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

Sat Feb 28 02:56:35 PST 2015

The V8 gas cap was used on any post 1987 car . 
Rougly i'de say it ws used on all the cars that have  the the carbon cannister system . 
I'm afraid I don't have any , so I can't tell if its vented or not ,  but I doubt it . 

EU Urq's never  had the carbon canister system apart from maybe the last ones . . 
Instead they had an "egg" shaped check valve on top of the fuel tank .  
Little grey plastic thingy . If you shake it , you can hear the ball rattle inside . 
It was designed for two purposes . 
Allow air into the tank when fuel is used . 
And to vent pressure from the tank , fi when parked on a sunny day  
fuel vapors would rise the tank pressure and the tank can'thandle that . 
Vent/breather line  was routed simply trough the chassis , a white nylon tube . 

Then came legislation to prevent fuel vapoours entering the environement . 
So later cars had 3 lines from the tank to the engine , the third being the vent wich was now conected to a carbon cannister . 
The carbon cannister stores fuel vapours in active coal , rather then venting them to the air .
If the engine runs , the carbon cannister is sonnected to the intake vacuum allowing the stored fuemes to be burned off .  
and allowing he active coal to regenerate  . This is done by the blue electrovalve(s) 

Now I haven't got a car with this system , so I can't tell for sure , 
But either the cap has to be vented , or the elctrovalves must somehow open  the vent line to ambient air 
when the engine is running . Certainly not to the engine vacuum , wich would make things worse . 

I have done  a 7A conversion on a 1986 Coupe quattro . Wich is also an efi engine in a cis car .  
I kept the original tank vent system , with the egg shaped check valve . 
The connection from the carbon system to the intake was plugged . 
The carbon cannister was dumped . 
And the electrical connection was insulated . 
Car's running fine for 7 years now . 

So maybe that's the easiest way for you to fix your problem .

P/N for the check valve is 893201753 . 
It's called gravity valve . 
Make sure it's not mounted sideway's or upside down , it's designed to work in the vertical position only . 

I've tested this valve , and if I blow in it , it oens with little pressure . 
If I suck it , air enters easily without any depression . 
That is exactly what the tank/cis system needs , unrestricted flow . 

Sorry about the long post , got carried away a little :) 

Pat  

----- Original Message ----- 
  From: AF 
  To: Patrick Carlier 
  Cc: urq 
  Sent: Friday, February 27, 2015 11:27 PM
  Subject: Re: [urq] I Eat Fuel Pumps - What is Going On

  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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