How To Repair Denso Common Rail Injector-3
Fuel pump dispensing volume adjustment and the reasons for the uneven distribution

How to repair denso common rail injector-4

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.

How to repair denso common rail injector
How to repair denso common rail injector

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).

STEP 2.2 – Solenoid & Solenoid Valve Assembly

How to repair denso common rail injector
How to repair denso common rail injector

Fit the half ball valve into the solenoid valve stem and ensure that the flat face of the half ball valve is visible and level with the stem. DO NOT INSERT THE VALVE STEM INTO THE VALVE SEAT IF YOU CAN SEE THE SPHERICAL PART OF THE HALF BALL VALVE (Fig 22). IT MUST BE THE FLAT SIDE (Fig 21).

How to repair denso common rail injector
How to repair denso common rail injector

The half ball valve should stay in the valve stem when turned over and inserted on the valve seat. Once the valve stem is in position ensure it is free by rotating it (Fig 23).

Place the fuel calibration shim on top of the injector (Fig 24)

Next, insert the solenoid spring shim and solenoid spring into the solenoid and carefully fit the solenoid onto the injector, ensuring that the spring seats in the centre of the valve and hand tighten. Once hand tight, tension the solenoid assembly to 10‐12 NM (Fig 25).


STEP 3.2 – Nozzle and Cap Nut Assembly

Re‐position the injector assembly in the jig with the solenoid towards the bottom.

How to repair denso common rail injector
How to repair denso common rail injector

Insert the command piston into the injector body with the main shank machined with grooves towards the solenoid end (Fig 26).

Next insert the nozzle opening pressure shim and the spring into the central injector bore and then insert the pressure spindle on top of the spring with the smaller diameter facing the nozzle needle (Fig 27.)

Insert the locating dowels into the sealing face and place the injector over them. Place the (new) cap nut over the nozzle and screw down until hand tight (Fig 28).

Ideally some kind of injector clamping rig should be used to unsure alignment of the nozzle, if you can find something or manufacture anything suitable to hold the body. The arrangement pictured below (Fig 29) features the Stanadyne Injector Aligning Tool (Part #29617). An injector aligning tool was not used in this exercise and no operational problems were experienced, however it would be better to use one if available to minimise the risk of misalignment or breaking the dowel pins.