2 Wheel Drive Gas Tank Cut Open

djkeev · Last edited by djkeev on Sun Jun 21, 2015 6:45 am; edited 1 time in total

I just thought some might like to see the "mysteries" of the Vanagon Fuel tank.

Image may have been reduced in size. Click image to view fullscreen.

Dave
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tpinthepack · Posted: Sat Jun 20, 2015 1:17 pm Post subject:

Does not look as bad as I would expect. Do you feel the same or no? Thanks for sharing.
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1968 Manx N.O.S. w/ Barrett Chassis
1960 Single Cab 1914 w/ 40 DLRA's
1990 Vanagon DOKA
1972 Super Beetle
1979 Super Beetle Convertible
2011 Porsche Cayenne

Merian · Posted: Sat Jun 20, 2015 1:37 pm Post subject:

shows why coating is a bad idea

- what is the function of the slot?

djkeev · Posted: Sat Jun 20, 2015 1:51 pm Post subject:

If you look at the bottom of your tank you will see a protruding circle in the center.

That circle is where the fuel is both sucked out of the tank and returned to the tank.
When your fuel level is low. It no longer floods the intake screen. It still gets sucked in the edges of the screen but also seeps under the plate into the intake well.

I cut away the cover of this circle inside the tank, where the two plastic filter screens are fastened.

The cover is spot welded in four spots, in between the spot welds are the slots that let fuel drain into the pump pickup area.

Bottom of my new Tank.....

Inside of my new tank. Much simpler, notice that there are no filter screens.

The pick up and return hoses still feed into the circular well but just enter through slots cut into the square sheet metal cover plate.
The new Slots are much bigger and easy to see. The bigger openings are needed due to the lack of the plastic intake filter screens.

There are still baffles to reduce sloshing.

Is it better? Probably not but certainly cheaper to build!

Dave
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Merian · Posted: Sat Jun 20, 2015 2:38 pm Post subject:

if I follow you correctly the OE tank allows unfiltered fuel to flow out - esp. when the level is low

is that right???

why would someone design it that way?

djkeev · Posted: Sat Jun 20, 2015 3:04 pm Post subject:

It Isn't a huge slot, only the blade of the putty knife fit. It seems to be an "Oh Well, if some unfiltered fuel gets through the slot..... No big deal" situation.

Most of the fuel will have obviously passed through the screen..... And did by the residue evidence on the intake screen.

Dave
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Wildthings · Samba Member Joined: March 13, 2005 Posts: 52371

The question is how to do on the road repairs when the fuel pump starts to cavitate in the middle of nowhere.

djkeev · Posted: Sat Jun 20, 2015 4:31 pm Post subject:

VanShrugs · Posted: Sat Jun 20, 2015 6:57 pm Post subject:

Thanks Dave, for the fine photos of an OEM 2wd fuel tank.

Gotta love Vw engineering and attention to detail.
The outgoing and return fuel from/into the tank is filtered.
The gaps left for a very empty tank.. understandable, at least to this dolt. Smile

Last time I checked with a Vw Dealer in Canada ~ 2004.
An OEM tank (like in the photos) retailed for around $650 Canadian-$. As many on Samba will know, the aftermarket tanks do not contain/have the 2-filter baskets. Cannot fault the aftermarket though. For the cost of a replacement tank today.

Save your original tank if possible!
If rusted internally? So sad. Few treatments, that I'm aware of, will treat the rust without harming the 2 filter baskets.

An acid etch with phosphate follow-up might slow the rust but, what will these two chemicals do to the filter-basket plastics?

VanShrugs

tjet · Posted: Sat Jun 20, 2015 7:14 pm Post subject:

IMO, you really don't want a filter in the gas tank.

It looks like you could swap the feed line with the return line if for some reason you had a no-flow situation

djkeev · Posted: Sat Jun 20, 2015 7:23 pm Post subject:

Forthwithtx · Posted: Sat Jun 20, 2015 7:24 pm Post subject:

The "brand new" (but 12 years old) replacement tank that came with my van was more like the OEM than the replacement you peered into. It also had a little more space between the circular depression and the sheetmetal cover.

This was especially exasperating for me, because whoever shipped the tank to the PO added pink foam peanuts to the box, which entered the tank through the grommet openings. I spent over an hour trying to retrieve them using a vacuum, gravity, coat hanger wire, anything I could think of. At least one peanut made it into the space between the depression and the cover, and so I had to assume that gas was either going to dissolve it quickly, or not at all ( I suppose I could have tested that).

Also, a couple small pieces of plastic came out. Maybe the tank was mishandled, I have no idea.

No matter. That tank lasted only a few miles before the charcoal canister hose that I purposefully plugged (to keep out junk during my Subaru swap), caused the tank to implode. Very Happy

tjet · Posted: Sat Jun 20, 2015 7:37 pm Post subject:

djkeev · Posted: Sat Jun 20, 2015 7:57 pm Post subject:

djkeev · Posted: Sat Jun 20, 2015 8:01 pm Post subject:

VanShrugs · Posted: Sat Jun 20, 2015 9:50 pm Post subject:

Dave,

Given your observations, I do agree.
The usual, do not assume! As I did here.

An OEM tank with fixed filter baskets [meaning non-replicable]
have a limited life.

Better to have a (replaceable) filter-sock over a fuel [in-tank] pump or filter before and/or after the main fuel pump.
The point here is replaceable when requirred.

VS

Snort · Posted: Sun Jun 21, 2015 5:22 am Post subject:

I appreciate what you're doing here but I don't buy the visual light test you are doing on that filter unless you are using that light show to demonstrate a flow problem that you confirmed by some other test with fuel not able to flow through that lower screen section. By your reasoning the fuel would only flow through the top part of the orange screen and when the fuel level got below the top it stopped flowing. Was this actually happening to you?

Remember those baby bottle nipple commercials? They often used animations to try to convince you that there was a problem with old fashioned nipples so that you would rush out and buy their nipple for twice as much money, using that baby screaming as a guilt factor, you bad bad parent. Your light test seems more like that baby cartoon trying to demonstrate a problem where possibly none exists.

djkeev · Posted: Sun Jun 21, 2015 5:43 am Post subject:

djkeev · Posted: Sun Jun 21, 2015 7:34 am Post subject:

Well.......

I got to wondering, how pourous is that filter screen?

I cannot scientifically measure the volume that passes through but I can by simple observation SEE what passes through.

I cut out one of the filter screens and using duct tape strengthened the edges and formed it into a slight bowl shape.
I know that the adhesive on the tape has a very short half life in gasoline so this is a one shot deal.

I wondered if the screen has a residue from sitting that gas will cut away?

Anyway, I placed my bowl over a small shot glass and then using a straw and finger over the open end siphon transferred some fuel (Shell E85, oxygenated, unleaded regular) to the filter bowl.

What did it do?

It filled the bowl and then slowly.... Ever so painfully slowly seeped through the screen, not unlike water seeps through coffee grounds to make coffee.

Rube Goldberg flow test results?

Fail!
Even if one were to suck fuel through this membrane, it would be hard going.

Dave
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Beetle
https://www.thesamba.com/vw/forum/viewtopic.php?t=482968&highlight=74+super+vert

alaskadan · Posted: Sun Jun 21, 2015 7:58 am Post subject:

Maybe you could also repeat that rube-ish test with the portion of screen from the top of the pickup too. Though its pretty obvious that screen was loaded up with tank sealer.


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