NFU engine no start

[soundlovers]

compression is measured ok
control unit gives impulses to injectors, injectors ok
ignition gives impulses-measured with oscilloscope
gasoline pressure 3.5
may be a problem in the control unit that it ignites at the wrong time - ME745 does not have a cam sensor - it takes information for calculation from the ignition coil or is it a bug in the sw. Or does it not have compression at the first revolutions then yes
everything is determined by the temperature outside below 10 degrees it always starts ok above 10-15 and above the problem is the first starter when the engine is cold, warm engine always starts ok.. I found the same case on the forums, but it was not completed. It is a special fault, maybe someone can help more.

[soundlovers]

1. What we know for sure
Engine mechanics
• Compression 14–15–15–15 bar.
• The engine has power.
• Emissions very good.
• It starts normally in sub-zero winter.
Conclusion: a mechanical engine fault (valves, rings, timing gears stuck) is very unlikely.
________________________________________
Fuel system
Replaced:
• petrol pump,
• petrol injectors.
If the start fails after 8 seconds:
• you can smell petrol.
Conclusion: fuel is getting into the engine.
________________________________________
Ignition
Replaced:
• coil,
• spark plugs.
After the second attempt, the engine starts immediately.
If there was no spark at all:
• it wouldn't start even after the second attempt.
Conclusion: a complete ignition failure is unlikely.
________________________________________
Sensors
Replaced:
• MAP,
• crank sensor.
In the graphs:
• ECU sees rpm.
• ECU counts injection.
• MAP reacts.
Conclusion: ECU knows that the engine is turning when starting.
________________________________________
EVAP
• valve disconnected,
• intake hose plugged,
• no change.
Conclusion: EVAP practically eliminated.
________________________________________
2. What the graphs showed
In the older graph:
Unsuccessful start
• ECU sees rpm.
• ECU counts injection.
• engine does not start.
Second start
• practically the same conditions.
• engine runs immediately.
This means:
The ECU is not "dead" during the first start.
It works:
• senses the crank,
• counts injection,
• controls the start.
________________________________________
3. Today's most important test
Car:
• stood all day,
• about 19 °C.
First attempt:
• 8 seconds starter.
• not even a hint of catching.
After finishing:
• strong smell of gasoline.
Second attempt:
• runs immediately.
This is essential.
________________________________________
4. What rules it out
Theory "you are starting too soon"
Fails.
8 seconds is enough.
________________________________________
Theory "low starter speed"
Fails.
8 seconds should at least catch sometimes.
Moreover, in winter, when the starter spins slower, it starts better.
________________________________________
Theory "poor compression"
Fails.
It would be worse in the cold.
You have the opposite.
________________________________________
Theory "defective crank sensor"
Fails.
ECU sees the speed.
________________________________________
The "immobilizer" theory
Fails.
The second attempt would not start immediately.
________________________________________
5. What fits the opposite
There is one thing that fits almost everything:
The first start does not create an ignitable mixture.
After the first start:
• gasoline remains in the cylinders,
• conditions in the intake change,
• the second start already creates a mixture capable of ignition.
This explains:
why the second attempt starts immediately
why you can smell gasoline
why the problem is greatest around 15–30 °C
why it starts well below zero (the ECU enriches significantly)
________________________________________
6. What I don't like about the ECU theory
The ME7.4.4 / ME7.4.5 manual says that the starting dose depends mainly on:
• engine temperature,
• rpm.
You were right to point out that the ECU does not have any complex "learning" starting correction.
Therefore:
If the ECU calculates the wrong dose
Then the reason must be in:
• input data,
• or calibration.
________________________________________
7. Temperature paradox
The strongest indication in the whole case:
Below zero
it starts perfectly.
A hot engine
starts perfectly.
A lukewarm engine after stopping
it starts poorly.
That is not a normal pattern.
That is almost a textbook problem:
transient enrichment in a certain temperature range.

[soundlovers]

oscillogram failed start

up speed then spark and then injection of the first cylinder....why does it ignite and inject so strangely as if the synchronization is broken? what is the cause?

[soundlovers]

Vehicle: Citroën Berlingo 1.6 16V NFU, year 2006, VIN VF7**************[VIN obfuscated, can be read by forum staff]

Control unit: Bosch ME7.4.5

Fuel: petrol + LPG STAG (the fault is also manifested when the LPG is physically and electrically disconnected)

DESCRIPTION OF THE FAULT

The engine has been showing a very specific starting fault for a long time (approx. 4 years).

Symptoms:

· at outside temperatures of approximately 10–15 °C (spring, summer, autumn) the engine usually does not start on the first attempt after a long standstill

· at temperatures around 0 °C and in frost, it starts normally

· a hot engine starts normally

· if the engine has been stopped for only about 30 minutes, the start is usually normal

· the fault is reliably manifested after several hours of standing or during the first morning start

Procedure of the fault:

· the engine does not start at the first start, the second start immediately

· it usually does not start even after a longer start (about 5–8 seconds)

· after the first attempt, the engine usually starts immediately

· after starting it runs completely normally

· there are no problems while driving

· engine performance is normal

· emissions are flawless

· long adaptation plus minus 4 percent, short-term plus minus 14 percent

DIAGNOSTICS

· no errors are stored in the ECU faults

· fuel pressure OK

· sensor values ​​in diagnostics correspond to reality

· engine temperature displayed correctly

· MAP sensor replaced without change

· crankshaft sensor replaced without change

· ignition coil replaced without change

· spark plugs replaced without change

· injectors replaced without change

· fuel pump replaced without change

· throttle valve replaced without change

COMPRESSION PRESSURES

14 – 14.5 – 14 – 14 bar

ENGINE AFTER START

· runs regularly

· no misfiring

· no smoke

· no error codes

ECU SOFTWARE

· verified at an authorized Citroën service

· ECU software corresponds to the vehicle

· no newer software version available

· calibration was checked and confirmed as correct

INTERESTING NOTES

1. After clearing the ECU autoadaptation, the engine at least once after a whole day of standing, it started immediately on the first try.

2. After the subsequent drive and re-learning of the adaptations, the fault returned the next day.

3. After deleting the adaptations, the engine's behavior was subjectively noticeable.

4. Emergency start on LPG was successful at least once even in conditions where gasoline start normally fails.

5.

OSCILOGRAMS

Oscillograms were taken:

· crankshaft sensor

· ignition coil primary

· ignition secondary

· cylinder injector no. 1

· MAP sensor

· battery voltage

· fuel pump control

In case of unsuccessful start:

· ECU sees engine speed

· injectors are controlled

· ignition system creates a spark

· fuel pump runs

· no crankshaft signal drops are noticeable

QUESTION

Could this be a defect in the Bosch ME7.4.5 ECU itself (for example, in the part of starting dose control, synchronization, internal adaptations or another circuit that does not trigger an error code), or is this type of defect known for ME7.4.5?

Can I send an oscillogram from Texvik, Please read carefully and analyze the text. I will add any necessary information if needed.

Thank you

[soundlovers]

J'ai essayé le spray de démarrage, sans succès. Elle ne démarre qu'au deuxième essai. Voici le graphique PP2000 en fonction du régime moteur : 1er démarrage : échec, 2e : démarrage correct… Que dois-je mesurer si le démarrage échoue ?


Autre photo de l'oscilloscope de vitesse : première injection, deuxième injection…



Peut-être que ça fait tic-tac et que ça s'allume au mauvais moment ?

[PaulC5]

Translation using google

I tried starting fluid, without success. It only starts on the second try. Here's the PP2000 graph as a function of engine speed: 1st start: failed, 2nd: successful start… What should I measure if it fails to start? Another photo from the speed oscilloscope: first injection, second injection… Maybe it's ticking and the light is coming on at the wrong time.