Vorförderpumpe - Passat AFN! | Posts 16+

audi200 wrote:

or do you have any idea how such a difference might arise?

-> Communication/compatibility issue with VAGCOM and the car?
-> Reading error (did you miss a comma?)?

'I don't think it was a reading error; unfortunately, I didn't take a Screenshot. Maybe I will later.'
I also don't think it's a communication or compatibility problem with VAGCOM. It's a Passat built in 1998 and, as I said, the engine code is AFN.

Thanks again to everyone who responded!
This weekend, I looked into some other things that I read about here.
- The pump in the tank is only responsible for balancing the pressure between the individual chambers; it has no connection to the pump's suction line.
- Intake manifold cleaned, but normal deposits were present, nothing that would affect the engine's performance.
- Fuel intake line bypassed (filter disabled), no change.
- I rechecked the LMM (mass airflow sensor) using VAG Com measurement block 000/10, which showed a full load value of 255. I also measured 4.22 volts with a multimeter at approximately 4100 RPM.
- Loading pressure exceeding almost the entire range of 2100 mbar, with a slight overshoot at the beginning.
up to approximately 2250 millibars.
- The other values in the various measurement blocks were also generally within acceptable limits.
at least, according to the comparison list from here.
- Fuel injectors removed and visually inspected; no signs of deposits or anything like that. The only issue remains the significant cylinder deviation readings according to the VAG Com diagnostic tool.
Regarding the fuel injectors, I have a question: Has anyone ever experienced a failure with them?
where performance was compromised without the engine producing excessive soot? In fact, faulty injectors usually become apparent due to significant soot production!

Best regards.
Audi 200.

Hello fellow mechanics,

I need to revisit the issue of the fuel pump and surge tank. I'm getting a fault code 550 (injection timing) whenever the engine is warm, especially after a long drive under heavy load. When I check the supply line and tap on the filter, there's a lot of air in it. I replaced the diesel filter and tightened all the clamps. While bleeding the system, I noticed that I could only draw diesel through the return line; the supply line created a huge vacuum. If I block this vacuum to the tank, no diesel can be drawn through the supply line. If the pump is only filling the surge tank, shouldn't the supply line be completely blocked? Or does the VP44 have something else that's preventing proper bleeding? As far as I know, there isn't a manual valve for this.

Best regards, Manuel.