Nissan Qashqai 2010, 1.5 dci k9k Engine: Difficulty Starting Warm, Increased Fuel Consumption

mirek2610 wrote:

The weird thing is that it starts quite differently. A few times it happened that the cold fire the third time. New glow plugs.

There may be problems with starter, battery, immo + key + ignition , and injectors .

working starter can be verified by lighting "pride". If after the push starts immediately, and the key did not want, it means damage to the starter.

Battery can be checked by switching on all the lights. When the lights dim strongly during start-up, this means weakness aku .

Immo cannot be checked by organoleptic methods. Unless the light is on immo on the desktop, like in my "tadpole". If the indicator light does not come on after inserting the key into the ignition - I cannot start the engine despite the full efficiency of the starting elements.

The same applies the key and ignition . There may be "shaky contacts" and if the electrical circuit is not closed, the motor will not ignite.

The most expensive and the most difficult problem is high pressure pump (pwc), control valves and injectors . For example, they may already be worn out, worn out control valves inside the injections (3 - DELPHI electro-hydraulic injector diagram below) and therefore the engine "capricious" with starting in the least expected moment.

It is necessary then overflow test at idle, which you can do yourself, if you have sufficient workshop equipment https://youtu.be/dpxf4KWcjYQ

Then connect an external diagnoscope to the 16-pin EOBD connector of the motor computer and read a number of current parameters, especially real and nominal fuel pressure, duty cycle coefficients of flow regulator and / or pressure regulator (lines 1-6 in the example table below), injector correction (verses 7-10) pre-injection, main injection and injection (verses 15-17).

The idea is to exclude injectors as guilty of starting problems. They are strategic for the engine because they are directly responsible for take-off and driving, so it is worth excluding them as the first in the circle of suspicion.

I will not discuss the steps listed above in turn. I refer to other threads in which I described in more detail the topic of difficulty starting the engine Common Rail https://www.elektroda.pl/rtvforum/topic3197124.html, https://www.elektroda.pl/rtvforum/topic3211008.html

Kisses KotBury

mirek2610 wrote:

If there was something wrong with the injections, then while driving the car would behave strangely (power loss, smoke from the exhaust or other symptoms)?
Because muj nissan if it fires, then on the road behaves without complaint.

My "tadpole" behaved without complaint on the road. And yet three had to be mentioned control valves except one in injection and wash all in the washer.

The capriciousness of the valves should be explained in such a way that they are very delicate, fragile construction (picture below - comparison to 10 pennies). As a result, they are most exposed among other moving parts to mechanical damage such as pitting, scratches, cracks, etc. As a result, they lose their tightness after some time.

This applies especially to DELPHI electro-hydraulic injectors, which have different modes of operation control valves than BOSCH, SIEMENS or CONTINENTAL. Namely, these tiny valves have special grooves in the neck (orange arrow on the photo above), which are a key element in control fuel injection. Through these gouges, the fuel is directed either to the atomizer, needle and injection channels, or to the overflow.

It is understandable, therefore, that this notch (channel) must be absolutely tight, otherwise the fuel instead of being sprayed and injected, escapes to the overflow into the tank through a leaky (here corroded by corrosion, cracked, scratched) valve.

Hence, sometimes strange symptoms, when the engine suddenly does not want to start after warming up, while in the cold it started flawlessly. Or it suddenly goes out while driving for no reason.

All because the valve is not tight (and this changes under the influence of temperature - here: thermal expansion of metals) and some of the fuel does not go to the injector tips, but escapes to the overflow. The injector is simply not injected enough and the engine goes out a few seconds after ignition, it does not want to ignite, although it is warm, etc.

Photos below show various damages of valves and other elements of injectors that occurred during their operation - I remind you - in very difficult conditions. injectors Common Rail because they are subjected to extreme loads, i.e. billions of times of fuel pressure impact from 200 down 2000 bar ( twenty down 200 MPa ) and more over many years of work. The fit accuracy of moving parts is on the order of microns. As a result, the smallest impurities get between themmay cause their complete destruction or various types of ailments, shown in the pictures below.


I'm not saying that the reason for your troubles are just the injectors. But it is worth in the first step - I emphasize with emphasis - ruled out them guilty or innocent fault.

So it's not about disassembling and replacing them immediately, but checking that they work well.

You should also check in what conditions work. For if they are treated metal shavings through high pressure pump (pwc), sowing with metal chips due to too "dry" fuel - no whip - injectors must fall.

The problem of "dry" fuel is very widely discussed in the forum. I advise you to be interested at the occasion of the checks, whether you have no metal filings circulating around the entire fuel circuit from the tank to the injectors.

If during the inspection of the fuel filter you see metal particles at its bottom as in the photo below, then - as the saying goes - "save yourself who can!". It means that you are refueling "dry" fuel (sulfur-free) and hence the problems in question.


Kisses KotBury

mirek2610 wrote:

Therefore, if it is the cause of injectors if they worked flawlessly in the previous engine.

But what harms you to check them out? Is this such a big obstacle? Just do it and you will have one problem with your head.

if overflow test and injector correction they come out flawlessly, you set them aside as completely functional and proceed to further search. And you still have a black hole.

I emphasize the issue "dry" fuel . Before renovation you could refuel "greasy" fuel, and after refurbishment "dry", because you changed, for example, the station. You have exposed the injectors to damage, where they had no danger before, etc.

Anyway, this is only my opinion, which you do not have to follow. You will do whatever you want and me nothing to do. I just suggest what I would do in your place in the first step. I would make sure and rule out injectors , as well as the entire perimeter high and low fuel pressure , including pwc, fuel regulating solenoids on fuel filter the ending.

I emphasize - nothing needs to be taken apart, disassembled - "non-invasive" methods are enough. At most, you will get stung with stinky fuel, e.g. when inspecting and changing the filter, which I recommend absolutely and that's all.

Kitten KotBury2

Let me remind you what you wrote initially:

mirek2610 wrote:

Computer diagnostics did not show any errors. When the engine starts it works perfectly. In addition, fuel consumption increased from 6.2l to 7.5l / 100km.

It should always cause anxiety injection system, injectors, fuel circuit when the engine starts badly, whether it's cold or warm, that's the first thing. In addition, too much combustion is also closely related to fuel injection . For example, one injector "pours". It makes sense and logical to get rid of this anxiety in the first place.

Secondly, it was not "diagnostics", only reading errors at a standstill using an external scanner. Mechanics do these things "head to head" and call it "diagnostics". Nonsense!

Full diagnostics involves taking the diagnostic laptop to your knees and prolonged driving on the street . Before, you had to erase all errors so as not to disturb the current situation. The result of such driving should be table , which I paste here in every other thread. You have it too, but you don't see it, do you?

I emphasize again - the measure of good operation of injectors and other fuel injection components is not only overflow test . It only answers the question of how it works Mountain injectors, i.e. control valves .

But it doesn't answer the question of how it works bottom injectors, i.e. atomizers, needles, injection channels. This question is answered injector correction (lines 7-10 in the table with notes), this is the third.

In addition, other parameters are important, which I discussed in previous threads, and which you do not know at all (no mechanic knows).

So why do you want to exchange sensors in the dark? On what basis? Guess? As the saying goes, switches falling down ... Maybe arrange with the seller that you first check these sensors on the engine. And only then you will pay for them when they turn out to be an accurate diagnosis? Or pay in advance, but force the promise that if they prove useless, you will give them back, okay?

Kitten KotBury2