Pushing air from the fuel filter?

[Mathius]

So I have a weird problem..
When running my car for about a half hour it starts pushing air threw the lines.
But it's not coming from the pump. Instead it starts getting air from the filter??
I bypassed the filter, and poof!
No more air. But I don't want to run it with no filter..

When running from the filter it takes a gulp of air, and starts recirculating it. Then it's constantly pushing air threw the pump, and huge bubbles come from the filter.
Where's the air coming from?
It's a brand new filter...

[Mathius]

Well....
I came to 3 different conclusions here.
1. The main fuel line is restricted, and isn't filling the filter fast enough?
2. The o-ring on the filter (return line) isn't sealing properly, and is allowing air into the filter?
3. A bit of both coupled with the check valve on the pump allowing fuel in the return line to run back into the pump when I shut the motor off.. Allowing air to get trapped in the system.
That's a long shot. But I'm totally baffled?
It runs just fine out of a pop bottle, or directly from the main line with no filter...

[TylerDurden]

If you have a thermostatic tee fitting on the top of the filter, they are known to leak from stiff o-rings or cracks in the plastic. I usually get the older style filter and bypass the tee back to the tank.

[Mathius]

Yep.
It was cracked under where the pin sits.
Thankfully I had another one sitting here.
I topped off the filter, and burped the lines. Again..
So far so good.
I also deleted the water separator while I was at it. Been meaning to do that anyway.
Took me all of 10 minutes. Then I jammed a bigger/thicker o-ring where that "T" fitting is.

All is well.
I wouldn't have thought to look at that fitting for cracks, so I thank you kind sir..

[TylerDurden]

No problemo, sounds like things are heading the right direction.

If the thermostatic setup is not leaking, you might as well keep it. Down here, it doesn't get so cold, so that fuel filter warming system is not critical.

Alberta is a wee bit further north tho...

[Mathius]

It's not the thermostatic one.
I was a bit vague on what I'm running.
It's an old MK2 Golf, with the N/A 1.6.
That fitting on top of the filter that drains the return back into it was cracked.
Looked like someone had smacked it with a hammer.
I had noticed fuel around the lip on the filter before, but just sluffed it off as some I had spilt while priming it.
It runs mint now!!

[TylerDurden]

If it looks like this, it's actually got a temperature controlled valve inside the tee fitting that feeds the fuel back to the filter until it's warm. After that, it sends the fuel back to the tank.

(Not my pic.)

They started using these in the US around '89... probably earlier in CA.

Glad to hear it's running good!

[Mathius]

Oh..
Well I retort.. lol
I guess it is then. I just thought it was some kind of bypass, or some crap.
Now I know.
Thanx again.

[Fatmobile]

If you list your vehicle in your signature we will know what you are working on when you post.