[Vwdiesel] Bubbles in the fuel line

[Sandy Cameron]

At 12:18 PM 9/13/03 -0400, you wrote:
>Thanks to all who responded to my fuel filter question.
>
>I am getting bubbles in the fuel line. I have always heard that this is
>a result of a leak in the line somewhere. Is it normal for the return
>line to have bubbles?
>
>Where is the most likely spot for the leak to be? I can see most of the
>line except where it goes through the sub frame under the passenger
>seat.
>
>Is it possible that a restriction in the line could cause bubbles from
>the pump trying to pull a vacuum?

Yes. if your lines are pinched or blocked, or the dread check valve is stuck
(after using veggie), the pump will pull hard enough to draw air in past the
shaft seal, but you will not see this in the suck line, just the return.
>
>Will I cause any damage blowing compressed air through the line from the
>fuel filter back to the tank?

The check valve would try to prevent this until it explodes.

There are several connections at the water separator. the suck line comes
from the tank unit (reached under a round plate on the floor of the trunk),
then in to the top of the water separator, then a line (rubber hose) exits
the top of the water separator and comes down close to the front of the
wheel arch, where the check valve is spliced in, and another short length of
rubber hose goes from the check valve  on to the blue plastic supply line
that goes to the engine room. Jack and remove the right rear wheel to reveal
all this stuff.

The check valve can leak air into the line, and will be wet with fuel if it
is leaky.
Also, on old cars with salt exposure in the north, the steel crimp sleeve
used to clamp the rubber hoses to the plastic lines, etc, will crumble away,
and have to be replaced by tiny gear clamps.
My experience with these is that any time the lines are disturbed around the
separator, you should drop it and remake all connections in the area with
new hose and gear clamps, (fortunately, stainless steel)

>
>Under the tank on the passenger side is what looks like a box with a
>round thingy that can be turned. It looks like the fuel lines run in
>this. What is under there?

That's the water separator. The knob opens the drain valve permitting any
trapped water to drain out. DSrain a little every year to be sure. Be
carefull the knob does not crack off in your hand. it siezes up without
periodical use. Have a large drain pan handy in case you break it off. The
tank will empty (slowly) until it is completely empty.

Sandy