96 IDI - Fuel draining back to tank?

[toronto_vento]

Hey everyone.  I'm actually an owner of a TDI, you might recognize me from the TDI Club or the Vortex.  Anyhow, this is a question for my gf's brother.

He's got a 96 IDI, and has had an issue with it for the past while.  When the car is running, everything is okay, but when he parks it, say overnight, the fuel seems to drain out of the fuel lines.  He replaced the fuel filter shortly before this began, so I thought maybe that was the culprit.  No, tried a different one with the same results.  Then I started going through some of the TDI troubleshoots (i've spent many hours under the hoods of my old and current tdi).  I got him a new thermostatic tee for the fuel filter, and the o-ring.  Still doesnt help.  I took a look while he cranked, and there isn't any fuel evident anywhere from the injectors, etc (no leaks from what I see).

It doesn't seem like the fuel leaks out of somewhere overnight, it just seems to drain back to the tank.  I'm guessing a seal is gone somewhere, but I'm not sure where to start looking.  Anyone have any ideas on what the problem might be?  I've tried the search function with a few strings, but couldn't really come up with anything.  (no, I'm not a newb to forums, the net or computers)  I know in the TDIs the fuel cutoff solenoid can cause something like this where the O-ring slips off and creates a path for air.  From what I read, though, it seems that if this thing wouldn't work right, he wouldn't be able to run the car at all.  (usually fails closed from what I've read)

What are other areas we can look at?  He's just trying to get the car running reliably again.  There haven't been any other issues with the car to date, so he's a little stressed about this one.  (car's become a headache for him...he doesn't trust it to go anywhere)

If anyone could please chime in, and maybe offer up some places to look.  Both him an I are no fools with tools, but I need a place to start smacking with a hammer.  :lol:

Is it possible that the injection pump is gone or something?  I mean the car runs fine once the fuel gets to the engine, and there is no air in the lines.

Thanks!

John

[jtanguay]

well there must be an air leak in one of the lines, that would explain how the fuel can leak back into the tank.  without an air leak, the fuel cannot flow back into the tank.  It's probably something to do with the fuel filter though...

[commuter boy]

There's a check valve on the lines back at the tank to prevent drainback.

When mine failed last year, instead of trying to replace the hard to get to one back there I just installed the new one in the line on the engine side of the firewall.

[jtanguay]

There's a check valve on the lines back at the tank to prevent drainback.

When mine failed last year, instead of trying to replace the hard to get to one back there I just installed the new one in the line on the engine side of the firewall.

sounds like a great idea...  !!!

[toronto_vento]

Definitely sounds like it could be the issue.  Does the check-valve just fail without warning?

Does anyone have the part number for it?  I'd rather have the part number, than have the dealer troll through the ETKA and maybe order the wrong part.

Does the checkvalve install on the supply line, or on the return line to the tank?  I'm guessing the supply line, as the return line should be controlled via the thermostatic tee.

[toronto_vento]

I got off the phone with the dealer.  Got some part numbers.  Am hoping someone can chime in and let me know that they got it right.  Accoding to the parts dept:

Feed side check valve:
165 201 542

Return side check valve:
3A0 201 542

I know...I only need the feed side one...just posted both in case the dealer got the part numbers wrong.  It's not a cheap part, but if it fixes the problem, it's worth it.  Sure sounds to me like this could be causing the symptoms.

[monst]

For parts you might try http://www.1stvwparts.com...
in any event you can place your part# in there
to see a cost from them........
  I wouldn't necessarily just go and buy that
check valve.... I priced one for 48 bucks....
that is just absurd.... they can charge that
kind of money....... My 91 jetta may have
a similiar setup...  I yanked my check valve
out last night. mine is clogged.....  I couldn't
even blow through it in the direction that the
flow it supposed to be...(restricted).
  I would pop out the check valve and
see if you can blow through it from both sides
(use your mouth- clean it good first). If you can
then it is shot. There is a triangle on it indicating
the direction of flow.
 I am currently running mine without a check valve...
(because it was clogged...). I really would like to see
if I can get a check valve from some where else besides
those thieves....(maybe plumbing supply) 5/16 od check
valve... what is the big deal..... I will try and get one
in plumbing.... I am sure they exist just got to find them.
If I find one I will post.............

[rabbitman]

is the check valve under the car?