how to repair denso common rail injector-3.


Solenoid assembly

Resistance checks should be made to the solenoid. The specific resistance measured will depend upon the type of injector and should be compared to a new unit. The resistance recorded on the particular G2 injectors that we tested was approximately 0.5 – 0.7 Ohms.

Obvious signs of any damage to the outer casing or splits/cracks on the electrical connector should be observed. Check for erosion/corrosion of the electrical terminals and ensure that the inner surface of the solenoid is clean and free from dents etc (Fig13).

Ensure that the solenoid spring is in good condition. It may be a good idea to check and record the length against a new one.

Solenoid Valve and Half Ball Valve assembly

Check the condition of the solenoid valve assembly , paying particular attention to the half ball valve face and the seat inside the valve stem. The flat face of the half ball valve is responsible for sealing the control chamber, so it must be in good condition with no erosion or wear. These components are best inspected under a microscope. Check the conical seat that the ball seats on inside the valve, as well as the valve stem for any signs of wear, scratches and erosion (Fig 14)

Renew both components if there are any abnormalities or doubt on their condition (both available from Diesel Distributors).

Valve Seat and Retaining Nut

Inspect the valve seat for erosion and wear (Fig 16). As with the ball and valve assembly, thisis probably best viewed under a microscope or other magnification equipment. If there are any marks across the seating area that would suggest a sealing problem – renew the valve seat (available through Diesel Distributors).

Inspect the sealing face of the retaining nut for signs of erosion and wear (Fig 16).

Due to the very fine tolerances involved in CR injectors, lapping of the sealing surfaces of these components is not recommended. Any attempt to lap the surfaces should be undertaken with the utmost care and with the use of VERY FINE lapping pastes.

Command Piston & Injector Body

Check the piston for scoring and wear marks along with the inner bore of the injector. If there is considered to be excessive scoring or wear on either component, then the unit will more than likely be scrapped (Fig 17). The piston should be clean, free from scoring and move freely inside the injector bore with no ‘snagging’ or tight spots.

Nozzle Assembly, Pressure Spindle and Spring.

Guidelines for inspecting the nozzle assembly can be considered the same as for any conventional nozzle. Check for excessive wear or scoring on the needle shank and seat and renew the nozzle if necessary. (Genuine and non‐genuine nozzles are available from Diesel Distributors, depending upon application and availability). Check the spring for condition and the spindle for excessive wear on the spring seat.


When re‐assembling any common rail components, clean practices should always be observed and the utmost precaution should be taken to avoid any contamination of the components before and during assembly.

WARNING ‐ The torque values mentioned in the following procedure are a SUGGESTED VALUE based upon our experience and NOT Denso specification.

STEP 1.2 – Valve Seat Assembly

Mount the injector in the holding jig and place the 2 locating dowels into their bores on the top face of the injector (these dowels are larger in length and diameter to the nozzle locating dowels). Ensure that the valve seat is the correct way round before inserting it into the injector. The bore on the underside of the valve needs to be aligned with the bore hole on the injector face (Fig 18 & 19).

Using the 3 pronged socket, insert and hand tighten the retaining nut into the injector with the sealing face towards the valve. Screw the guide over the socket, ensuring that the socket can still move, but with maximum support from the guide and tighten to 70‐75 NM (Fig 20).