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Injectors test and replacement

How to test and change faulty injectors. Demonstration step by step on a Renault Clio 2 1.5 dci. Injector return flow test and replacement of 2 injectors (one new and one fully refurbished) .

If your engine fault LED remains on,

Or if your vehicle makes this noise,

or if your vehicle does not start:

you may have an injection problem

Check that the highpressure fuel pump supplies fuel to the injectors

Loosen the high pressure pipe unions 1/2 of a turn

Activate the starter

Tighten the pipe unions through which the diesel flows

The highpressure fuel pump supplies fuel to the 4 injectors

Try to start the engine with brake cleaner

Spray brake cleaner into the air filter intake for about 1 second Start the engine immediately and without preheating the plugs

If the engine starts with the brake cleaner, it is most likely a fuel injection issue

White smoke typically means a worn out injector

Engine vibration at idle means a combustion issue in one or more cylinders

An injector return flow test can detect any leaks inside the injectors

Disconnect the fuel return pipes

The injectors are interconnected by small hoses which return unused fuel to the tank

The return volume is proportional to the leaks inside the injector

Place a plug on the connector of the high-pressure pump fuel return pipe

Connect four hoses of the same diameter (use fuel return pipe, aquarium hose, or windshield washer hose) to the injectors Insert these hoses in an empty bottle

The containers are filling with fuel

The injector no. 1 has a high return flow

The injector no. 2 has a very high return flow

The injector no. 3 has an even higher return flow: it flows almost continuously

After 5 minutes

The return volume of injectors 2 and 3 is more than the 2 others, they must be replaced first

Warning: if you have 1 injector without any flow return, either the electronic control of the injector is defective (no fuel flow into the injector), or the injector is stuck in open position and in this case, do not drive any more with your vehicle because the excess of fuel in the cylinder may burn the piston
Before replacing the injectors, make sure that your fuel system is not contaminated with metal filings

Place a container under the fuel filter and unscrew the bleed screw

If your high pressure pump is very worn, it can generate metal filings that clog your injectors

If you replace the injectors and your pump continues to generate metal filings, you will destroy your new injectors with the small metal particles it produces

If you find filings, replace the pump and clean the entire fuel system (including tank in which flows back injectors) and change the injectors

There are some black particles but no presence of metal filings (bright yellow metal particles) Refit the bleed screw and prime the low pressure circuit by operating the priming bulb

Blow around the injectors with compressed air

Disconnect the injector connectors with a needle nose pliers

Unclip the clip between the High Pressure Tubes

Remove the high pressure pipes

Remove the injector brackets with a Torx bit

Remove the injectors by rotating them while pulling them upwards

If the injector is stuck in its well, you can use releasing spray to remove it

Take back the fire-resistant washers if they remained in the well

Block the opening with a Phillips screwdriver and blow to remove impurities

Clean the injector well with a microfiber (lint-free) Note the reference of the defective injectors and replace them with new ones (or fully refurbished, often cheaper with the same guarantee)

Here are the 2 replacement injectors: 1 new and 1 fully refurbished (internet purchase)

Note on a paper the 16 digits found on injector head

This code can be programmed into the memory of the ECU with a diagnostic tool for optimal operation of the injection

The seller of the injectors and the technical review advocate the systematic replacement of the High Pressure pipes

It is written: "Make sure to change the HP pipes. In case of any doubt, do not hesitate to drain the tank"

In the event of a warranty, proof of purchase of the HP pipes may be required
It's up to you whether you need to change your HP pipes or not

If you choose to refit the old HP pipes, spray brake cleaner and blow compressed air inside pipes

Prime the low pressure circuit by operating the priming bulb

The exhaust fumes disappeared

A new injector return flow test will confirm the repair

The injector no. 1 still has a high return flow

The new injector no. 2 return flow is very low : the return flow of a new injector drips

The new injectors 2 and 3 are OK: their return volume is very low

Injectors 1 and 4 have 250 000 kms: their return volume is more important

The vehicle regained normal operation with the change of 2 injectors out of 4