LOTS of air bubbles in IP fuel return line (ALH)

[leusgs]

Calling all Injection Pump experts! How does air get in them?

2000 ALH Jetta - starts and idles for 10-15 seconds, then dies. Lots of white smoke.

I believe I've narrowed the issue down to air getting into the injection pump. I've isolated the pump by running clean fuel directly into the inlet of the IP, and running the return line through clear hose into a container. So the factory fuel lines, filter, tank, etc are all out of the picture.

I am able to start the car after I Mityvac the return line to prime the system and remove air bubbles. It will start and idle roughly but will not rev, and dies after 10-15 seconds. Afterward there are lots of bubbles in the return line.


Have a look at this video taken about a minute after I shut the car off:
http://youtu.be/aPXRDVa8qrM


Immediately after shutdown there are even more bubbles in the line - the fuel looks almost white and creamy because there are millions of foamy bubbles!

I'm assuming the return line fuel should not be massively full of bubbles like this.


Could air be getting into the pump from somewhere? What are the possibilities?

[sangretdi]

the 2 small o-rings on the "t" fitting that goes into the top of the fuel filter is a common source for air leaks. replace those o-rings, apply a coating of grease to them for good measure.

ALH cars can have fuel restriction @ the fuel pump. by drilling out the "valve" in the inlet tube, and removing that restriction, will possibly alleviate some air being sucking into the system. this is on my "to do" list as well...

Originally Posted by leusgs

Calling all Injection Pump experts! How does air get in them?

2000 ALH Jetta - starts and idles for 10-15 seconds, then dies. Lots of white smoke.

I believe I've narrowed the issue down to air getting into the injection pump. I've isolated the pump by running clean fuel directly into the inlet of the IP, and running the return line through clear hose into a container. So the factory fuel lines, filter, tank, etc are all out of the picture.

I am able to start the car after I Mityvac the return line to prime the system and remove air bubbles. It will start and idle roughly but will not rev, and dies after 10-15 seconds. Afterward there are lots of bubbles in the return line.


Have a look at this video taken about a minute after I shut the car off:
http://youtu.be/aPXRDVa8qrM


Immediately after shutdown there are even more bubbles in the line - the fuel looks almost white and creamy because there are millions of foamy bubbles!

I'm assuming the return line fuel should not be massively full of bubbles like this.


Could air be getting into the pump from somewhere? What are the possibilities?

[leusgs]

Originally Posted by sangretdi

the 2 small o-rings on the "t" fitting that goes into the top of the fuel filter is a common source for air leaks. replace those o-rings, apply a coating of grease to them for good measure.

You'll notice in my post that I have eliminated the filter for this experiment. I'm running fresh fuel into the IP inlet, and the return goes to another container. Thus the O-rings are not involved. The air is getting in somewhere else.

I also have new 3MM return lines between on all injectors and back from #4 to the IP.

Do I need a new IP?

[sangretdi]

sorry, misread that part of your post. bummer, as those are easy fixes! : )

wouldn't say you need a new IP just yet... could possibly have old/cracked/leaky IP seals that are sucking in air. they have cheap rebuild kits and videos online how to do it. is there evidence of any fuel leaking from the pump?

or any leaks around injectors or hard fuel line connections?

Originally Posted by leusgs

You'll notice in my post that I have eliminated the filter for this experiment. I'm running fresh fuel into the IP inlet, and the return goes to another container. Thus the O-rings are not involved. The air is getting in somewhere else.

I also have new 3MM return lines between on all injectors and back from #4 to the IP.

Do I need a new IP?

[KLXD]

The only seals not under pressure when the pump is running is the shaft seal and inlet pipe but it's hard to believe they could leak enough to kill the engine but still let you prime it with the vacuum.

Lift pump bad and fuel in the pump is boiling? Hard to believe it could fail that badly unless it seized and sheared the key.

[BobnOH]

Was it running good a week ago? a month ago? Is it possible the pump got out of time?

[leusgs]

Check out my other thread describing the history and what I've done so far.
http://forums.tdiclub.com/showthread...ferrerid=96832

I posted this new thread because the fuel bubbles really seem strange to me and I wanted to highlight the fuel bubble issue in the hopes someone who really understands the fuel pump and system would respond.

Basically I bought the car non-running. The previous owner was driving it and said it died. First thing I did was replace the fuel filter which looked old and rusty. After that it started and ran ok for 10 minutes or so but smoked a lot. Then it started to lose power and wouldnt rev above ~1100 RPM.

I've verified timing with flywheel mark, IP hole, and TDC. My VCDS is on the way so maybe that will help.

The IP and areas around the injectors are so greasy and dirty it's hard to tell if it's leaking and where. I need to pressure wash the whole thing but it's 30 below zero here through next week so I can't without making a skating rink on my driveway!

[Ski in NC]

Get an outboard motor squeeze bulb and fuel line and use that to force fuel into IP. Make sure line is clean by flushing, or put a little inline filter in to protect IP. With pressurized fuel, look closely at the IP shaft seal for any sign of leakage. That is under suction when running as posted above. All else on IP is under pressure. If shaft seal is leaking, it will cause your exact symptoms.

I find the OB squeeze bulb is a better way to prime, but that's just my opinion.

Sometimes seals shrink and leak, especially if cold. There's a chance once it runs a bit the seal may start to work. If not, the seal can be replaced without replacing the whole IP.

And how in the world can you work in -20??? That would kill me.

[leusgs]

Originally Posted by Ski in NC

And how in the world can you work in -20??? That would kill me.

It would kill me too.

Is the IP shaft seal behind the pulley? Do I just look in that general area?

[Ski in NC]

Yep, look behind the pulley for wetness, etc when pushing fuel into pump. May be hard to see, but if it is leaking, the fuel will show up somewhere below.

Seeing that heater makes me feel better. Maybe I'm not such a wimp. I changed brakes on an old bug in 5F with wind way back. Ever since then cold really gets to me.

[jimbote]

strange thing about the front shaft seal is it can leak air into the pump but not leak fuel out ... sometimes you can catch one leaking behind the timing cover but most times air gets in but no fuel gets out

[maxmoo]

http://www.youtube.com/watch?v=yRMTEAKsScE
does not apply....
reread first post.....ooops