Fuel filter black and what looks like traces of oil in fuel?

[Ollie795]

Hi guys,

Changed my fuel filter today, from what I could tell it hadn't been changed in about 30K miles, when I poured the fuel out of the filter some of it was clear but then quite a bit of black fuel came out, almost like dye in the fuel.

I know there are 2 issues that can lead to this on the 2.0 PD, the tandem pump and the injector seals.

Is there any way to know what one could be the problem? 

To my knowledge the injectors have never been out, do the seals just fail after time? i'm not loosing any oil that I can tell (stupid black dipstick!) and car seems to run fine other than a lack of power, hence changing the filter, haven't tested it yet though but Idle seemed smoother?

 

[img]https://i.imgur.com/1UKFvLI.jpg[/img]

[img]https://i.imgur.com/hM4sNgh.jpg[/img]

[Ollie795]

I do wonder if anyone actually bothers on this forum...

I’ve been doing some digging and it seems unlikely to be the tandem pump as usually it leaks back into the oil not the other way round.

I’m suspecting the injector seals now, is it common for them to just fail with age? Car has done 127k 

[John C5]

Hi Ollie, I wouldn't worry too much about it. I have a 2008 a4 with the BRD 2.0tdi engine with 230,000miles. It had the injectors replaced by Audi under warranty after they failed and also has had a new tandem pump. I noticed at the last few services that the fuel filter had fuel as you described. The only issues that I had with the car was a bit of a lumpy idle if not fully warmed up with a bit of smoke. This disappeared when it was up to temperature. I have just done a full service on it including belts as Vag Com was showing the inlet cam was 4 degrees advanced. All adjusted correctly now and rough idle and smoke are gone and car running great. I will check the fuel filter at the next service . FYI when the tandem pump needed replaced it caused oil to leak back to the fuel tank and car was very smoky. The tank and fuel line were all cleaned out when the new pump was fitted. Hope this is of help or at least puts your mind at ease. Probably quite common and just isn't noticed as most people don't pour out the contents of the old filter.

[Ollie795]

Thanks for the response John!

I replaced my injector seals yesterday, wasn't too bad a job apart from someone previously destroying the top part of the injector wiring plug on cylinder 1, made it rather difficult to remove without damaging it more! 

Something I was interested in was the wear of the adjuster screw that pushes down on the injector pump, I checked them all for the 180 degree setting that they should be, this is what I found them at:

Cyl 1: 320 deg 

Cyl 2: 320 deg

Cyl 3: 340 deg

Cyl 4: 300 deg

The ends of the adjuster screws were well worn and one had gone through the case hardening, all were replaced and set to the correct 180 deg tolerance, I wonder if this could have resulted in a lower than optimal fuel pressure at the injection point? so having them adjusted properly might make fuelling/efficiency better?

When turning the engine over to check I did notice a sucking/gurgling noise coming from the rocker cover area but was hard to pinpoint where from, I suppose the tandem pump could have a failed seal and be pulling through from the end of the cam shaft? but not sure if this noise is normal as have nothing to compare it to!

I found some slight flat spots on the bottom 2 O-rings that seal the fuel supply from the fuel return sections but that was about all, I didn't realise this being the PPD injectors that the combustion chamber seal is just a very well machined mating surface, I was hoping that the bottom seal had failed but since there isn't one that wasn't the case.

The car does seem to maybe have a little more low end pickup and run a bit smoother, although it's so minor i'm not sure if i'm just imagining it, will have to do a few runs to see if fuel economy is improved! and also I haven't started it other than when first cranking with no fuel in the injectors so will see next time I start it if it starts quicker, usually takes 6-10 cranks of the engine before starting to fire, does that sound more like the tandem pump?

I don't get any smoke, other than when I started after doing the injectors (oil in the bores) so I know it's not burning oil! I've spent enough on this car so am very reluctant to do any more unless it's guaranteed to be the issue. shame as otherwise it's a great car!

[John C5]

Hi Ollie, has your adjustment sorted your power issue. I take it you have no engine management light or fault codes? 

[Ollie795]

Never had any engine lights come up, I'd say there is definitely some more low down torque compared to before, not sure about the top end but might be improved, fuel economy is so far better, where I was averaging 40-42MPG on a 20 mile journey I'm now getting 45-48MPG (have adjusted the car display using VCDS and is within 0.1 MPG tank to tank, also the car is a Quattro so not gona be the best on fuel I know but I was hoping with steady driving it would be up around 50-55MPG on the motorway at 70 with cruise it sits at a terrible 33MPG so I guess something still isn't right

[John C5]

Thanks Ollie, I found that mine averaged between 40 and 50 mpg depending on how it was driven. The cruise control always seemed to get less mpg and my Allroad does the same. My son has the A4 now and he's only getting 35mpg but he'll be using  more of the 170bhp than I did 🤨

[Ollie795]

Ok that’s good to know, I’ve tried adjusting the cams but have only had time to get it set to 0 deg on the inlet and then adjusted the exhaust to get the low idle fuel consumption but apparently putting the inlet to a negative value or positive sometimes can improve power or economy depending on how each engine likes to be set, I would expect my MPG to drop below 40 if I decided to do a bit of traffic light racing and sportier driving but would be nice to think it would stay above that if possible, 33MPG on the motorway still seems poor though...

I still have a strange noise from the turbo, not a failure whistle or anything like that just like a rubbing/gurgling noise, accompanied by a turbo stall noise if I lift of the throttle too quick sometimes, actual boost follows demand very well when checked on vcds so not sure what’s up there if anything!

[John C5]

If the vanes are a bit sticky the turbo might be over boosting which would use more fuel and would be more noisy especially around the airbox. I used Archoil turbo cleaner in the fuel tank when I serviced it. Another job I found beneficial and low cost was removing the inlet manifold and cleaning the swirl flaps and EGR which tend to clog up. I also fitted a new diaphragm to activate the swirl flaps (which was about £25) while I had it stripped down. My inlet sat at -0.7 degrees after I changed the timing belt and set it to audi spec. The exhaust sat at 0.6l/h and it idled smoothly and ran great so I left it at that. It had been inlet +4 degrees and exhaust 0.8l/h before I changed the belt and had a lumpy idle until fully warmed up. Good luck, sounds as if you are getting there with it anyway, cheers John.