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    Thread: Help! I need a gas tank schematic for my Mk1 GTI.

    1. 10-15-2007 02:13 PM #1
      Yes, for all you Dane Cook fans, I did just use the word schematic in a sentence.

      All - I am having fuel delivery challenges for my 1.8T powered 1984 Rabbit GTI. I've dropped my tank to have it cleaned and investigate whether my interior fuel lines were faulty / not connected.

      It turns out that they are connected and seem to be in good shape (bummer as I thought that this would be the cause of my fuel starvation issue). I did discover a loose wire mesh filter sitting in the bottom of the tank. It is not the one that sits in the baffle box.

      I need help trying to figur out what this cylindrical filter is and where it is supposed to go.

      A Mk1 fuel tank schematic (better than the one in the Bentley manual) would be great.


      Modified by michaeldarr at 3:12 PM 10-24-2007


    2. 10-15-2007 02:14 PM #2
      Alternately, if anyone has picks of a dissected Mk1 fuel tank, I would appreciate those too.

      Thanks,
      Mike


    3. 10-15-2007 06:45 PM #3
      If your referring to the basket like filter that goes in the middle of the plastic baffel then it just slides in to the similarly sized space in the center of the black baffel. i used a pair of needle nosed pliers to get it back in. Mine just slides in and seat rather firmly in place.

    4. 10-15-2007 06:47 PM #4
      also might want to try technical forum. i found good help there when replacing my mk1 tank

    5. 10-16-2007 12:50 AM #5
      Hi - It is not the blue wire mesh filter that sits in the black baffle. That is firmly in place. (Although, I did remove it with needle nose plyers for inspection. I've already put it back.)

      I'm speaking of another cylindrical wire mesh filter (this one is black) that is rolling around in the bottom of my tank. I need to know where that one is supposed to go.


    6. 10-16-2007 12:51 AM #6
      What did you do to replace your tank? Did you use another factory tank, an aftermarket replacement or a fuel cell?

    7. 10-16-2007 03:05 AM #7
      Just an FYI,

      on my '77 I noticed when replacing the fuel pump that fuel was not coming out the nipple on the bottom/side of the tank... despite the fact it had a gallon or two in it, at least. I used a plastic drain snake thing to clean out the line and then fuel came spurting out, the line was obviously previously clogged. Despite this the car had run all along!

      -Rob


    8. 10-16-2007 04:12 PM #8
      The tank is out and I will have it cleaned by a radiator shop. I will do as you suggest and perform a little "rotorutor" to the in-tank lines prior to having the tank cleaned.

      Now, can anyone tell me where the other cylindrical filter is supposed to go?

      Thanks.


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      10-17-2007 12:41 AM #9
      You should give a better descrption of the filter you want us to identify,... or show us a picture.
      Does it look like the one on the left:

      If you are going to jab stuff into the exit hole, don't poke a hole in the rubber plug (on the right) it keeps all the junk on the bottom of the tank from being pulled into the fuel line.

      Another lovely pic for the curious:


      I don't think I have a picture of my fuel tank/line cleaner. It's a fuel pump with a clear plastic fuel filter before it, preceded by a curved piece of metal tubing. I pull the tank screen and use the fuel pump to "vacuum" the fuel out of the tank/ through the filer and back into the tank.

      In a real bad case where the gasser had sat for years, the filter wasn't in it's perch (someone probably had the great idea of using air pressure to clear a fuel line back to the tank).
      All those years of crud got pulled into the fuel line so using the "tank vac" I pulled fuel out of the tank, through the filter and pumped it back into the engine bay,... backflushed the whole fuel line.
      It took around 7 hours to get the fuel flowing clean again,... counting the time we spent eating pizza with the pump vac backflushing the system


    10. 10-17-2007 09:34 AM #10
      I'll work on getting a picture posted of the mystery filter. It look similar to the one in your picture of the baffle box. However, that is not it as my baffle box filter is still installed in the baffle box.

      This car has been in the family since new and we have no record of anyone working with the gas tank prior to me dropping the tank last weekend.

      The pictures that you provided of the baffle box and of the cutaway tank are very helpful.

      Now I have a much better idea of where the various in-tank lines go and where the rubber hoses are located.

      Does anyone happen to know if the aftermarket tanks come with the baffle box set-up?


    11. 10-21-2007 02:02 PM #11
      Thanks to all who have replied to help me figure out my fuel delivery problem.

      The tank is out and I have pulled the bafflebox filter and also fished out the mysterious second filter. This second filter was rolling around in the base of the tank. I've inserted a picture below of both filters.

      As you will see, they are the same type of filter. The black one is very similar (if not identical) to the one shown in an above posting but the blue one (the one that was installed) has a far more open weave. The blue one flows much better but does not filter small particals the way that the black one would flow.

      The part number on the black one is: 810 201 511 E
      The part number on the blue filter is: 431 201 511

      Once the installed blue filter was out, I noticed that the diaphram looking part also shown in an above posting (beside the removed baffle box) seemed off-center. I touched with a thin screwdriver and it became apparent that this part was seriously deteriorated. I removed it with a set of surgical hemostats (good thing I liked the game, "Operation" as a kid) and pulled out the sorry looking item shown in the below picture.

      My question for the forum is, what does this diaphram-looking part do and must I have it installed for the gas tank pick-up to function properly? If so, I am in bad shape as the tank will need to be cut open to make this repair.

      Please let me know.


    12. 10-21-2007 02:17 PM #12
      Forgot two things...

      1. Even though the car has been in the family since new and we have no record (or memory) of someone monkeying with the tank (other than me) it is obvious that someone dropped the black filter into the abyss while putting in the blue filter. It's either that or my Westmoreland Rabbit GTI gas tank was assembled on a Monday!

      2. I've re-read the above posting (the one with pictures) and see that the diaphram that I am having issues with is a "cap" that keeps trash on the bottome of the tank from being sucked into the pick-up tube.

      My hypothesis is the deterioration of this cap means that my pick-up tube is sucking from the bottom of the tank rather than from within the baffle box. When I take a high-g corner to the right all of my fuel sloshes (techical term) to the driver's side of the tank and away from the baffle box. Since the baffle box is wide open on the bottom (enter deteriorated cap), the baffle box is not holding any fuel and gives me the effect of having no baffle box at all!!!

      Now I am really screwed as there is no way of replacing that cap short of cutting the tank open!!!

      Any suggestions now? HELP!!!


    13. 10-21-2007 02:41 PM #13
      fatmobile - Do you have a picture of the bottom of the bafflebox? I'd like to see where the fuel pick-up entry point is located. Does it pull full from within the area covered by the (now deteriorated cap) or outside of the cap?

      Thank you.


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      10-21-2007 10:50 PM #14
      Yeah, I looked at the 2 pictures I posted and thought: I should have taken a picture of the bottom of the box too.
      I'll try to get one posted soon.
      I suppose an inline filter might be in order but I'm not sure this degraded cap would cause your problem with the right hand turns,... unless it happens when you turn left too. The right turn problem is somewhat common,... caused by a rusted out metal line from the box to the output.

    15. 10-22-2007 11:00 AM #15
      Thanks - I look forward to seeing that picture. I am mainly interested in seeing (understanding) where the fuel pick-up draws-in fuel. Is it from within the (deteriorated) cap? This is my current assumption as I don't see how else the filter would be used.

      In regards to an in-line filter, I already have a nice one from Marren Fuel injection. It is a fully rebuildable filter capable of handling the vacuum produced on the suction side of the pump. It is installed between the tank and the pump. I took it apart yesterday and found pieces of the deteriorated bafflebox cap.


    16. Member eatworksleepdie's Avatar
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      10-23-2007 12:02 PM #16
      Mike, it's Tony at SEA. ..

      Fidel says the answer is to forget all this stock gas tank crap and put a fuel cell in the thing and be done with it. It seems to be something that develops over time with the older cars that causes this to happen. It doesn't happen on all of them though. Fidel's NEW 1983 Scirocco does not have the fuel starvation problem at all. Where as his old one did etc.

      There are no replacement tank parts that we know of. So that little rubber/plastic piece that's deteriorated is done for. You'd have to get a whole new tank.
      Alternately, you could try to get an aftermarket gas tank, but who knows how the construction is going to be, or how it's going to perform.

      simply put, get the fuel cell, and enjoy driving it. sorry for the bad news.


    17. 10-23-2007 01:51 PM #17
      How about I buy Fidel's tank and he installs a fuel cell?

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      10-24-2007 01:19 AM #18
      OK I got a picture of the bottom of the box:

    19. 10-24-2007 10:11 AM #19
      Thank you so much for sending this picture. The picks that you have posted have been a big help. You've done the exploratory surgury on the dead tank and enabled me to see how parts function that are not even covered in the Bentley manual.

      Just as I suspected, fuel comes into the surge tank / baffle box, flows through the center filter and then down to the cap on the bottom of the box, where it is then "sucked-up" by the fuel pick-up tube.

      Since the cap on the bottom of my surge tank / baffle box has disintegrated, I effectively have no surge tank / baffle box. My fuel pick-up has just been sucking fuel from beneath the baffle box!

      In short, I'm screwed!

      My next options are to...

      1. Find a good tank
      2. Send my tank out to be rebuilt and include an aftermarket surge tank / baffle box
      3. Install a fuel cell

      Those are all expensive options!


    20. 10-24-2007 12:28 PM #20
      As mentioned in my other thread. A friend just bought a new tank through Auto Zone. $150.00. I had another friend with an 84 GTI that was also having similar issues to you. He put in a new tank and never had another issue. The last thing I would do is cut it up to do a fuel cell. Get a replacement tank and call it done.

    21. 10-24-2007 01:16 PM #21
      It is my understanding that the aftermarket replacement tanks do not have surge tanks / baffle boxes. This makes them worthless for road-racing.

      I called Dorman OE solutions yesterday (Dorman is a provider of aftermarket tanks) to determine if their tanks have internal surge tanks / baffle boxes. The tanks do not.

      Did your friends Autozone tank have a baffle box? My assumption is no. Can you confirm?

      Thanks,
      Mike


    22. 10-24-2007 01:20 PM #22
      I will look into it. Ya may have to suck it up and throw a fuel cell in there or find a good used tank.

    23. Member WackyWabbitRacer's Avatar
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      10-24-2007 03:26 PM #23
      Quote, originally posted by michaeldarr »
      My next options are to...

      1. Find a good tank
      2. Send my tank out to be rebuilt and include an aftermarket surge tank / baffle box
      3. Install a fuel cell

      Options 1 &2 are viable. If your GTI is a street car, the installation of a fuel cell is not a good choice. More details about a fuel cell installation can be provided and why a fuel cell is not a good option for a street car.

      Cheers, WWR.

      WWR
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      Harry Puckett R.I.P. 01-24-2010. You are gone too soon. We had races
      to race, jokes to tell, laughter to share, and cold beers to drink.

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      10-25-2007 12:01 AM #24
      I've never heard of a diesel having the right turn fuel starvation problem.

      A few thoughts:
      If the box was full of fuel it would dump out the bottom of the box and into the pickup, on right hand turns.
      The returning fuel would also dump into the box and flow out the bottom.
      It might work better if the screen wasn't in.

      I don't think that's your problem, or it would happen on left turns too.

      I might have to cut a big enough hole in the top of another tank, pull the box, cover the hole in the bottom, put it back in and put the top back on. A tank rebuild... someday.


    25. 10-25-2007 08:55 AM #25
      Fatmobile - Can I buy the "cap" from your bafflebox?

      By the way, you realize that my car is a fuel injected GTI - not a Diesel. Were you just stating that as a matter of personal knowledge or did you think that we were talking about a Diesel?


      Modified by michaeldarr at 1:57 PM 10-25-2007


    26. Member
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      10-25-2007 11:57 AM #26
      You can't see it in the picture but my cap has a hole in it too,... not as bad as yours but I don't think you want.
      I knew yours was a gasser, I figure it has the rotted out metal line going from the box to the outlet, that's why it only starves on right turns.
      I mentioned diesel tanks not having this problem,... I think it's more difficult for the metal line to rust when it's in diesel fuel,... just a guess. I thought you might be able to find a diesel tank locally, nothing different about it.

    27. 10-25-2007 02:17 PM #27
      Thanks. Diaphrams with holes are nothing but problems.

      Good point about Diesel preserving the tank.

      As an update, I took, wvjodi's advice and have ordered a tank from Autozone. I ordered directly from the store manager and explained that I will want to open the box on site and check for the baffle box. If it is not there, he will give me a full refund.

      If that does not work, I discovered a place in PA that completely rebuilds all tanks. He will fabricate a new surge tank for me in my existing tank and coat the tank with a sealer.


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      10-27-2007 10:48 PM #28
      part number on the diaphram is:
      171 201 740

    29. 10-29-2007 10:08 AM #29
      Thanks for that number. I strongly suspect though that this is not a part available from VW (even though it has a part number).

      I bit the bullet and ordered a gas tank from AutoZone. To my surprise, this tank included a fuel bowl in place of the factory tank baffle box. The Fuel bowl holds about the same volume and has the pick-up and return tubes in the same approximate placement. The fuel bowl has two 3/8" holes in the bottom that let fuel in if below the top of the bowl.

      I set-up a small experiment over the weekend by closing off all tank openings other than the sending unit opening. I placed the AutoZone tank on a pair of sawhorses and filled the tank to various levels with water. I then rocked (tipped) the tank back and forth to try to simulate cornering. The fuel bowl did eventually drain but kept enough volume to keep the pick-up under water for the duration of time that I would be in corner. Granted, I didn't have a pump pulling fuel from the bowl or a return line feeding it but it did appear like it might solve my fuel starvation problem.

      (I then dried the heck out of the tank inside and out and will let it sit for a week before installing)

      I am going to put it all back together this coming weekend and give it a shot. If I still experience fuel starvation, I am going to install a Fuel "Swirl Pot" and auxiliary fuel pump. I did a lot of reading over the weekend about swirl pots and this seems like it could be a good solution. The Brits and Aussies seem to swear by these things.

      I'll keep the post "posted."

      Thanks again for your help,
      Mike


    30. 11-02-2007 09:38 PM #30
      For all folks following this write-up I provide the following:

      I am still in route to a solution. I purchased an aftermarket tank from AutoZone. To my surprise (I'm not an AutoZone fan) the tank turned out to be a pretty good copy of the original. The primary difference was that the surge tank / baffle box was gone. In its place was a simple fuel bowl. The bowl had two 3/8" holes on the bottom to allow fuel to enter should the overall tank fuel level go below the top of the bowl. The fuel pick-up tube entered from the top of the bowl and didn't quite make it to the bottom (a flaw). The fuel return tube dumped into the top much like the factory set-up. The tank is missing one of the vent tubes which means that I would not be able to use the factory closed-loop emissions set-up.

      I was skeptical about the fuel bowl. So, I set up a simple test. I put the tank on two sawhorses and then filled it to varying degrees with clean water. I then moved the middle of the tank to one sawhorse and tipped it back and forth to simulate high-G turns. The fuel bowl did a surprisingly good job of keeping the fuel in the bowl. Now, my test was not a great one because I didn't have a fuel pump drawing liquid out or a return line filling the bowl. It was a pretty static test.

      I came away shocked but still not satisfied. I did further research and discovered that this set-up will probably be good for the street but that there are better fuel bowl designs. In particular there is one that is shaped like a snail shell with a pick-up at the base and a return line into one of the spirals of the shell pattern. This design will work well regardless of the direction the g-forces (braking, accelerating, turning).

      The below graphic shows the general shape that I am talking about. This is not an available part as it is from a European spec 1.4L Ford Fiesta. This is what I am going to ask a fabricator to build for my tank.

      http://www.quantums.info/pictu...8.jpg

      So, I am going to return the AutoZone tank and put that money ($142 with tax) towards having my factory tank cleaned, modified to contain the above described snail shaped fuel bowl as well as two vertical baffles running from the front to the back of the tank. I'd like to solve my problem once and for all and have something that will work for roadracing.


    31. 11-12-2007 09:54 PM #31
      Update: I'm on a double path now. I sent my factory tank to a tank restoration specialist for the fabrication of a new internal surge tank as well as the addition of two vertical baffles. This will be ready later in the winter.

      In the meantime, I installed the AutoZone tank to get me through the winter storage season (crazy I know).

      I'll be selling the AutoZone tank next season. So for those of you following this thread, look for a good deal on a slightly used tank in the early spring (race season starts early in Texas).


    32. 11-12-2007 10:01 PM #32
      I have been following this thread religiously and it is of great help. I was originally going to get a discount gas tanks tank but they are out of business now it seems. What im wondering is how does the autozone tank not meet your standards? Im assuming that it doesn't stall on turns, so what more could you ask for? Pardon my ignorance, im just wondering if its too heavy or if theirs something im not seeing. Please let me know, I need to figure this out.

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      11-12-2007 11:23 PM #33
      Good thread.... I'm 99% positive this is what's wrong with my tank. When I pulled my screen, I think I was looking at the bottom of the tank. My steel tube from the box to the pump is intact.

      I saw traces of rubber inside the box, but I thought they were from the deteriorated line that fills the baffle.... the steel tube that runs along the front of the tank.

      Also, how effective can the screen be if there's a notch cut out, where the feed tube squirts in. Fatmobile's pic shows it at the upper right by the diaphram. This entry point bypasses the screen, altogether.

      Why wouldn't I (or michaeldarr) be able to put a thick, fuel resistant, rubberish (or aluminum) disc in, from the top of the baffle box? The diameter of the disc would be slightly larger than the cyllinderical screen. The screen would sandwich it down, keeping it from moving and would seal the box.

      Or use fuel resistant silicone and glue a disc directly to the bottom edge of the screen, effectively sealing it.

      Fatmobile, which way does that trap door swing.... in or out. And yes; my car starves on right and left turns. Thanks for the helpfull pics.

      -Todd


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      11-13-2007 02:38 AM #34
      That trap door swings inward as fuel flow in, then shuts so it can't get out.
      If the rubber seal on the bottom is toast. It might work better if the screen wasn't in place.
      The fuel trapped in the box would flow out the bottom and into the pickup area easier.

    35. 11-25-2007 10:29 PM #35
      Update: I sent my original tank off to have a nautilus-shaped fuel bowl installed in-place of the original baffle box. While the gas-tank repair shop has the tank open, I am having them install (weld) two vertical fuel baffles to reduce fuel slosh.

      Meanwhile, I needed to get the car on the road again. So, I installed the AutoZone tank. TO MY SURPRISE, THE TANK WORKS!!! Once I had it all buttoned-up, the exhaust up, axle up and brakes bled, I tested the tank. I can not get it to starve! I went to a large, empty parking lot and set-up a make-shift skid pad. I pushed the car hard through continuous left circles (about 10 in a row) and then continuous right circles (again, about 10 in a row). I was lifting the inside rear wheel and really trying to make the tank starve. It did not.

      The only down side to this tank is that I can hear the fuel sloshing left to right. Otherwise, it performs beautifully.

      Once I get my refurbished tank back, I will install it and sell this AutoZone tank for a reduced price. It will definitely solve your fuel starvation problems.


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