Soot in fuel filter?

mapleSyrup

Member
Joined
Apr 4, 2025
Location
Whistler, Canada
TDI
2010 Golf Sportswagen
I found a thread saying that if the seals of an injector were damaged blowby could end up in the return fuel line. I was wondering where the blowby would enter the return line? Are they talking about the seals on the outside of the injector?

I heard my aux pump struggling and opened my fuel filter up to find it full of what looked like black soot with little chunks. I just bought the car but believe the fuel filter was changed a couple of months ago.

I drew some fuel from the tank and it's clear and I have a bit of black death blowby buildup on top of my engine. The black death isn't cooked onto the engine top and comes off easy. I've included a picture of what it looks like below.

I swapped the filter and the pump sounds normal but the car runs terribly. I'm thinking dirty injectors. I didn't wait for the car to warm up because I didn't want to further damage the car if it's circulating soot through the fuel system but with the coolant at 25 degrees celcius I got these readings.

Idle Stabilization Injector Quantity Deviation:
0.40 mg/str
-2.19 mg/str
1.29 mg/str
0.52 mg/str





Also wondering if I can take the injector apart and clean myself? I think the turbo is blown, I have the p2015 manifold code and the DPF clogged so I want to see if I can get the car running better before I spend lots of money so if I could even get them to improve a bit with home cleaning it would be useful to know if throwing money at the injectors would solve the problem.

Also what is the best way to flush the return line?

Would changing the seals on the injectors, flushing the return fuel line, cleaning the injectors and putting new seals on the injector plates (https://www.parkautomotorsports.ca/...-audi-tdi-8p-a3-mk6-jetta-golf-fiik-mk6tdi-kt) fix the issue?


I think I ran the car with low oil after the turbo exploded and I wonder if that's what damaged the fuel injector seals.


2010 Sportswagen TDI 244,000km
 
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McGuirk

Veteran Member
Joined
Aug 30, 2012
Location
Florida
TDI
Audi A3 TDI, 2011 Golf TDI 2dr(sold), 2012 Golf TDI 4dr(sold), 2011 Jetta Sportswagon TDI(sold)
The injector plates have an attached seal. You buy the plates to change the seals. If your going to change them you might as well change the valve cover and injector seals/washers as well. If you change the valve cover make sure to go with OEM or you risk the chance of having valve cover leaks because the non OEM covers use the cheap Chinese bolts that are slightly too long and you can't torque the cover down properly. Doing all this will stop all the leaks at the injectors. As far as injector cleaning have you tried additives for the fuel?
Fuel injector install kit
 

mapleSyrup

Member
Joined
Apr 4, 2025
Location
Whistler, Canada
TDI
2010 Golf Sportswagen
I haven’t tried additives I think combustion gases are getting into my return fuel line because the fuel filter had so much black debris in it so I l’m a bit afraid to run the engine for fear of further clogging the fuel injectors.

Do I have to do the valve cover to fix the problem of gases getting into the fuel return line? I’m not so worried about the Black Death on top but my fuel filter is getting clogged. I was going to do all the injector seals that come in the kit but am not sure the car is worth saving instead of scrapping so don’t want to spend a lot of money.


The injector plates have an attached seal. You buy the plates to change the seals. If your going to change them you might as well change the valve cover and injector seals/washers as well. If you change the valve cover make sure to go with OEM or you risk the chance of having valve cover leaks because the non OEM covers use the cheap Chinese bolts that are slightly too long and you can't torque the cover down properly. Doing all this will stop all the leaks at the injectors. As far as injector cleaning have you tried additives for the fuel?
Fuel injector install kit
 

McGuirk

Veteran Member
Joined
Aug 30, 2012
Location
Florida
TDI
Audi A3 TDI, 2011 Golf TDI 2dr(sold), 2012 Golf TDI 4dr(sold), 2011 Jetta Sportswagon TDI(sold)
You could just replace the injector plates, the injector body orings, and copper injector tip seats and see where that gets you. I've never heard of the issue your describing with the return fuel. Id pull the fuel rail and the fuel pressure regulator valve at the end of the rail on the driver side and check for any dirt/debris. The regulator has a very fine mesh filter on it. Also, have you pulled the metering valve on the cp4 pump looking for debris? The fuel temp sensor housing also has a larger mesh filter in it. Not changeable so if it's clogged you have to replace the black T housing as a whole. Here is a link to the line with the housing
Fuel temp sensor housing with line
 
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