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Kia sorento

Kia sorento 1

Kia sorento

Without keyword

“Don’t be discouraged. It’s a habit.”


In this article we will try to tell you about new diesel engine fuel injection systems and introduce the reader to some issues of repair and diagnostics of the “diesel engine”, the family of the latest developments of the leading manufacturers of fuel control systems (“R. Bosch”, “Lucas”, Siemens ”, etc. .).

What is Common Rail??

Everything is very simple.
The high-pressure fuel pump delivers fuel to the fuel rail, which plays the role of a receiver.
Here the fuel is under constant high pressure of more than 1,000 atm. Opening nozzles does not occur as in a “normal diesel engine” – by a hydromechanical method (from increasing pressure), but electronically – by a supplied signal from the ECU.

The uniqueness of this system lies in the fact that it allows the diesel engine manufacturer to significantly improve the efficiency, power, reduce noise, increase acceleration dynamics.
All of the above applies not only to diesel engines, but also to gasoline cars. These are the well-known D4D and GDI. Each of these systems is good in its own way. But, like many others have their drawbacks.

That’s it about these shortcomings and problems, but only in the “diesel version”, we will try to tell.

As a full-fledged “repair” unit, our workshop exists recently, each person from our “team” acquired his own experience.

And it is worth telling about the experience of the first repair of the fuel system of a 2001 KIA Sorento car. 4DCB common rail engine.

It was the first “Common Rail” that came to our workshop.

Before us, the car visited many other auto repair shops..
And the diagnosis made to this machine was simply disastrous.
And the “medicine” was prescribed in a short and incomprehensible way: “garbage”.
I do not know. I do not understand. And I can not understand.
Just like that: pick up and send “out of sight and away” ?

And the problem was so simple!

But at the same time, it is not entirely clear for the first time. So it is necessary to tell about it in detail. ..

The simplicity lay in the fault itself.

And the difficulty lies in understanding and solving this problem. Here is what really happened:

– The car worked well at idle.

– Well behaved in all modes.

– Fuel consumption is quite satisfied with the owner.

But there was a problem.

If the car was drowned, then it was almost impossible to start it.

That is: it was necessary to remove the inlet pipe or open the air filter cover and spray this combustible mixture into the pipe.

And only after that it was possible to start the engine.

This procedure took place whether the engine was cold or hot. Here in such a terrible state the “sick” arrived to us.

“Finally, our time has come!”, I thought, and with a “smart” look, I picked up a car scanner. In the hope that he will tell me, “where and what hurts the patient”.

But it was not there!

True, the scanner “gave” us a malfunction code for one fuel rail pressure sensor. And when we erased it, we immediately tried to start the engine.

The situation has not changed.
Did not start.

When re-scanning, error codes were no longer found – most likely, it was the “old” trouble code, which remained from the previous workshop.

Consequently, our hopes for a successful solution to the problem, with a simple “wave of a magic wand” in the image of a car scanner, have melted away, and sleepless nights have loomed ahead, in search of technical documentation.

Which we did not have at that time. And what was, was incomplete, fragmentary and not entirely understandable at that time..

In short, no one knew what to do and where to start.

But I really wanted to “DO NOT hit the face in the dirt”.

After all, the owner of the car looked at us as “the last hope.” And really wanted to believe in it. And with all his appearance he made it clear to us. And we understood each other. Clapping hands, we proceeded to our favorite pastime: “Look for a needle in a haystack”.

If you remember, I said that it was our first engine with such a control system. Although we read a lot about them, but as practice has shown, this is not all. And the “haystack” was not so big. The first thing that came to mind was once again to scan the control system according to current data in such modes:

– when the engine is running

– when we try to run it

Knowing that the pressure in the fuel line on the 4DCB engine should be:

– at startup not less than 25MPa,

– at idle 30MPa ,

– at maximum 135MPa,

,- we focused on the study of starting characteristics.

And, as time has shown, we were not mistaken. When the engine is running l, the pressure in the fuel rail was 28MPa from the desired 30MPa.

But at startup, the picture is different: 17MPa from the desired 25MPa.

This guarded us..

After all, the “system is not stupid” and the pressure sensor on the fuel rail is not just an element that we have met before. A membrane with a semiconductor primary converter is located in its body, and there is also an electronic signal processing circuit with a measurement accuracy of up to 2% (at a pressure of 150 MPa).
It is not possible to simply replace this sensor. Check is also problematic. But to consider it faulty, we also could not. Startup pressure loss too high – up to 8MPa.

And this is what was found during a complete check of the entire system for leaks at the time of launch
(all measurements were carried out identically for each nozzle: .

Starter scrolling time 5 sec. and volumetric flask, with a standard of 20mil / lit, a cube.

1st nozzle: 5sec. 8-10 mil, lit.

2nd nozzle: 5sec. 0 mil, lit.

3rd and 4th nozzles the same indicator as on the 2nd nozzle.

Is it “bad” or “good” then we did not know.

It is not possible to check these nozzles for “spray quality” on a simple bench (remember, at what pressure they work).

But it is possible to check for the percentage of leakage. What actually consisted of all further repair of the faulty nozzle. And so it turned out.

When checking nozzles 1 and 2 already at the stand, their leakage rate was as follows:

Nozzle No. 1 – with a sharp press on the stand lever up to 30 MPa, the stopwatch is turned on and the time is checked for the arrow to drop to zero. The result was 6-7 seconds.

Nozzle No. 2 – under the same test conditions: 16-18 seconds, which is twice as much.

But is that the problem? It was still worth finding out.

And then a crazy idea came to my mind. But what if you try to start the car without the first nozzle?
And for this, we took an ordinary nozzle from the MAZ-238 truck and set the pressure to 28 MPa on it. And put it in line with the rest of the nozzles. And the first one was left in place without fuel supply, but with the supply of standard voltage.

And the car started up, sure, but without one cylinder.

Here, it would seem, and found a problem.

Faulty first nozzle.

Starting flow too high.

And the fact that the car was started by improvised means?

So this was explained by the fact that the ignition of liquids based on oils and alcohol, occurs much earlier than diesel fuel. Naturally with great torque. And the pressure sensor did not have time to determine the loss of total pressure in the ramp, but saw only a small fraction of the “overflow” only at revs, when the combustible mixture did not have time to ignite.

All of the above was just a preface. And the most important thing was to fix the malfunction itself. When the owner found out the problem, he was very happy and ran for a new nozzle. But he returned very quickly without her. He said that they requested 1200 cu for delivery.

And the order will be completed within a month, and maybe more.

The fact is that we live in the city of Yakutsk and, as you understand, in many of the benefits of civilization are “somewhat” limited.

Therefore, I had to “do it”.

Unfortunately, not all material was recorded in the photo. This idea did not come immediately and therefore we will post only the material that we have left. And we will devote further narration only to the problem of repairing the nozzle. Since all the other nuances will take even more time, and I would not want to go into their details now.

so , nozzle KIA Sorento 4DCB .
Her “charms and features”.

1. Cruciform guide.

4. Spring locking needle.

5. Multiplier locking.

6. Multiplier sleeve.

7. Hydraulic chamber jet.

8. Ball control valve.

11. Electron magnet.

12. Valve spring.

13. Carbon coating.

In another figure – below (Fig. 2), we present a diagram of the electro-hydraulic nozzle R.BOSCH, which was encountered on this machine, but in the new version of its design – with an additional spring (1).
This spring serves to soften the force directed to the collapse of the ball (5), (Fig. 2). And at the same time it is a locking spring of the multiplier channel (6), Fig. 2. What was our main problem.

1. Valve locking spring

4. Damping spring

6. Multiplier locking
7. Jet control chamber

8. Slot filter

9. Inlet fitting

1 0 – stock (blue color)

11 – ball holder (red color)

12 – ball (green color)

Consider only the problem of the control unit of the electro-hydraulic chamber (Figure 2, close-up).

The difference between these nodes shown in Fig. 1 and 2 is that in the first version (Fig. 1) there is no valve locking spring in the upper part of the nozzle.

Therefore, the main functions of locking and damping that occur during operation fall on one node – valve spring 12 – Fig. 1

And in Figure 2, with the addition of a spring (1), there was a delimitation of the locking and damping forces.

Although in the first version (Fig. 1) we achieve a greater locking force of the spring.

But its performance is good in less “revving” engines.

For example, on trucks of the same Common Rail family .

And when considering small feed rates and large torques, the second option is more preferable (Fig. 2) due to the fact that the distribution of the locking and damping forces of the control chamber has become more stable from cycle to cycle at the time of fuel supply (when the ratio of the diameter of the multiplier to needle 1.2 … 1.5).

But with other ratios of the diameter of the multiplier to the needle, the process becomes more accurate and manageable.

But in our case, we would not want to consider the theory of mass and the relationship of the forces of the system’s speed. And let’s try to figure out the problem of the malfunction itself …

When we disassembled the upper part of the nozzle and studied it in detail, we realized that we would have to deal not with “millimeters”, but with “hundredths of a millimeter”!

Because the diameter of the ball was 1.35 mm, and the diameter of the throttle in the control chamber was 0.23 mm.

But the surprises did not end there. In a more detailed examination of the rod, we saw an end crack on the axis of the rod.

And pretty deep. This is the first.

The second is the bottom of the stem.

The place of contact of the ball holder and a wide stem area. We saw a “broken” dent.

The third threw us into deep thought. Two dents on the cone sleeve of the multiplier from the ball holder. And its contact with the “crater” surface of the multiplier sleeve.

And the fourth circumstance made us not just think, but very much rethink the whole success of the work begun. This is the locking ball itself, fig. 2, green position 12 .

I really wanted to “make” the malfunction, therefore, despite certain costs, to view and study the details of the nozzle, I first bought a large magnifier, then a simple 1 to 100 microscope, and then an electron microscope to fully detail all the objects of study.

And when a complete picture of the whole problem was compiled, then all our ardent enthusiasm and ardent desire to help the “dying” engine – everything was replaced by dullness, compassion for ourselves and complete hopelessness of the situation.

What we had really?

. Broken stock, washed cone and dented 1.35mm diameter ball.

For accuracy, I will say that the length of the rod is 30.27mm, not to mention its strength and metal quality. Its manufacture for us at that time was not possible .

For the simple reason that we did not know who could do this and what consequences it would lead to, if we succeeded in doing it.

And most importantly – can we not violate the supply volume of this nozzle in the entire range of its operation.

And where to find the desired diameter of the ball.

But luck smiled at us. By chance, we drove into our workshop to repair a Nissan “Safari” with an RD-28 engine. When the client heard and understood what problems we have, he decided to help us.

And he said that for him to make such a product is no problem.

So the first question was resolved. It remains to decide: “What to do with the ill-fated ball?”.

And then I remembered that once I came across small bearings, they were used on wood mills. That was the last hope..

And while we were breaking the bearings and choosing the right ball diameter, the first rod sample was already ready.

But when he measured and whether it was compared with the original, the new one was shorter by 0.09 mm.

And still no suitable ball size was found. The “run-up” of the new ranged from 1.18, 1.27, 1.32, 1.45 and up to 2.25 .

1 – the stem of the hydraulic control chamber, which was made to fit the ball size, 1.32 mm, and installed on the machine in the final version. The stock 2 digit 2 was made in the first version, but it turned out to be shorter than the standard by 0.09 mm. As a result, it remained unclaimed. Figures 3 and 4 show one of the samples of the wood milling cutter on which we found a suitable size for the locking ball of the control chamber (Fig. 1, figure 8). The remaining fragments of the photograph are not related to the details of the nozzle. These are metal fragments of the bearing.

And then one crazy thought came to mind. But what if we increase the lower edge of the stem to fit the size of the balls?

And perform it a little with a cone, so as not to completely close the taper of the sleeve of the multiplier. And our new friend had to make the second version of the rod for a ball size of 1.32. And what was the surprise when the car started to start. Already without the help of “dichlorvos” But not as sure as we would like. And when they reduced the adjusting washer under the nut (which tightens the entire structure of the rod and the deffern spring of the control chamber), by 0.01 mm. – then luck began to smile at us!

The car began to start like a real diesel engine. There was no end to joy.

We have not experienced such self-satisfaction for a long time..

So, you can still make these nozzles.

During test runs with the owner of the car and according to the current data on the scanner, we did not see a big difference in the section “fuel injection coefficient by injectors” .

But then they saw the desired start-up pressure – 23MPa. What was 6MPa more than what we saw during the first test (17MPa).

And so our epic with the repair of the KIA SORENTO 4DCB Common Rail injector ended.

I do not want to say that our case is the only option for all failed injectors. But in this case, maybe this was the only true solution to the problem..

Without replacement for a new nozzle.

Unfortunately, we did not save all the material on this work..

But we hope that this material can help someone solve such problems..

It is not always necessary to simply change a part without fully understanding its work. Perhaps someone will say that it smacks of adventure.

Let them talk. It’s their right.

My opinion is: “Do not lose heart. This is a habit! ”.

Well, that’s probably all.

All “sore” questions on the repair of diesel fuel equipment you can ask us in a personal message.

Our inbox,

The necessary afterword
Evokes ordinary human Respect for the “team”, which
did this job. After all, it was much easier and simpler to do as they acted
in previous workshops – “kick off”.

And that’s all, and “the head doesn’t hurt”.

But no, look at how much Labor and Perseverance was invested in this work..
Yes, perhaps, from the point of view of the “academic description”, not everything is “smooth” here.
And the “luminaries,” those people who invented and embodied this engine in metal, are they
horrified by the fact that someone tried to invade their “holy of holies” that
someone tried to change their design on their own.
And get a completely positive result.

Our site will continue to publish similar materials of those people,
for which the words “Diagnostics and repair” are not an empty phrase.
Who are ready to stay awake at night, think, invent and “change their mind” in order to,
to get a positive result and, indeed: “Rejoice” in,
that “they did it!”.

It is on such people – Thinking, Persistent, Purposeful and now holds on
Our modern automotive diagnostics.


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