Flummoxed by Air Leak

[rs899]

I finally got around to changing the fuel filter on my '91 Jetta NA after resurrecting it (PO screwed up timing belt) from the dead.  I decided to use a MkI filter/holder with a clear hose to the IP.  So , I changed it and saw a few constant tiny bubbles followed by an occasional long bubble.

I decided to look upstream for other issues.  I bypassed the undercar water separator and ran a line from what appears to be a check valve directly to the tank outlet.  In changing that (I pulled out the tank strainer/sender assy) I saw that the plastic around the fuel outlet , (a metal sleeve) had cracked, so I JB welded the crack and all around the outlet.  When I started the car I see that the small stream of bubbles has quit, but I still get the occasional big slug of air (lasts about a second at speed).  I don't like this and I am afraid the IP will lose prime somewhere and I will be walking.

Any ideas?

Rick

[Rabbit on Roids]

rig up an electric fuel pump inline. then rig it up on a switch. or just make it run whenever the car is on. i battled air in the fuel of my rabbit for years, then hooked up an el cheapo electric fuel pump up and it has been working ever since.

[rs899]

That's certainly my backup plan, but I hate to add even one layer of complexity if I can avoid it.  If you rely on the electric pump to work without solving the underlying problem, what happens when the pump fails?  You walk home....

In the absence of any other objections, I am going to delete the check valve that sits in front of the already-bypassed water separator and see what happens.  When I suck on the line it seems to take a bit more draw than it should, methinks.

[Rabbit on Roids]

That's certainly my backup plan, but I hate to add even one layer of complexity if I can avoid it.  If you rely on the electric pump to work without solving the underlying problem, what happens when the pump fails?  You walk home....

In the absence of any other objections, I am going to delete the check valve that sits in front of the already-bypassed water separator and see what happens.  When I suck on the line it seems to take a bit more draw than it should, methinks.

you walk home when the electric pump fails? hmm, one time my pump failed, i continued on my way home. im not even sure where it quit working. my guess would be about 10 miles from home, because my car seemed like it lost a little power at that point. swapped in a new electric fuel pump and all was golden. the only thing you have to worry about is chunks of crud in your tank that will clog the electric pump. THAT WILL LEAVE YOU WALKING..

i was left walking more when i didnt have the pump. FWIW...

[fatmobile]

Drive it for awhile, then check again.
 Takes some time to work the air out after a filter swap.

[rs899]

Yeah, it may well turn out to be nothing at all, just the new filter slowly purging itself. At idle, no bubbles at all, but right after I gun it I get a long bubble.  I still think I will delete the check valve for now.  If nothing else, there is still a small piece of old hose between the check valve and the factory line that could be leaking, or there could be some crud in the valve.

Has anyone deleted the check valve and had an issue?

[fatmobile]

I've removed mine with no problem.
I think it's so you can drain the water seperator without letting air into the line.

[rs899]

No more bubbles,  Unfortunately , as this wasn't a controlled experiment, I don't know why they stopped (I don't understand why they were there in the first place, exactly).  Removing the valve may have helped- I broke it in half when I took the (tight) 1/4" line I had on there.  It's possible it had already been cracked.

Also unfortunately, it didn't fix the engine stumbling.  I'm looking at the injectors next (they were newly rebuilt)...