it will cause longer than normal crank because the rail will need extra time for pressurizing. Thus, the normal crank time for the diesel common rail injection system is around three to five seconds which is similar to the common-rail pump to build the fuel pressure.

In a fuel rail pressure threshold, the cranking is generally occurring in around 5,000 ps, but in a common rail system the cranking is occurring at 5,000 psi at idle and can reach up to 30,000 psi at a wide open throttle.


When you will notice any of the above-defined symptoms in your BMW, then make sure that the fuel injector of your BMW is damaged and need immediate attention. So, bring your BMW for inspection by a BMW professional to rectify the issue and make it useful for a longer period of time.

About the Author

German Auto Specialist provides expert German auto repair in Simi Valley, Moorpark, Thousand Oaks, Westlake Village and Newbury Park for over 23 years. Having ASE certified & factory trained technicians with latest diagnostic tools and equipment.

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Author: German Auto Specialist

German Auto Specialist

Member since: May 05, 2020
Published articles: 5

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