Air in Fuel Lines (replaced the entire fuel system)

Slowmotion

New member
Joined
Jun 16, 2017
Location
MI
TDI
2005 MK4 TDI Wagon, 2004 MK4 GLI (soon to be TDI), MK4 Jetta Wagon 1.8t, B5 A4 4.2 Avant (swap in progress)
Hey All,

Picked up an 03 TDI wagon 2 years ago as a daily and it worked fine for about a year. Then mechanical issues came along, oil leaks, coolant leaks, boost leaks, etc., and the car sat for about a year as I just didn't have time to fix everything in a timely fashion.

Last year, I finally had time to fix all the issues it had and now I'm having a fueling issue that is making me want to sell the car so I can keep my sanity. Now, before I continue, let me list out what was done to the TDI, engine wise:
-Rocket chips stage 4
-Colt camshaft stage 2
-southbend stage 3 clutch and flywheel
-vnt 17 turbo
-pp520 nozzle injectors
-Id parts downpipe, exhaust
-pp150 euro intake manifold with EGR delete
-11mm pump

When I first started it, it worked fine but, would die at about 3/4 of a tank. When it reached 3/4 of a tank, air bubbles would flood the IP and kill the motor. I tried a new fuel filter and T-valve and that didn't change anything, if anything, it made it slightly worse. I then thought to purge the fuel in the tank and replace it with new diesel. At this point, it started going downhill... Now it wouldn't want to stay running for more than 5 minutes. It would start up afterwards, but would die 3-4 mintues later. It would do this until it wouldn't start at all and the fuel line was one big air bubble. Purging the lines at the injectors would only reset the time running back to ~5 minutes. Next, I tried replacing the intank PD pump, that helped a little but, it didn't change the amount of air in the lines. I replaced the T-valve again just in case the first one was bad and still no change.

just as a note, almost everytime the lines had filled with air, I was only able to start it with starter fuild.

At this point, beyond changing the lines, the only other culprit was the IP. There has never been any fuel leaking from it, either on the timing side or underneath. So, I decided I'd find a used 11mm pump that came from a running car and tired that. Everything timing wise lines up correctly, cam lock tool fit and the fuel pump pin went in (though, I couldn't see or find any tdc marks on the southbend flywheel). The results? It started on the first try and ran beautifully....for about 2 minutes. Then it was worse than before. When I can get it started, it'll only run for about 30 seconds at a really rough idle, like it has a big cam in it, and then stall. I checked the IQ and it isn't perfect but, it is within the acceptable injection range. Also, when it is running, there is quite a bit of air bubbles in the line but, as it's getting closer to stalling, those bubbles turn into super aerated fuel, it looks white there are so many bubbles.

At this point, I'm unsure what is going on that is causing the air bubbles to form. I'm tired of working on it and having nothing actually work and I'm hesitant to spend the time to rebuild either my old or new fuel pump and find that still isnt the issue. So, if anyone has any ideas or suggestions, please let me know. I loved how the car drove before I let it sit but, now its becoming a money pit worse than my B5 S4...

TIA
 

KLXD

Top Post Dawg
Joined
Aug 22, 2009
Location
Lompoc, CA
TDI
'98, '2 Jettas
You have a pressurized supply so assuming the pump in the tank is actually pumping the leak has to be on the inlet side of that pump, no?
 

AndyBees

Top Post Dawg
Joined
May 27, 2003
Location
Southeast Kentucky
TDI
Silver 2003 Jetta TDI, Silver 2000 Jetta TDI (sold), '84 Vanagon with '02 ALH engine
It sit for a year ....

- Could a mouse have chewed a very small hole in the fuel line somewhere .... Oh, you said you replaced the entire fuel system? Or, did you really mean that you replaced the 11mm IP with another used 11mm IP and the unnecessary PD lift pump. Seems if the lift pump is operating properly, the system would be pressurized from the pump to the filter on to the IP as KLXD indicated. If it is in fact pressurized from the Lift Pump to the IP, the Lift Pump must be picking up Air somewhere. The Return Fuel pipe discharges inside the Lift Pump assembly .... must be an air leak before the IP which pushes the excess fuel (and air) back to the tank where it possibly gets recycled making things worse .... just rambling! The IP's suction is likely greater than the the Lift Pump's push ..... just thinking out loud!

I don't think you are telling us everything!
 

fatmobile

Veteran Member
Joined
Jul 16, 2019
Location
north iowa
TDI
an ALH M-TDI in a MK2, a 2000 Jetta, 2003 wagon
Bottle feed it.
If it's a fuel supply problem feed the pump from a container in the engine bay.
Clear lines going to and from the pump?
No air going in and foam coming out?
 

JasonG

Veteran Member
Joined
Nov 20, 2011
Location
Warwick N.Y.
TDI
1994, 2003 JSW (sold), 2012 Jetta
I agree that is has to do with the lift pump.
First confirm that it is running and pumping fuel.
Check the pickup tube/fuel inlet strainer for cracks. The fact this is worse below 3/4 tank seems to point that way.
 

Tdijarhead

Top Post Dawg
Joined
Nov 10, 2013
Location
Lawrenceville PA
TDI
2003 TDI Jetta Daughters Car, 2001 TDI Beetle, Wife’s car, 2005 Golf TDI Mine, all 5 spds
Andybees has a picture of “bottle feeding” or doing the equivalent of an IV of fuel to isolate the tank and fuel lines from the equation. I agree that the air is coming from somewhere, if not the ip then the fuel lines or the added Pd lift pump.
 

AndyBees

Top Post Dawg
Joined
May 27, 2003
Location
Southeast Kentucky
TDI
Silver 2003 Jetta TDI, Silver 2000 Jetta TDI (sold), '84 Vanagon with '02 ALH engine
Thanks TDIjarHead for the reminder .....

I made this very simple set-up to "force feed" the IP and do the diesel purge.

Items needed.
-Jef peanut butter jar (plastic)
-JB Weld
-Filter
-Long slim bolt or something similar
-Plastic 1/4 inch elbow fitting or anything similar that will accommodate your hose(s).

Drill a hole in the center of the red lid and install the long bolt or something similar. This will be the support for the set-up.
Drill a hole in the bottom, then smear some JB Weld around the hole and then push in the Filter Nipple
Drill a hole high on the Jar. There, using a plastic elbow (1/4 inch or size for you hose), smear JB Weld on the Elbow and Hole.. insert allow to cure
Then attach the hoses.

The bottom hose is to feed the IP. The other hose is the return................ You must have the Return!

Pour in clean diesel fuel to about the level of the return Elbow. Screw on the Red lid..... very tight! Air will go in around the center hole!

I have other Photos. If I can find them in this new format, I will post!





 
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Tdijarhead

Top Post Dawg
Joined
Nov 10, 2013
Location
Lawrenceville PA
TDI
2003 TDI Jetta Daughters Car, 2001 TDI Beetle, Wife’s car, 2005 Golf TDI Mine, all 5 spds
I thought about looking for your pics, but I didn’t know if I could link or post them but they are your pics not mine so I didn’t want to presume.
 

AndyBees

Top Post Dawg
Joined
May 27, 2003
Location
Southeast Kentucky
TDI
Silver 2003 Jetta TDI, Silver 2000 Jetta TDI (sold), '84 Vanagon with '02 ALH engine
I thought about looking for your pics, but I didn’t know if I could link or post them but they are your pics not mine so I didn’t want to presume.
With the new TDI Club web site, I have very difficult time with the photos ... Sometime, I may make a list of each pic in each Album .... and file it awar for reference! It took me a while to find those three pics, and unfortunately, there are some better ones!

Edit: I meant to add, the force feed set was made in 2012. The JB Weld, etc., is still in good shape with no leaks..
..
 
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Rrusse11

Veteran Member
Joined
Jan 23, 2014
Location
PA Deutsch Country
TDI
2002 Golf, 5spd; 05 Jeep CRD
The other source of air that no one has mentioned is the fuel cooler, if this car started life as an auto. IIRC it's on the passenger side and is a small finned "box" I think on the return line. Like Andy, thinking out loud,,,,,,,,,,
 

Rrusse11

Veteran Member
Joined
Jan 23, 2014
Location
PA Deutsch Country
TDI
2002 Golf, 5spd; 05 Jeep CRD
KLXD,
Not if it's on the return line, I think the idea is that the pump gets the fuel hot and returns excess to the tank through the cooler. Like I said, just thinking out loud,,,,,,,,, OP has a source of air somewhere in the system.
 

fatmobile

Veteran Member
Joined
Jul 16, 2019
Location
north iowa
TDI
an ALH M-TDI in a MK2, a 2000 Jetta, 2003 wagon
Sometimes air in the fuel is caused by a fuel line restriction.
The vacuum caused will make any dissolved air bubbles grow and become visible.
A vacuum gauge on the fuel input will let you know how hard the pump is pulling.
I didn't mention it earlier because it has a helper pump.
 

KLXD

Top Post Dawg
Joined
Aug 22, 2009
Location
Lompoc, CA
TDI
'98, '2 Jettas
Rr, I don't see a leak in the return cooler causing a lack of fuel to the pump inlet while running. Seems to me such a leak would show as a fuel drip while running and not let air in until shutdown. However low the number, the return is pressurized while running.

I, too, am just discussing. I just don't see anything other than a leak in the supply to the lift pump causing this since it runs ok until he gets to 3/4 tank. Nothing personal.

Fat, that would be a pretty good restriction if it decreased the flow of the lift pump output below that of the IP internal pump but of course it's possible.

Of course, my opinion is based on my understanding of what the OP said and his relating of what's going on.
 

fatmobile

Veteran Member
Joined
Jul 16, 2019
Location
north iowa
TDI
an ALH M-TDI in a MK2, a 2000 Jetta, 2003 wagon
Yeah it would take quite a restriction.
I haven't seen a PD intake pump so not sure how it's setup.
Most pickups have a screen before anything else.
Something with a pump might have a finer screen.
It would be nice to know what the fuel pressure is at the front of the injection pump.

When I have seen a bunch of air caused by a restriction,
it flys back to the tank when shut off.
This was on cars with no check valve.

Old Rabbit diesel:
Once I saw air in the line before the pump,
none before the filter.
I lowered the filter into a jug of diesel while running,
figured when it got to the part that was leaking it would pull in diesel and I'd stop seeing bubbles.
All the way in, still had air coming from the filter but none I could see going in.
The restrictive "OUT" bolt was swapped for a regular banjo bolt and the pump was pulling huge amounts of fuel from the tank.
The vacuum after the filter was expanding the invisible dissolved air.
Last time I told this story it solved the guys problem, ha.
 

AndyBees

Top Post Dawg
Joined
May 27, 2003
Location
Southeast Kentucky
TDI
Silver 2003 Jetta TDI, Silver 2000 Jetta TDI (sold), '84 Vanagon with '02 ALH engine
Fatmobile, that is an interesting story about submerging the fuel filter in jug of fuel.

I've owned and driven VW diesels since January, 1980. I cannot remember one that didn't show bubbles in the clear line right before the IP. However, some were far more "bubbly" that others. Right now, I have an '02 ALH engine in my 84 Vanagon. Until a couple of years ago, I had a regular black hose from the filter over to the IP .. thus, I could not see any bubbles if they were there... No see, no worries! Then, I decided to install a clear pipe and, low and behold, bubbles! So, beginning at the fuel tank, I checked and re-checked all fittings up to and including the filter. My filter set-up is the old MK1 from a VW Rabbit diesel with the screw on filter and banjo fittings. Now, there is only an occasional bubble which is quite small. So, do I still have an air leak or is it vacuum expanding dissolved air?

It has been my intent to install a vacuum gauge on the "in" pipe to the IP for monitoring purposes! ... maybe some day!
 

Marc Bourget

Active member
Joined
Jan 17, 2021
Location
Stockton, CA
TDI
2003 Jetta
2003 Jetta,
I have verified a leak between the tank and before the fuel filter. I want to change the line, (steel recommended in another thread) but note that the fuel lines, after descending below the tank and turning forward, both out and return lines go into a box channel. Looking back from the filter in the engine compartment, the lines are shrouded and it appears there is a triangle cover with two fasteners. First impression I though Torqx. Looking closer, it almost appears to be an allen cap screw, but looking even closer, the "head" of the screw looks "soft" almost like it partially melted from heat. It appears I will have to remove the triangle shaped cover to replace the fuel line. I don't see how I will get a metal line up into the engine compartment without access past the triangle cover, but I don't want to "screw up" the screws or fasteners on the triangle cover.

Does anybody have experience with this issue?

TIA

mjb
 

AndyBees

Top Post Dawg
Joined
May 27, 2003
Location
Southeast Kentucky
TDI
Silver 2003 Jetta TDI, Silver 2000 Jetta TDI (sold), '84 Vanagon with '02 ALH engine
If I were to install a metal line, I would not try to put it inside the channel where the existing pipes are located.

I cannot imagine how a pipe inside the channel could have received a hole. If so, this would be a first brought to this forum.

Have you ruled out that the "hole" is outside the tunnel?
 

Marc Bourget

Active member
Joined
Jan 17, 2021
Location
Stockton, CA
TDI
2003 Jetta
Not sure where the hole is. I did not see a leak on the exposed portions.

What I did observe was it took 15-20 seconds to drop from 10mm Hg to zero after I sealed the end of the line at the tank and used my MityVac at the hose leading to the filter. The MityVac was brand new.

About a month after I purchased the car, the seller had one of those "Oh, by the way, I forgot to tell you that I ran it off the road into a rocky stream bed and holed the oilpan . . ." The bottom of the channel shows some denting, but not enough to pinch the lines.

The line leaks to the point that large air in the line when left over night. If I don't vacuum the line, it won't start. I am reluctant to use starting fluid or crank for 40+ seconds as I've read elsewhere.
 

AndyBees

Top Post Dawg
Joined
May 27, 2003
Location
Southeast Kentucky
TDI
Silver 2003 Jetta TDI, Silver 2000 Jetta TDI (sold), '84 Vanagon with '02 ALH engine
No, I would not use Starting Fluid. 15 second cranking intervals would be fine with about 5 seconds wait in between

I'd be inclined to cut open the spot where damage might be. You may find the spot and be able to repair/splice.

Have you pulled out the "in-tank" assembly for an inspection? Seems there is a filter and/or restriction that is known to be problematic. The Vane Pump inside the Injection Pump pulls very strong. So, if a restriction causes a vacuum affect, when you shut-down the engine fuel is pulled back thru the Injection Pump....... resulting lots of air inside the IP.
 

Marc Bourget

Active member
Joined
Jan 17, 2021
Location
Stockton, CA
TDI
2003 Jetta
This "journey" started with bad fuel. The Truck service that cleaned the fuel tank failed to properly click the top/bottom of the fuel sender together after it was disassembled for cleaning. The float was broken. I replaced the fuel pick-up. I think the old pick-up masked the small leak in the line.

It re- starts w/i 4-5 hours, overnight is too long and I have to pull a vacuum to obtain a reliable start.

I've tried Auto Zone, NAPA (Carquest) and O'Reilly's but no one appears to have the correct diameter plastic fuel line. It's all special order.

Can anyone recommend a plastic line source? I could fish the new line using the old.

Still would like some input on the cover in the engine bay.

I will research how to attach a photo.
 

Marc Bourget

Active member
Joined
Jan 17, 2021
Location
Stockton, CA
TDI
2003 Jetta
The fuel pick up has been replaced.

Appears to be a very small leak as it's good for 4-5 hours. If I wait overnight, I have to re-prime.

Can anyone provide me with a source of replacement plastic line? Auto Zone, Carquest and O'Reilly's don't show an application and all are special order. I could use the old line to "snake" the new line in.

Still need some info on the small, rectangular cover in the engine bay that appears to shroud the fuel lines into the engine bay.

TIA
 

AndyBees

Top Post Dawg
Joined
May 27, 2003
Location
Southeast Kentucky
TDI
Silver 2003 Jetta TDI, Silver 2000 Jetta TDI (sold), '84 Vanagon with '02 ALH engine
I used this hose/pipe for the ALH engine in my 84 Vanagon. I installed it about 4 years ago ...... works fine.

Also, you can heat it, then slide it on fittings ...

Edit: Actually, this is what I used ....... (priced by the meter)


>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>><<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<

 
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Marc Bourget

Active member
Joined
Jan 17, 2021
Location
Stockton, CA
TDI
2003 Jetta
Were you able to "snake" it thru using the original tubing? Or was that not an issue?

You reference two types, did you slip one over the other for additional protection?

Use a heat gun for installation (on low range, I suspect?)

Thanks
 
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