Replacing/Inspecting Fuel injectors

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Introduction

Applicable to all engines (H4D and H4Bt or M281 E10 and M281 E09)

Tutorial shown on an H4D but entirely applicable on an H4Bt. The only difference between the two is the injector's orientation on the fuel rail.

H4D and H4Bt's injectors are different (see wiki).

Step 1 Accessing the engine hood

Replacing/Inspecting Fuel injectors, Accessing the engine hood: step 1, image 1 of 1

Open the trunk.
Put aside the trunk carpets.

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Step 2 Acessing the engine compartment

Replacing/Inspecting Fuel injectors, Acessing the engine compartment: step 2, image 1 of 1

Unscrew the 6 T50 screws by hand or using a wrench and a socket.
Lift and put aside the engine hood.

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Step 3 Disconnecting the fuel injectors

Replacing/Inspecting Fuel injectors, Disconnecting the fuel injectors: step 3, image 1 of 1

Disconnect the fuel injector's connectors.

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Step 4 Disconnecting the fuel supply hose

Replacing/Inspecting Fuel injectors, Disconnecting the fuel supply hose: step 4, image 1 of 1

If only inspecting of the fuel rail/injectors: skip this step and do not disconnect the fuel hose: the fuel ramp can rotate freely and the hose is slightly flexible. This will avoid to flush the fuel rail's fuel volume to do this routine check.
Fire hazard: fuel may run out of the hose and/or the fuel ramp ! Please take the necessary precautions to avoid any incident.
Undo the security clip using a flat head screwdriver.
Disconnect the fuel supply hose.
Reinstallation: respect the security clip's orientation, indicated by a foolproof.
Make sure the hose is properly reconnected by pulling firmly on it. Someone found themselves on the side of the road because their hose had come off.
A poorly connected hose seems to cause symptoms identical to clogged injectors. After my hose accident, my engine became smooth again as I initially expected after cleaning the injectors (much less vibrating).

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Step 5 Extracting the fuel rail

Replacing/Inspecting Fuel injectors, Extracting the fuel rail: step 5, image 1 of 2

Replacing/Inspecting Fuel injectors, Extracting the fuel rail: step 5, image 2 of 2

Unscrew the 2 8mm bolts holding the fuel rail.
Pull straight the entirety of the fuel rail upside. You may rock the fuel rail slightly to help it get unstuck.
The second image show what a clean H4D's (Deka/Siemens) fuel injector looks like. The 6 holes are visible and free.
If one or more injectors where to be cleaned, please refer back to step 4 to disconnect the fuel rail entirely.

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Step 6 Removing an injector from the fuel rail

Replacing/Inspecting Fuel injectors, Removing an injector from the fuel rail: step 6, image 1 of 1

Undo the clip holding the injector to the fuel rail by slightly spreading it and then sliding it.
Pull the injector to extract it. You may need to do gentle rocking/rotating motions to unstuck it: the seal may be dry do the extended contact with fuel.
Reinstallation: make sure that the clip makes a square shape, like it was when you were undoing it. You may need to pull out the injector slightly to pull the clip back perfectly in the slot intended for this.
Reinstallation: torque the 2 8mm screws at 10 N.m.
Reinstallation: ideally, you should replace the seals. Lubrify (by a hint) the seals using a finger and some silicone spray to both help the reinsertion of the injectors on the rail and when reinstalling the assembled fuel ramp on the intake manifold.
Refitting: Clean the injector wells on the intake manifold (holes into which the injectors are inserted) to ensure a tight seal.
Avoid getting any debris into these holes, as they open almost directly into the valves. Any debris sucked into the engine can create catastrophic consequences.
Improper installation of the injectors can cause an air leak, which can be very harmful!

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Conclusion

The engine should only vibrate very gently at idle when you place your hand on the intake manifold if the injectors, MAP sensor and throttle body are clean.

The 3 cylinders must also vibrate equally.

Driver's seat: Engine vibrations in the seat should be very light at idle.

One other person completed this guide.

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