Changed fuel filter, odd behavior when priming pumps via VCDS

2011 A3 CBEA, I changed the fuel filter for the first time since buying the car. Everything went fine, but I noticed some odd things when priming the pump. I tried both methods:

1) Engine -> Basic Settings -> Fuel Supply Activation (group 35) When I did this, I could hear the pumps activating, but I got an error message saying "Group 35 not available".

2) Engine -> Output Tests -> Fuel Pump Relay Control Circuit (I think this is the in tank pump) let it run, and I could hear the pump starting and stopping automatically. Then I selected "Relay for auxiliary fuel pump" to activate the pump in the engine bay. After 20-30 seconds it started making a whining sound as though it were sucking air. I went back and ran the in tank pump again, then the auxiliary pump for 5-10 seconds and the sound was gone.

Has anyone experienced this? It seems if you run them separately you run the risk of emptying the auxillary pump.

You did something wrong or changed something. on my 2012 TDI i just loosend all torx bits pulled back the top portion out of the way pulled the old fuel filter out and inspected bottom of canister for any evidence of water contamination or metal fillings (wich if any are found is a bad thing means you need a new fuell Pump) but not in my case all was clear and clean so i refilled the canister near the top with fresh diesel and used a OEM fuel filter put it in slowly and watched air bublles coming off of it a little diesel ran off the top because it was a little over filled but no big deal put back the top head portion screwed all torx screws down using a criss cross pattern until all torx screws were tight to my liking. then jumped in and it started right up as a pre-caution though i did rev it just a little bit for fear of stalling? never did and im sure i didnt need to even do that everyone

thinks oh you need a vcds software tool to prime fuel filters on a diesel i never used one its recommended & Yes the fuel system is under pressure but the key thing here to remember doing once you pry open the top head portion off is not to change anything different or disturb it in any way by that i mean if its full of diesel pull out the old filter & put back in slowly a new filter and leave it full like You found it 1st time You opened it, dont just replace the filter and cap everything off. that's a mistake most guys on here do. You need to fill the canister with diesel same way You found it that's the Key right there but if you didn't fill the canister than you changed something you disturbed it from getting all its fuel now the pump is sucking air. soory i was so long.

Thanks, when I opened the cannister, I pulled the filter out slightly and let it drain completely. The cannister was maybe 3/4 full. Not all the way to the top. I did not refill it either, since I didn't drain it. When I put the old filter in a bucket there was maybe a teaspoon or less of fuel that came out of the filter. I put everything together exactly as I found it. Didn't top it off. Tightened the screws in a star pattern. No metal bits found.

Bill1975 said:

Thanks, when I opened the cannister, I pulled the filter out slightly and let it drain completely. The cannister was maybe 3/4 full. Not all the way to the top. I did not refill it either, since I didn't drain it. When I put the old filter in a bucket there was maybe a teaspoon or less of fuel that came out of the filter. I put everything together exactly as I found it. Didn't top it off. Tightened the screws in a star pattern. No metal bits found.

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Problem is you didn't fill it back up the way you found it. dont feell bad many on this forum have done this too. so because of that the high pressure pump has now sucked up Air have you tried loosening the top off and re-filling it back up to see if maybe it will suck the fuel & start? if not dont keep on cranking & cranking or you will damage the pump get it towed to your shop or dealer that you deal with where there they will run vcds sofware to try and get the fuel pump to suck diesel fuel through the filter rule number 1 in auto repaire when replacing anything is you always put back something the way you found it if not you will find out in a hurry what you disturbed & changed. lol

johnsTDI said:

Problem is you didn't fill it back up the way you found it. dont feell bad many on this forum have done this too. so because of that the high pressure pump has now sucked up Air have you tried loosening the top off and re-filling it back up to see if maybe it will suck the fuel & start? if not dont keep on cranking & cranking or you will damage the pump get it towed to your shop or dealer that you deal with where there they will run vcds sofware to try and get the fuel pump to suck diesel fuel through the filter rule number 1 in auto repaire when replacing anything is you always put back something the way you found it if not you will find out in a hurry what you disturbed & changed. lol

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I don't understand what you're saying. The canister was not totally full when I opened it. I let the filter drain back into the canister, so when I closed it it was the same as it was when I opened it. Anyway, the car still started up and is running fine.

My original question was more to do with the vcds procedure.

If the canister was not full when you opened up the system there is a serious issue that you failed to recognise. Had you filled it 100% you would have improved on the original situation. Maybe not a 100% fix but you have now brought additional aggravation into your life. Start priming!!

miningman said:

If the canister was not full when you opened up the system there is a serious issue that you failed to recognise. Had you filled it 100% you would have improved on the original situation. Maybe not a 100% fix but you have now brought additional aggravation into your life. Start priming!!

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With the filter out, after the remaining fuel drained out of the filter, it was 3/4 full. This level went up after the new filter was put in, though not up to the rim of the cannister. Is this still an issue?

And to reiterate, I did prime before starting the car.

Bill1975 said:

With the filter out, after the remaining fuel drained out of the filter, it was 3/4 full. This level went up after the new filter was put in, though not up to the rim of the cannister. Is this still an issue?

And to reiterate, I did prime before starting the car.

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TDI's fuel system is not forgiving if not full to the rim after changing a fuel filter & caping off but you say you did prime how? using your vcds? dont think its working right for priming but you also say it started up and is running? so im confused? again all you needed to do was fill up the canister to the top with diesel and it would of sucked the fuel no need for any vcds software priming its not rocket science just simple step to do.

johnsTDI said:

TDI's fuel system is not forgiving if not full to the rim after changing a fuel filter & caping off but you say you did prime how? using your vcds? dont think its working right for priming but you also say it started up and is running? so im confused? again all you needed to do was fill up the canister to the top with diesel and it would of sucked the fuel no need for any vcds software priming its not rocket science just simple step to do.

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It was not full to the rim before either. I did not extract any fuel from the cannister. No I did not fill it up with additional fuel. I realize that some people do this, but as I did not remove any fuel from the canister I did not see the point of adding any.

The factory repair manual does not suggest adding fuel even though it says to extract some prior to filter replacement.

I primed two different ways, as described in the first post, both with vcds. I got an error message, even though the pumps were running.

Car is running normally

Might as well close this thread. The OP seems incapable of accepting that he did not follow recommended practice. I dont envy him the problems hes going to have troubleshooting if he wants to get to the bottom of this.

miningman said:

Might as well close this thread. The OP seems incapable of accepting that he did not follow recommended practice. I dont envy him the problems hes going to have troubleshooting if he wants to get to the bottom of this.

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There are no problems to troubleshoot. What problems are you referring to? I followed the replacement procedure from the official repair information that I got directly from Audi. I followed it EXACTLY with the exception that I didn't siphon out 100ml of diesel first.

I primed the pump. The car runs fine.

I'm asking about the vcds procedure for pump priming. Why is that so difficult for people to understand?

I'd just skip the vcds priming. It seems to create more problems than it solves. I never bothered to dig out my laptop for any of the 8 or so fuel filters I replaced. I did like to empty out and refill the canister, but never found anything that justified/necessitated emptying the canister.

turbobrick240 said:

I'd just skip the vcds priming. It seems to create more problems than it solves. I never bothered to dig out my laptop for any of the 8 or so fuel filters I replaced. I did like to empty out and refill the canister, but never found anything that justified/necessitated emptying the canister.

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Thank you.