Differents types of injection

Let's start with some basics. There are 3 common types of injection:

- indirect injection: the diesel is injected in a 'pre-combustion' chamber.

- direct injection: the diesel is injected directly into the combustion chamber. There are 2 mains types:  a system that operates at under 300 bars (for example the Toyota HDJ) or high pressure or “Common Rail”, see below.

- Common Rail injection: high pressure direct injection. Today, this is the most commonly used system (for example the Toyota KDJ series).

Why replace an injector?

Before tackling this job double check if you need to change a single injector or all of the injectors.

Signs that an injector needs replacing can be varied. With a diagnostic readout it can be tricky to determine which injector needs replacing. A good injector injects diesel, but a poor injector still injects diesel, so it’s not that simple.

You may notice drop-outs or hiccups during acceleration, white / gray smoke, a clicking noise (often when cold and which disappears once the engine is warm)… Nothing very scientific, but all of which can point to an injector problem.

In this article, we take you step by step through how to change an injector on your vehicle.

For the purposes of this article we chose to work on a Toyota KDJ 95 equipped with a common rail injection set-up, specific to KDJ engines that can be found among others models in the Land Cruiser range: 90 series KDJ 90 and 95, as well as on the 12 Series KDJ 120 and 125. To be precise, this tutorial is carried out on the 163 hp D4-D version (engine model: 1KD-FTV). These are therefore all “KDJ” 9 Series (so no KZJs which are in indirect injection) and for the 12 Series, only models released between 2003 and 2004.

The vast majority of this tutorial also applies to the Toyota 12 Series version 166 hp (2005 to 2006) and 173 hp (2007 to 2009), but take care to use the injector & seal part numbers specific to these models.  Also be aware that Toyota has issued numerous recalls regarding injector and injector nozzle seals for these two versions. This may include your model so best check first.. Please note, for the 163 hp engine, there is no need to program the ECU with the injector codes as opposed to the 166 and 173 hp models where you will need access to Toyota’s TIS (technical information system software).

The basic steps in this tutorial also  apply to various other 4x4 makes that feature common rail injection.

TOOLS

To change an injector on your 4x4, you need:

. Sockets: 10, 12, 14 and 17

. Ratchet wrench + 10, 14 and 17 sockets

. Torque wrench with 5 to 25 Nm range

. Rags

DIFFICULTY

To give you an idea of the difficulty level of our tutorials, we rate them from 1 to 5.

Replacing an injector on your 4x4 is a level 3 job.

WORKSHOP

1 - The best way to check an injector is to head to your local garage or check yourself using a PC set-up with a mini VCI cable and Techstream software, to check the injector compensation values.

2 - Each injector has a fuel “target” to inject with each engine explosion cycle.

If an injector becomes clogged, it will no longer be able to deliver the same amount of fuel as that of the other cylinders. It will therefore compensate by increasing (or decreasing) the injection volume.

However,  it has an optimal operating range, so it will not be able to do this indefinitely,

On the Toyota 12 Series this range goes from -3.0 to +3.0, beyond that it is no longer fit for use and needs to be replaced.

On a Toyota 9 Series, we haven't found a hard and fast rule. By digging through different technical documents, we found the following:

Max values between -3.0 and +3.0 and off-odds values between -4.0 and +4.0

Another point worth noting: there is also a value not to be exceeded between the minimum and maximum correction between the two “worst” injectors.

For example:

- if one is at -1.3 and the other at +1.7 -> the injectors are good, and the delta between the two does not exceed “5.0” -> all is well.

- if one injector is at -2.6 and the other at +2.9 -> the injectors are good, but the delta is at 5.5 -> out of rating, so we must correct (at least one, to get back below 5.0)!

In our case there was a double problem:

- injector no.2 was at +4.221

- injector n ° 1 was at -1.09

So there was an injector above +4, and the two worst values gave a value of 5.311.

It was a noticeable “clack” when the engine was cold that went away completely once the engine was warmed up that gave us a clue. 

For information,  a failed or faulty injector can cause several problems:

. pollution 

. acceleration hole

. fumes

. and the worst case: engine breakage, if an injector remains stuck in the open position, which can pierce the piston.

3 - Part numbers for Toyota 90 Series:

There are two models of injectors:

- Cylinder 1 and 2 (cylinder 1 is the one towards the front of the vehicle), these injectors have 2 connectors

- Cylinder 3 and 4: thes injectors have 4 connectors

4 - The operation is quite simple on "paper" (a few screws, nuts and a few pipes to remove) but let's be honest, it requires a lot of rigor and you have to take your time so as not to make mistakes.

You will have to remove: the air filter and its box, the intercooler, the intake butterfly valve, the oil filter, the injection hoses, the diesel return hose, the oil breather, the rocker cover , defective injectors, etc ...

So take your time, identify each component, the location and type of each screw and nut.

When you remove the rocker cover, you need to work as “cleanly” as possible: no dust, no foreign objects or liquids. Above all, do not damage the injector tips!

In short, it's a little scary, but all it takes is a rigorous approach, otherwise you will do more damage than good.

5 - We start by removing the air box and the filter to have a little space.

Then we remove the intercooler, starting with these 3 bolts (red circles).

6 - We continue with the last bolts (green circles).

7 - And we finish by removing the big hose that goes to the intake throttle, the two sensors (blue circles) and, last but not least, the two small hoses (yellow circles).

8 - Having removed the intercooler, we can get to the top of the engine to remove the intake throttle.

There are 2 nuts and a bolt to remove (purple circles), it will also be necessary to remove the connector / probe holder (disconnect the vacuum hose which goes to the EGR below).

Then two last bolts (green circles).

9 - Then disconnect the electrical connector from the electric motor (the one that operates the throttle).

No it can be removed by pulling it up.

Then move the wiring harness a bit to free up some space (two bolts between the injector connectors), it will have to be removed later anyway.

Why not  take the opportunity to remove the EGR and give it a good clean !

To do this, you have to remove the two screws (yellow circles), and the last small hose (behind the harness sheath).

10 - All that remains is to lift it out.

Tip: Take the opportunity to look at the intake manifold just below. It won’t do any harm to give it a good clean at this stage.

11 - We move on to the diesel inlet pipes. They are attached in two places: at the top on the injector, at the bottom (under the intake manifold) on the common feed rail (hence the name of this type of injection).

There are four pipes and two small flanges (which hold pipes 1 to 3, and another 1 to 2).

Disassembly is simply done with a 17 mm open-end wrench. To access the pipe of injector no. 4, at the level of the common rail, we have to remove the oil filter.

12 - Once all the pipes have been removed, we take care to protect the threads of the common rail, to avoid contaminating the diesel circuit during the next start-up because it would be such a pain to have done all this for nothing.

It is also necessary to disconnect the connectors at the injectors.

13 - Now it’s time to remove the rocker cover. To facilitate access, we have cleared the wiring harness as much as possible, a few connectors, bolts, and a bracket on the left (where the longest bolt that secures the intercooler is located).

So as not to be hindered, we hung the harness to the bonnet with just a piece of wire.

14 - Next, we remove the four “nozzle holder” gaskets that form the seal between the diesel inlet on the injector and the rocker cover.

Then we remove all the nuts and bolts that hold the rocker cover to the cylinder head.

We also remove the elbow shaped oil vapor recirculation hose which is located on the left.

We carefully remove the rocker cover because it is plastic and its gasket is fragile.

At this time, you must be very careful not to leave any dust or foreign matter so as not to pollute the oil and / or risk damaging a part.

To remove an injector, you must at least unscrew the 4 "collars" that hold the diesel return hose (green circles) as well as the bolts and the injector flange (purple circles).

15 - As soon as you have completed the previous operation, all that remains is to  pull the injector a little (rotating it slightly to help you).

Note: If you change all the injectors, you can make the job a little easier  by completely removing the diesel return hose with the last bolt (blue circle in the previous image).

16 - Comparison of the new and the old injector.

17 - We can now place the new injector into position.

Just before, we double check that there is no foreign body in the injector well.

Position the injector nose gasket (normally aluminum) carefully before inserting it.

Also pay close attention to the tip, it must not hit anything otherwise the injector could be destroyed. So keep the protections on until the very last moment.

18 - Before tightening anything, it is essential to do a blank assembly to validate the alignment of the assembly.

To do this, put the return hose and the diesel fuel hoses back after the injector.

Everything must fall into place without forcing.

At this point, we can put the injector flange back on (pay attention to the direction of the small washer on the bolt, flared part facing downwards).

When putting the diesel return hose back on, the new gaskets are installed.

Hence the advantage of ordering 4 or 5, even if you change only one injector. If you do without these seals, you risk an (invisible) diesel leak in the oil, which will end up polluting, losing lubricating quality, clogging: the strainer, the internal lubrication circuit, etc.

19 - At this point, we move on to reassembly and therefore tightening up to the correct torque settings. This step is, once again,  essential.

The torque settings are as follows:

. Injectors diesel return bolt: 16 Nm

. Diesel return bolt: 12.5 Nm

. injector flange bolt: 21.6 Nm

. rocker cover bolts and nuts: 9 Nm

20 - For the rest of the reassembly, it is basically the reverse of disassembly.

Be careful not to forget a connector, a pipe, a bolt, the oil filter, etc ...

Before firing up the engine, operate the pump on top of the diesel filter head to prime the circuit as much as possible.

The first start of the engine will no doubt be a bit laborious, but it should start up easily. If all goes well, there will be no suspicious noises (pops) or smoke from the exhaust.

If  you do have these symptoms, there is surely a step that was missed and air is leaking into the circuit somewhere ... In this case, you have no option other than to check everything again..

Note: you can use diagnostic software  to check the new injector compensation values. But before that, I advise you to disconnect the batteries, so that the ECU loses the old values and drive a while so that it can “learn” the new values.

PARTS

Find the correct common rail injector for your 4x4:

Article by Alix & Gauthier - blog.pumbaoverland.com

Please note: Euro4x4Parts publishes this information to help its customers but cannot be held responsible for the advice given here and practical consequences therin.

Do it yourself, you'll be even prouder! To help you out, Euro4x4parts shares its know-how and expertise in mechanics through 4X4XPERT: new products, technical sheets, and personalized tutorials... You've got the keys!
And because we also learn from your experiences, your feedback is essential. Let us know your thoughts and suggestions by email: 4x4xpert@euro4x4parts.com

Check out our complete catalogue of 4x4 parts and accessories!

All the photos in our articles are taken on authorized roads or tracks, private land, or during supervised competitions. Let's all do our part to preserve the environment!

Please note: Euro4x4parts publishes this information to help its customers, but cannot be held responsible for the advice given here and their consequences when used.