[urq] I Eat Fuel Pumps - What is Going On

[AF]

Patrick, I do agree that this is vacuum issue. I had a tank collapse on me
2 years ago after I finally installed a well-sealing gas cap. Turned out
the boys at 2Bennett had misplumbed the vent line to a vacuum connection on
the ABZ (the leak detection system). They supposedly fixed this, but I now
believe their bad plumbing job is to blame again for fuel flow issues. Do
you know they said they were not to blame because they did not know the gas
cap had leaked previously, and CHARGED me big money to fix my collapsed gas
tank.

Is it true that an A8 (1997) would have had a gas cap that allowed air in?
If so, is there a gas cap that fits our bayonette style that would have an
air inlet valve? Seems to me looking at diagrams that the leak detection
pump system results in a fully closed vapor system in the A8. The UrQ
meanwhile vented to the charcoal filter when the engine was off but under
load it was connected to the intake boot. A bit more flexible.

So to get this to work, does anyone have a suggestion on how to plumb the
line from the tank vent into the A8 motor to let it "breathe". Or have a
line on a breathing gas cap...

Thanks Patrick and others that responded.

Andrew Finney
1985 UrQ ABZ V8

On Tue, Feb 17, 2015 at 1:52 AM, Patrick Carlier <p.carlier at pandora.be>
wrote:

> Usually these pumps have an internal bypass wich should take care of
> excess flow and / or pressure .
>
> I do agree that if the pump flows to much for the regulator to handle ,
> you'll end up
> withto much much presssure on the fuel rail .
> But that's an other issue , and it should not harm the pump in any way .
>
> Fuel pumps really really hate low pressure on the  intake side .
> It'll kill a pump in "no time " . Btdt got the T-shirt , two of them
> actually .
>
> One cause is a restriction between the fuel and the pump .
> Could be rust in the tank , could be a filter , a flexible hose ....
> anything .
> Pull the hose from the fuel pump , and check if you have a decent steady
> flow .
> No hickups , no hesitations should be seen .
>
> A second possible cause is tank ventilation .
> If somegow you don't get air in the tank , the pump will suck it vacuum .
> I think that is what you're hearing when you say you have a lot of
> pressure in the tank .
> So try this :  , fill the tank only halfway , and do some serious runs
> with the filler cap removed  .
> I bet it'll make a difference .
>
> Best of luck
> Pat
>
>
>
>
> ----- Original Message ----- From: "AF" <afinn1 at gmail.com>
> To: "urq" <urq at audifans.com>
> Sent: Tuesday, February 17, 2015 5:13 AM
> Subject: Re: [urq] I Eat Fuel Pumps - What is Going On
>
>
>  I just found this on a bosch website. Maybe I need to measure my fuel
>> pressure. Maybe I don't need an 044 Racing Pump?
>>
>> *Fuel pump → fuel pressure regulator compatibility*
>>
>>
>> Whilst it has become common practice to fit high flow competition type
>> fuel
>> pumps to standard road cars, it is important to consider whether other
>> system components are suited to this modification. The function of the
>> fuel
>> pressure regulator is to maintain system operating pressure at a preset
>> factory value. This regulator can only do this within its’ nominated
>> return
>> flow specification, an abnormally high fuel flow may exceed the regulators
>> ability to control fuel pressure as it cannot recirculate the fuel back to
>> the fuel tank quickly enough. This situation will result in an abnormally
>> high fuel pressure and/or erratic control.
>>
>> Andrew Finney
>>
>> 1985 UrQ
>>
>> On Mon, Feb 16, 2015 at 8:09 PM, AF <afinn1 at gmail.com> wrote:
>>
>>  I really need the collective wisdom of what's left of the list... a
>>> little
>>> background first.
>>>
>>> when I rebuilt the UrQ I stupidly did not cut open the tank. I mean the
>>> car had sat outside for 15 years. I should have known better. I wen
>>> through
>>> 3 fuel pumps, then I switched to the 034 Motorsport 1 litre sump can and
>>> 040 motorsport in-tank pump with a low pressure feeder pump. I went
>>> through
>>> 2 of those 040 series Bosch pumps before I realized the tank was FULL of
>>> crap and killing pumps. I did everything wrong, I used a 10 micron
>>> pre-pump
>>> filter which was too fine, I tried the original filter-like plastic
>>> pre-pump thing, but last week I finally decided I knew the solution and
>>> stripped all the plumbing out and went back to an aeromotive 100 micro
>>> pre-pump filter, a bosch 044 racing pump and at Patrick's suggestion I
>>> put
>>> a pressure damper on the outlet of the pump. I cleaned and POR15'd the
>>> tank. I cut the filter sock completely off the intake in the tank. I
>>> thought this was the last time I had to mess with the system.
>>>
>>> This weekend at the track, 70 degree day, the pump is buzzing like a hive
>>> of bees and then either overheats or vapor locks after the last run of
>>> the
>>> day. I had to wait for something to cool down before it would run. It
>>> would
>>> start, run, then stumble and die. Lots of pressure in the tank when I
>>> opened the filler cap.
>>>
>>> Can anyone possibly tell me why this pump seems to be dying now after 6
>>> hours of use? What is happening that is killing it? I do have an
>>> adjustable
>>> fuel pressure regulator and 034 tuned it to produce more fuel as I was
>>> running a little lean. Is this an issue of the pump flowing too much
>>> fuel?
>>> It's a tuned ABZ V8 but these pumps should be good for 700 hp right? I am
>>> truly at a loss.... Any help is appreciated.
>>>
>>> Andrew Finney
>>> 1985 UrQ V8
>>>
>>>  _______________________________________________
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>