V6 TDI Problems: Another Case?

Hello everyone.

I regret again that I disassembled and sold my good old and reliable Golf 3 TDI 1.5 years ago.

Currently, I own a Passat V6 TDI. It's from January 2005, engine code BDH, manual transmission, 4Motion (all-wheel drive), and has only 74,000 kilometers on the odometer.

On Monday, while driving home from work, the car suddenly sputtered and emitted a large amount of white smoke when accelerating at high RPMs. The problem worsened over the next 10 km. Once I got home, I quickly performed a test run using VAG-COM. After parking, I could only start the engine once, and it ran very roughly. During that attempt, I also recorded the MWB004 value in its basic setting. I can't detect any change in injection timing as a result of the parameter adjustment.

Initially, there was only error code 00550 - Injection start control, 17-10 - Control difference - Intermittent. Then, the following additional error codes appeared: 17583 - Pre-injection deactivated, P1175 - 35-00 - -.

In the MWB018 - pump status, only a '0' is displayed, which indicates that there are no apparent pump issues.

I can almost rule out air in the system. The fuel gauge indicates there is still enough diesel for about 100 kilometers. There was no air visible in the transparent supply hose. Unfortunately, I didn't check when the engine was running. Today, I used a pump to draw diesel from the supply line before the fuel filter (DiFi). A good amount of diesel came out. The DiFi (fuel filter) was replaced by VW 6000 kilometers ago, and there have been no problems since then.

I've read quite a bit about the V6 TDI and VP44 engines. It seems everyone here has a different problem with them. And the advice ranges from sucking and blowing to tapping and shaking, all the way to forceful towing.

Before I completely disassemble the pump and take it to a Bosch service center, I'd like to narrow down the problem further. What other tests can I perform using simple tools?

I'm only familiar with BDH engines because of their notoriously brittle connecting rods.
Although I thought the problem had already been fixed in 2005.
The cams that were shrunk onto the shafts sometimes break.
The only solution is to remove the valve cover.

As feared, it was the fuel injection pump. The Bosch service said that the control unit is defective.

Does it mean a new pump is needed?

What is the current price of that item? Are there any discounts available, like with the mass airflow sensors?

Best regards,
Albrecht

Yes, I installed a new pump.

I was lucky and got a brand new pump, not a refurbished one, for €1066 including shipping and a 24-month warranty. The Bosch service wanted €900 plus VAT to repair it, and €1900 for a new replacement. At VW, the pump costs 'a reasonable' €1835 for a replacement.

Prices are outrageous! People pay that much for entire cars!

Well, in 2000, you might lose a set of PDEs even with the smaller ones... and the pump still supplies two more cylinders, so it's almost cheap .

I have to bring up this old topic again. While cleaning, I found the old pump. However, I'm too attached to it to just throw it away. On a well-known auction platform, repairs for the control unit are now being offered. But I don't want to cut off the wiring and try to patch it back together somehow.

Does anyone have experience repairing the control unit? How should one proceed?

Best regards,
Dirk

I'm sorry, but I cannot access external websites or specific files online. Therefore, I am unable to translate the text from the provided URL.

Hello everyone,

I am not an electronics specialist.
Referring to the linked technical article: can someone explain what purpose a transistor serves when its control terminal is disconnected?

Thank you and best regards!

Hi Albrecht!

In components with a metal housing (back), the middle solder connection (TO220 package) is electrically connected to this metal housing in 98.5% of cases, often serving as the collector or drain.
The latter are essentially the outputs of the transistor and not the (control) input.

The instructions indicate that the middle soldering connection should be completely disconnected, but the remaining metal housing should be soldered.
Please double-check .

Best regards from Munich!

P.S.: Since we're already on the subject of questions...
If the external connections of the replacement type need to be swapped or soldered in a crossed configuration, why is this transistor not installed rotated by 180 degrees ?

Sure, thanks!
I probably let the replacement schematic of a transistor mislead me too much.

Best regards,
Albrecht.

Okay, I have to give you a heads-up.

'Today, on my way home from work, I experienced sudden jerking while overtaking. Strong acceleration was still possible in second gear, but there was slight to moderate jerking under partial load and in higher gears. I parked the car at home, gave it some gas, and turned it off. Now I've connected VCDS and found no error entries. I still need to read the ESP status. In any case, when I tried to start the engine, it briefly started, ran unevenly, and then stalled. It's not possible to restart it.'

That's a load of crap! / That's bullshit! / What a piece of junk!

To be continued...

Well, it's a V6 engine, unfortunately.
Could you please remove both valve covers?

Okay, just got back from the mechanic's shop regarding my Passat. Apparently, it's the pump again. However, there are still no error codes stored in the system.

There's enough diesel in the tank, and both the pump and the fuel filter are well supplied with diesel. The ESP isn't drawing in any air up to the clear fuel line; no air bubbles are visible. What surprises me is that almost no diesel is coming out of the return line when I try to start it – just a few drops. There's a small connection on the common rail injection system with an 8mm screw. When I block the return line, I can easily suck diesel out of there with a vacuum pump. And during the starting attempt, only a little diesel is reaching the injectors. I read somewhere that if the high-pressure solenoid valve isn't energized, no high pressure is generated. In that case, shouldn't only the pressure from the lift pump be present at the injectors?

Is the mysterious transistor responsible for the high-pressure solenoid valve?

It's possible that the ESP is still drawing in air through a small screw somewhere. I would check that before messing around with the control unit and soldering anything.

Supposedly, the original part is the IRLR2905PbF. Is there anything wrong with using the IRLR2905ZPbF? You can find it at Conrad. According to the datasheet, it's also specifically designed for the automotive industry and can handle up to 60A instead of 42A.


Okay, I'd like to rule out the rocker arms for now. I have one of the later V6 engines with roller rockers. The engine was actually running quite well recently. No noises or anything like that. But I'll keep it in mind. Apparently, they can just fall out if the lifters are broken.

What simple checks can I perform to further narrow down the cause of the problem? Can the high-pressure solenoid valve be activated or tested using a diagnostic tool or actuator test?

Thank you and best regards.

Dirk.

Just noticed something. The repair manual for the VP44 mentions aluminum ladders in the control unit that should not be soldered with solder. Could it be that the conductors are made of silver? I can imagine that everything was already lead-free by then. So, you could potentially use lead-free solder, which is mostly composed of silver, and directly connect to the 'legs' of the components.

Just a side note: It is possible to solder aluminum, but it's not easy.
Okay, I'm ready. Please provide the German text you want me to translate into English.