Common Rail Lines: Don't Mix 2.7L & 3.0L V6 TDI

Hello,

"In the repair manual for the 6-cylinder common-rail 2.7L and 3.0L V6 TDI engines, it states that the old common-rail lines can be reused if they are installed exactly where they were previously. Therefore, swapping the lines between cylinders is not permitted. Can anyone tell me why this is the case? So far, I have only found one part number for these lines, which suggests that they should all be the same. So why does the repair manual then exclude the possibility of swapping them?"

The reason for my question is that when my Audi dealer installed the new engine, they swapped the lines of two cylinders. From the beginning, the new engine has had occasional strong vibrations when idling and during acceleration, and then it's so quiet that you need to look at the tachometer to see that it's running. I'm now looking for the causes of the vibrations because my has already spent a total of five days trying to find the cause, but hasn't found anything. At least they admit that the vibrations are unusual. That's something, at least .

I was informed on page 3 that the internal surfaces of the lines are coated, and therefore they should not be bent. When swapping them, they might be under different tension, and then parts of the coating could end up inside the injector.

Does anyone have any written documentation about this? Could a coating really peel off and affect the injectors?

It might be due to the cone of the fitting. Once, for example, on cylinder 1, the cone adopted this shape, and now, if it's swapped to, for example, cylinder 2, it could lead to a leak, which is my assumption based on logic. I can't imagine there being a coating inside the rail line, especially considering the pressures of over 2000 bar that exist there. }
So far, I haven't had any problems with engine block swaps, even with older injectors (except that sometimes the injectors are very difficult to remove from the cylinder head), and the fuel rail/lines have worked flawlessly when transferred to the new engine block.

Possible causes include vibrations due to a faulty dual-mass flywheel, a defective injector spraying too much fuel (often audible as knocking and visible in fuel consumption via VCDS), incorrect valve timing, a faulty crankshaft position sensor, or a camshaft wheel that doesn't provide the correct camshaft signal. What error codes are stored in the diagnostic system?

Hi,

Could the injectors have been swapped?
Or were new ones installed that were not registered with their parameters in the MSG (Message System)?

//edit:
Reason is explained here.
Okay, I'm ready. Please provide the German text you want me to translate.

The original engine failed after 117,000 km. The first sign of a major problem was that the coolant level was below the minimum mark in the morning, and when the expansion tank was opened, the coolant sprayed out. Upon inspection by the engine repair shop, it was determined that one or both head gaskets had failed. Because I received 70% of the material cost as goodwill from Audi, the head gasket(s) or, in the event of a crack, the cylinder head was replaced at Audi.
After removing the cylinder heads, the true extent of the problem was revealed: all the cylinders were full of carbon buildup. Due to a special offer on the parts, replacing the entire engine block (block, heads, injectors, intake manifold flaps, turbocharger, and EGR cooler) was cheaper (5,500€ including installation) than replacing individual components.
Only the common rail pump with its associated lines, the alternator, the power steering pump, the air conditioning compressor, the wiring, the sensors, the DPF (diesel particulate filter), and the mass airflow sensor were taken from the old engine.
"Since the installation, the engine vibrates intensely at times, both when idling and during acceleration. On longer highway drives, slight vibrations in the steering wheel cause numbness in the fingers. To make things even more interesting, there are also moments when you don't feel any vibration at all (like this afternoon). Compared to the old engine, the new one is significantly slower. Where I used to reach 4200 RPM, I now only manage 3800 RPM with a lot of effort. The specified values are 4000 RPM and a maximum voltage of 242 V."

At Audi, they have already spent a total of 5 days trying to find a solution, but they haven't found one.
"There are no error codes stored, the new injectors are correctly registered in the engine control unit (ECU), and the idle speed control is well within the specified range - I really don't know where else to look."
Initially, I suspected the motor or transmission mounts, but if that were the case, the vibrations would be constant and wouldn't disappear completely at times.
That's why my question is about the wiring and whether anything could be coming loose and intermittently affecting the injector.

MichaelJ wrote:

Initially, I suspected the motor or transmission bearings, but then the vibrations would have to be constant and not disappear completely at times.

Does the engine have switchable hydraulic bearings?
Is the N144 switch on, and are all the connectors plugged into both hydraulic units?

Let's wrap this up.

After almost two years of dealing with the Audi dealer, who suddenly found three defective injectors at their service center (which were not showing any issues in VCDS), they replaced all four injectors. When I inquired, they stated that the cylinder bores were not damaged. Unfortunately, after the replacement, the engine started to idle roughly, and the EGR valve seemed to be malfunctioning, not knowing whether to open or close.
Finally, I reached my breaking point. With a legal protection guarantee backing me up, I had the engine in my Audi inspected by an expert, along with the Audi mechanics at the Audi center in Koblenz, two days before the spare parts warranty expired.
Result: Three cylinders showed damage to the cylinder walls, poor compression, and signs of foreign objects on the pistons.

I then got a new engine block. Now the engine has been running for two years with the usual quirks, but finally, the vibrations have been reduced to the typical level.
Interestingly, the temporary disappearance of the vibrations was due to the regeneration process. As soon as the particle filter regeneration begins, all vibrations cease, and the engine runs perfectly smoothly.

Hello MichaelJ.

I'm just a layman, and I don't understand the connections right now.
How can a faulty injector lead to scoring on the cylinder walls?
Wouldn't the oil or something similar be more likely to be the cause?

This is the second time that noises have appeared, and the injectors are not included in your list of parts that were replaced during the engine change.

I would appreciate some clarification.
Thank you.
gnash

If the injectors are not functioning correctly, one cause is the dripping of diesel, which continuously dilutes the engine oil and thus reduces its lubricating properties. Another cause is that the injectors no longer spray precisely into the combustion chamber of the piston, but instead onto the edge or even the bottom of the piston. In the area where the diesel unexpectedly impacts, localized overheating of the piston can occur, which can lead to melting.
Both excessive oil dilution and poor spray patterns can lead to scoring or even piston seizure.

Since I haven't found any other possible cause for the double cylinder damage, I assume that I simply had very bad luck, and that the new injectors were damaged during the first engine replacement due to improper initial operation of the engine, and that this caused the damage again.
During my investigation into the cause of the vibrations in the ATM, a service manager at an Audi workshop explained that the injectors in the ASB engine are very sensitive to a lack of diesel. If the mechanic installing them didn't allow enough time for the fuel system to bleed properly, and instead tried to "test" the engine with brief bursts of fuel, this partial dry running of the injectors could have mechanically damaged them. He had repeatedly seen 3.0 TDI engines that, after running out of fuel, would exhibit injector damage shortly thereafter.


There is a constant with the injectors. Two engines, two sets of injectors, but the injector for cylinder 2 is always the furthest in the negative range.

Thank you for the explanation. That makes sense to me!
Best regards, gnasch.