The Detail Steps of Checking, Adjusting and Repairing Diesel Injectors

The Detail Steps of Checking, Adjusting and Repairing Diesel Injectors

During the using of diesel engine, there may will be some fault.  

Now if want to rule out the problem and recover the performance of diesel injectors, it need to check and adjust the injectors and its spare parts.

The below are detail steps to show you how to check, adjusting, and repair the diesel engine injectors.

<一>Check the injector nozzle spray

In the range of standard pressure, press the handle with the speed of 60 to 80 times / min to make the diesel injectors spray.

The spray quality should meet the following requirements:

①The diesel should be sprayed like misty, there is no obvious oil drop and oil beam as well as the phenomenon of uneven shades; 

②The diesel should be crisp, when spray, there should be accompanied by crisp sound

③There should not have drip phenomenon before and after the spray.

After injection many times, the place near the nozzle should not have wet phenomenon.

For the injectors with bad spray or needle and valve stuck, we need to replace the new spare parts.

<二>Check and adjust the fuel injection pressure

When check the injector fuel injection pressure, exhaust the air of the oil circuit firstly, then open the three-way switch to make the fuel injection pump provide the diesel for injectors and pressure gauge in the same time. Press the handle (10 to 20 times / min) slowly, when the injector starts to spray, the number on pressure gauge is the injector injection pressure. If it does not meet the requirements, should be adjusted. The adjustment way is achieved by turning the adjusting screw to chang the spring force on the needle valve. When the adjusting screw is screwed, the injection pressure increases and vice versa. After adjustment, tighten the lock nut. Please pay attentionon the adjusting screw, it can not loose. Then recheck again. For the injectors that use the shims to adjust the injection pressure, you can adjust the thickness of the shims, by increasing or reducing the thickness to increase or reduce the pressure.

<三>Check the injector spray angle

Place a sheet of white paper at 150 ~ 200 mm right below the injector. After injection, check the spray angle of the injector according to the oil traces and spray distance onto the white paper.If the normal spray angle is 4 °for diesel injector, it means the the diameter of the traces is about 10 mm.If diameter is larger than 10mm, The spray is large, the injector nozzle hole is worn which should be replaced.For single-hole needle-type injectors, the oil traces should be evenly rounded.For porous symmetrical injectors,the oil traces of each hole should be the same. There is no deflection, scattering phenomenon, spray shape like a regular cone, and the cone angle in line with regulations.

<四>Common Faults During Injector Repairing 

and Elimination Methods

Common Faults During Injector Repairing and Elimination Methods
Valve wear
Failure Reasons:	Fuel is dirty, particles are too big, valve wear fatigue failure
Vehicle Response:	The vehicle can not start or difficult to start
Test Results:	The injector can not injection or the spray is too small
Maintenance Plan:	Replace the valve
Plunger wear
Failure Reasons:	Fuel is dirty, particles are too big
Vehicle Response:	The vehicle is weak and even can not start
Test Results:	Spray is too small
Maintenance Plan:	Replace the plunger mandrel or plunger sleeve
Nozzle hole wear
Failure Reasons:	Fuel is dirty, the particles are too large that make the nozzle hole large
Vehicle Response:	The vehicle has black smoke phenomenon
Test Results:	Fuel injection is too large
Maintenance Plan:	Replace the nozzle
Pre-spray hole block
Failure Reasons:	Fuel is dirty, or there is iron dust block the hole
Vehicle Response:	The engine has sound"clack clack clack", and idling more obvious
Test Results:	No pre-spray
Maintenance Plan:	Clean and check

<五>Check the needle sliding performance
Clean the needle in the diesel, and put it into the valve body. Tilt 45 ° and pull the 1/3 needle valve out. And then release the hand so that the needle down by its own weight decline. The needle valve should down without resistance in 1/3 s, then it is qualified. Grind the valve which not have a good sliding performance but other parts still good when it is necessary. The way is reciprocating rotary the needle to grind with Vaseline oil (or diesel) on needle surface. But do not shoot, and grinding time can not be too long (to prevent excessive grinding).

<六>Check and repair the sealability of the needle
The needle sealing seat surface is easy to have pitting and depression due to the impact and ablation of  high pressure, high temperature gas and the impact when needle closure, so we should check its sealability. We can check on the injector test bench. Adjust the fuel injection pressure to the specified value, press the diesel supply handle, when the pressure rises close to the fuel injection pressure, but has not been injection, observe around the injector needle and nozzle, there should be no diesel dip phenomenon, but allow a small amount of moisture. After several times injection, the nozzle is still not allowed to gather around the diesel or serious oil immersion, otherwise should replace the control valve.
To repair the slightly worn on sealed conical surface--smear a small amount of chromium oxide grinding paste on tapered surface for grinding, but can not touch the needle body guide surface.

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