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  #21  
Old 8th November 2020, 11:16 AM
Nognar Nognar is offline
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Agreed, will drive it with a Jerry can in the boot and see.

Though it did die on petrol after the alternator/ battery died and before I replaced the pump. It would not start again with the 1/2 tank hence replaced the pump as a precaution. But could well be old pump died and new one had an airlock or no fuel as you say to suck up in the bowl.
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Last edited by Nognar; 8th November 2020 at 11:24 AM.
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  #22  
Old 8th November 2020, 01:01 PM
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Quote:
Originally Posted by MikkiJayne View Post
If not then the new pump may not be seated correctly, or the return line may be outside the pump bowl.
Hello MJ, after lurking on this post and watching the developments, do you think it's worth asking my local garage (the one that fitted my replacement fuel pump within the last year) to refit the pump and pay special attention to this fuel return line? I'm still running out at about 1/3 capacity. I've attached a couple of screenshots from my ELSAWIN for reference.
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Last edited by johnny_quattro; 8th November 2020 at 01:12 PM. Reason: Missed plural of screenshots
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  #23  
Old 8th November 2020, 01:20 PM
MikkiJayne MikkiJayne is offline
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The return pipe is the convoluted piece in the centre of this pic



It needs to be tucked in to the fuel pump bowl. If its left loose it can cause the 1/3rd tank problem.
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  #24  
Old 8th November 2020, 01:21 PM
ainarssems ainarssems is offline
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Low battery voltage can definitely kill fuel pump, I am no expert or physicist but will try to explain best I can. It is a bit counterintuitive as you think lower would not hurt, only higher but I have seen it happen before. The problem is that as volts drop current can increase and too much current can kill it. Now again this is not straight forward as normally current is voltage divided by resistance so lower voltage should be lower current. But the deal is that pump motor actually has very little what what is called resistive impedance so it draws a lot of current at startup but as soon as it starts turning the inductive and capacitive impedance goes up and adds to the resistive impedance so the total resistance goes up and and current reduces. If the voltage is too low to start the pump turning then capacitive and inductive resistance never come into play and pump is stationary with little resistance and a lot of current going through it and eventually it can kill the pump.
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  #25  
Old 8th November 2020, 03:06 PM
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MJ - thanks for the real-life photo, as opposed to the sanitised Audi manual version.
Ainars - thanks for the explanation of the low voltage situation.

From what I understand of a possible shared experience with Nognar's issues mirroring mine (alternator was replaced in my case when it was actually the silver Yuasa battery at fault, and additionally a fuel pump replacement) it's all starting to fit together in my brain.

Armed with that photo, I can now approach the garage with some level of confidence that I might be able to get back to the heady days of being able to use a full tank again. The garage did have initial problems fitting it and was refitted after a complete seal kit was ordered.

Apologies for slight thread hijack but hopefully of some use to Nognar and others.
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  #26  
Old 8th November 2020, 04:21 PM
Nognar Nognar is offline
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I also ensured the return pipe was in the right place. It’s one of the things I checked when fitting the pump for the second time was it poked down into the right place.
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  #27  
Old 8th November 2020, 05:03 PM
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We may both be out of luck then, if my garage did it properly... I remembered that I saw a post by moltuae from a while back and I'm sure he had the whole tank replaced.

Found the post: http://forum.a8parts.co.uk/showthread.php?t=12072

I'm not sure I can stomach that expense right now so I'll keep my 5-litre can in the boot if the garage don't find anything wrong.
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  #28  
Old 9th November 2020, 07:49 AM
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Quote:
Originally Posted by johnny_quattro View Post
I remembered that I saw a post by moltuae from a while back and I'm sure he had the whole tank replaced.
I did. With hindsight (and the right info) it was probably fixable but I'd had enough. 2 different garages, numerous mechanics and I think 3 (or maybe 4) attempts to fix it. I even had a go myself, which quickly turned into one of those 'I wish I hadn't started this' sort of jobs -- Spending a Sunday contorted in the boot, swearing and high on petrol fumes is not my idea of fun.

And to add to the frustration, with every failed attempt to fix it came the testing period and the embarrassment of having the car splutter to a halt, usually at the most inconvenient times, and then having to add a little petrol from a jerrycan to get me to the nearest petrol station.
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  #29  
Old 9th November 2020, 08:53 AM
Nognar Nognar is offline
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Interesting article here on another owner with the fault.

https://www.audizine.com/forum/showt...mystery-solved
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  #30  
Old 9th November 2020, 09:50 AM
MikkiJayne MikkiJayne is offline
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The implication there is that, assuming the pump is seated correctly, that the long bolt simply isn't tight enough and thus isn't compressing the D-shaped gasket and allowing air in to the pump. That would suggest some sort of lubricant is needed on the bolt thread which is compatible with petrol but which doesn't dissolve in petrol.
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