This article gives detailed instructions on replacing the fuel injectors in a BMW vehicle with the N62 8 cylinder engine. Even though we used a 2005 645ci to perform this repair, this article can be applied to any vehicle with the N62 8 cylinder engine including V8 5,6,7 and X5 series vehicles with minor modifications to the repair steps.
A BMW N62 fuel injector replacement will help cure a rough running V8 engine.
The BMW N62 V8 engine first made its appearance in the 2002 E65/E66 7 series sedan. It was the successor to the M60/M62 engine that was found in all of the V8 5,7 and 8 series cars from the 1990’s and early 2000’s. The newly developed N62 engine was a major advancement over its M62 sibling featuring a light alloy design, variable intake manifold, and Valvetronic. These advancements helped reduce fuel consumption and emissions while increasing power and torque.
The BMW N62 engine has eight flow controlled fuel injectors located on the top of the engine, just below the main wiring harness. The fuel injectors are managed by the N62’s Engine Control Module (ECM) which determines the quantity of high pressure fuel that is injected into the cylinders during engine operation. They are simply electronically controlled valves that open and close a plunger, allowing atomized fuel to spray into the intake manifold ports where it mixes with air for combustion.
The number one cause of fuel injector failure in the N62 engine is contamination. All fuel, no matter the brand or grade, contains small amounts of dirt and water. After years of operation these contaminates find their way through the fuel system and into the injectors causing them to clog. Hydrocarbon deposits from engine combustion also can build up on the tips of the injectors, restricting fuel flow and causing the injectors to malfunction. Fuel injectors can also experience mechanical failure.
Like all engine parts, fuel injectors have a definitive life span. They do not last forever and eventually need replacement. The classic symptoms that you require a BMW N62 fuel injector replacement are: rough idling, poor acceleration, engine misfiring, poor fuel economy, hard starts and engine stalls. The BMW Repair Guide recommends that the fuel injectors in your N62 V8 engine be changed every 100,000 miles to keep the engine running optimally.
A BMW N62 fuel injector replacement is deceptively easy with one caveat – the main engine wiring harness must be partially removed. Several of the harness’ wires are a challenge to disconnect and may require jacking the front of the vehicle on some V8 models to remove them. We give full step by step instructions below along with a parts list for your convenience.
1. Fuel Injectors (required) – The BMW N62 fuel injectors are precision calibrated parts that will give years of service. Avoid cheap aftermarket “generic” fuel injectors…they don’t last as long as OEM quality ones. We give you several excellent choices based on your brand preference and budget.
Unfortunately before you can remove the fuel injectors from the N62 V8, the main engine wiring harness must be cleared out of the way. This is because the wiring harness is mounted on top of the fuel rail making it nearly impossible to access the injectors. The main engine wiring harness is split into a right and left side. They are basically identical except for the front connections. Take your time and use patience when disconnecting the main wiring harness…some of the electrical connections are difficult to access. Please be aware that you may have to get under the front of the vehicle to access two of the right side harness connections that plug into the AC compressor and the vacuum pump.
- Before starting this repair, disconnect the negative terminal to the vehicle’s battery. Since you will need to remove part of the engine’s main wiring harness to gain access to the fuel injectors, not disconnecting the battery could cause catastrophic damage to sensitive electronics.
- Remove the microfilter housing covers by releasing their metal retaining clips. Use a 13mm socket to loosen the plastic mounting nuts. Remove the hood switch from the right microfilter housing cover. Remove the covers from the vehicle.
- Remove the microfilter housing locking cover by raising its plastic tab and sliding it free.
- Remove the rubber hood gasket from the microfilter housing.
- Using a 13mm socket, loosen the rest of the plastic mounting nuts securing the microfilter housing to the body of the vehicle.
- Use a T20 torx bit to remove the two screws anchoring the lower microfilter housing to the body of the vehicle. Grasp the lower microfilter housings and remove from the vehicle.
- Use a T27 torx bit to remove the upper engine cover.
- Unplug the mass air flow (MAF) sensor.
- Disconnect the vacuum line from the intake boot.
- Unsnap the intake muffler lid. Loosen the hose clamp on the intake boot where it attaches to the throttle body. Grasp the lid and the boot and remove them from the vehicle.
- Use a T45 torx bit to remove the four bolts anchoring the strut brace to the body of the vehicle. Removing the strut brace will give you the extra space needed to move the wiring harness out of the work area.
- Using a T30 torx bit, remove the bolts securing both the left and right wiring harness to the top of the engine. Remove the engine cover brackets from the vehicle.
- The following steps should be performed on both the left and right sides of the wiring harness….
- Unplug the Valvetronic motor on both sides of the engine.
- Use a small flatblade screwdriver to release the plastic tab securing the ping sensor plug. Unplug the ping sensors on both sides of the engine.
- Unplug the fuel injector control wires on both sides of the engine.
- Unplug the intake camshaft position sensors on both sides of the engine.
- Remove the side engine covers.
- Unplug the eccentric shaft sensor on the rear of the valve covers on both sides of the engine.
To finish clearing out the main wiring harness, the front connections on both sides of the engine must be disconnected as well. Several of the connections are challenging, most notably those on the right side of the engine that are attached to the AC compressor and the vacuum pump. We found it easier to raise the front of the vehicle to remove these connections.
- Starting on the right side of the engine, disconnect the thermostat sensor.
- Follow the right solenoid control wire down to where it connects to the two solenoid control valves on the front of the right timing case. We found the easiest way to unplug the valves is by depressing the metal locking clip with a long flatblade screwdriver and pulling them free with a pair of long nose pliers. Mark the plugs with tape so you don’t get them mixed up during installation.
- The last two front connections on the right wiring harness are the vacuum pump and AC compressor. These two connections are notoriously difficult to access from the top of the engine…we find it much easier to disconnect them from the bottom of the vehicle.
- Begin by locating the AC compressor plug. Reach up with your hand and disconnect. Sometimes using a long flatblade screwdriver helps like shown below.
- Finally, locate the vacuum pump plug. Once again, reach up with you hand, depress the metal locking clip, and pull the plug free.
- Pull all the wires out of the engine and fold back gently out of the way. Lift the right wiring harness and bungee cord out of the work area.
- Moving to the left side of the wiring harness, unplug the throttle body by depressing its locking tab and pulling it free.
- Next, unplug the water pump sensor.
- Unplug the fuel vent valve sensor.
- Unplug the right solenoid control valves using the same technique used in step 2 above to remove the left ones.
- The final front wire is connected to the back of the alternator. This wire is extremely difficult to remove…we strongly recommend leaving it connected. Fortunately the left wiring harness can be cleared out of the work area if you disconnect the exhaust camshaft sensor in the next step instead.
- Locate the left exhaust camshaft sensor. It is mounted on the rear of the valve cover on the left side of the engine.
- Unplug the exhaust camshaft sensor. This can often be tricky…we found the easiest way is to squeeze the plug’s locking tabs in GENTLY with a pair of long nose pliers with one hand while prying the plug off with a flatblade screwdriver with the other hand.
- The left wiring harness can now be cleared out of the work area. Carefully move it to the center of the engine as shown below and bungee cord so it doesn’t move.
The BMW N62 fuel injectors are located on the bottom of the fuel rail. The entire assembly is pressed into the intake manifold and held in place by four mounting bolts. Sometimes the injectors can become stuck inside the intake manifold and are difficult to pull free. Use patience during this step. We strongly urge our readers NOT to try and pry the injectors out if they are stuck…you could severely damage the intake manifold or valve covers.
- Before removing the fuel rails, the fuel pressure will need to be released. Locate the Shrader valve on the right side of the fuel rail and remove its cap. The Shrader valve is the same as the valve used to inflate your tires…simply press down on its stem with a small screwdriver to release the pressure. Have a rag ready to catch any fuel that may spill out.
- Locate the fuel line on the left side of the engine. Remove its plastic locking collar, then retract its black plastic release. Pull the fuel line apart…have a rag ready to catch the small amount of fuel that will drain out.
- Use a T30 torx bit to remove the four bolts anchoring the fuel rail to the intake manifold.
- Starting on the left side of the engine, grasp the rear of the fuel rail and pull it free from the intake manifold. If the fuel rail is stuck, gently wiggle it back and forth while pulling until it releases as shown in the following images.
- Remove the fuel rail from the right side of the intake manifold.
- Remove the entire fuel rail/fuel injector assembly from the vehicle and place on a clean bench.
- Starting with the first fuel injector, depress the metal locking clip and unplug the injector’s electrical connection.
- Remove the metal clamp that secures the fuel injector to the fuel rail.
- Grasp the fuel injector and remove it from the fuel rail. If the fuel injector is difficult to remove, try turning it back and forth while pulling until it comes free.
- Check inside the fuel rail to make sure none of the injector o-rings came off during removal. If they did, remove them from the fuel rail with a metal pick.
- Remove all eight injectors from the fuel rail.
Installing the new fuel injectors and reassembling the vehicle is very straightforward with no special procedures. Be sure that the new injectors are firmly seated in the fuel rail before installing the metal retaining clamps. We have provided a detailed reassembly checklist below with necessary torque values for your convenience.
BMW N62 Fuel Injector Replacement – Reassembly Checklist
- Install the new fuel injectors in the fuel rail. Replace their locking clamps and electrical plugs.
- Install the injectors back into the intake manifold. Use the palm of your hand to make sure they are firmly seated in the manifold.
- Reinstall the four fuel rail mounting bolts and torque to 10.5 Nm (8 ft-lb).
- Reattach the fuel line. Install its plastic locking collar.
- Reinstall the cap on the Shrader valve.
- Starting with the left side of the wiring harness, plug the exhaust camshaft position sensor back in.
- Plug the left solenoid control valves back in.
- Plug the fuel vent valve back in.
- Plug the water pump sensor back in.
- Plug the throttle body sensor back in.
- Move to the left side of the wiring harness, plug the vacuum pump back in.
- Plug the AC compressor back in.
- Plug the right solenoid control valves back in.
- Plug the thermostat sensor back in.
- Moving back to the top of the engine, plug both the right and left eccentric shaft sensors back in.
- Replace both of the side engine covers.
- Plug both the right and left intake camshaft sensors back in.
- Plug the left and right fuel injector control wires back in.
- Plug the left and right ping sensors back in.
- Plug the left and right Valvetronic motors in.
- Replace the top engine cover brackets. Install the wiring harness mounting bolts and torque to 10.5 Nm (8 ft-lb).
- Replace the strut brace and torque its four bolts to 25 Nm (18 ft-lb).
- Reinstall the intake muffler lid. Make sure the hose clamp is secure.
- Install the vacuum line back on the intake boot.
- Plug the mass air flow sensor back into the intake boot.
- Install the upper engine cover.
- Install the microfilter housing.