ALH air in fuel lines after sitting overnight

J_dude

Veteran Member
Joined
Jan 9, 2020
Location
SK Canada
TDI
2003 1.9l “Jedi”
Ok so ive been kinda ignoring this issue for a bit... it starts better if it’s plugged in so that’s what I’ve been doing. Anyway I replaced IP head seal (twice, cut it the first time not going in straight) a while back along with the QA seals, and it hasn’t made a difference in starting, although the old head seal was drying up and cracking.
With a clear fuel line on between tank and filter, after shutdown large bubbles slowly accumulate, coming from the filte. After sitting overnight, said clear line is empty, and rough starts occur (although not as severe if it’s been plugged in).
Like jettawreck told me to do a long time ago (yeah, probably should have listened) I am going to take a clear hose straight from the IP suction side to a clean bottle of fuel (not sure how I will make sure it’s clean fuel) and run it for a while then park it overnight and see what she does...
As an aside, would a BEW lift pump solve this issue? Because I want to put one in anyway if I ever find one at a wrecker..
 

burpod

teh stallionz!!1
Joined
Nov 27, 2004
Location
cape cod, ma
TDI
82 rabbit vnt ahu, 98 jetta vnt ahu, 05 parts car, 88 scirocco.. :/
a lift pump is one of the easiest, best bang-for-buck things you can do for these cars. it will ensure you have no air bubbles. you might find some leaks (or not, it's always possible it could be happening in the old sending unit, or maybe some restriction that is causing what may normally not be a leak to suck in air).

a lot of people will ignore a small amount of air bubbles and chalk it up to being normal, but i can assure you, your car will run much better if there are zero bubbles ever. except perhaps if the tank is very low and there are bubbles from the fuel coming back in the tank churning it up.

its fairly easy to make a nice, no-solder harness, add in a fuse to an empty fusebox slot (a micro 10amp will do it) and a relay in the relay panel above your feet. use a ground terminal there and the circuit 30 for power
 

fatmobile

Veteran Member
Joined
Jul 16, 2019
Location
north iowa
TDI
an ALH M-TDI in a MK2, a 2000 Jetta, 2003 wagon
It's common for there to be air on the input side of a filter.
If the filter is clean especially.
If it's a clean filter there isn't much of a pressure drop through the element.
Air doesn't go through a diesel-soaked piece of paper easily.
When the filter is clogged, there is more of a pressure drop and it will suck air through.
 

burpod

teh stallionz!!1
Joined
Nov 27, 2004
Location
cape cod, ma
TDI
82 rabbit vnt ahu, 98 jetta vnt ahu, 05 parts car, 88 scirocco.. :/
it will really only suck air in if there's a weak connection somewhere. the IP creates a LOT of suction. perhaps in a stock car, if there are only a few bubbles (that you can see, you won't be able to see how it is under load at higher rpms however), you may not notice a big difference depending on conditions, although you probably would if you took logs with VCDS. in a non-stock car, if you ever see any bubbles at idle or after car has been sitting, i can almost guarantee you that your car will not be running optimally....
 

jettawreck

Top Post Dawg
Joined
Aug 2, 2004
Location
Northern Minnesota-55744
TDI
2001 Jetta and 2003 Jetta
Do the test from a (I used a gallon milk jug) remote tank, even a five gallon fuel container. It removes all chance of downstream leaks and then you know which end of the system to work on.
I found/confirmed my cracked outlet fitting on my fuel sender this way, even after testing (inaccurately) the sender separately.
 

J_dude

Veteran Member
Joined
Jan 9, 2020
Location
SK Canada
TDI
2003 1.9l “Jedi”
Ok I got some not so desirable news.
I did jettawreck’s test last night, put a clear hose on the feed and return on the IP and jammed them in a clean washer fluid jug half full of diesel, and ran it for maybe 10-15 minutes.
Just started it again this morning, and it started exactly like it always does, sputtered a bunch and then evened out, HOWEVER, there hadn’t been any air in lines...
I guess air in the lines is NOT the issue after all.
So where do I go from here?
 

J_dude

Veteran Member
Joined
Jan 9, 2020
Location
SK Canada
TDI
2003 1.9l “Jedi”
Timing a bit retarded?
Actually I just checked that yesterday, it’s sitting right between the middle and top lines on the graph. Also checked what my temp sensors were reading while cold today, and they were all within a degree of each other.
I may be grasping at straws at this point.
I just now came back in from checking my case pressure relief valve on the pump (literally just read about that trick 10 mins ago) and the roll pin thing was out about an 1/8 of an inch so I tapped it back in.
 

J_dude

Veteran Member
Joined
Jan 9, 2020
Location
SK Canada
TDI
2003 1.9l “Jedi”
Ok well it started MUCH better today after tapping the roll pin back in on the relief valve last night, I sure hope it’s fixed now. It’s still running on the jug of diesel under the hood so I’m going to hook the lines back up to the tank and then we’ll see if it is actually fixed over the next couple days. One good start isn’t enough to make me believe the issue is gone LOL.
 

J_dude

Veteran Member
Joined
Jan 9, 2020
Location
SK Canada
TDI
2003 1.9l “Jedi”
Having a similar issue, what was the verdict? Is it still starting well?
Nope, it started well once and then it went back to rough starts again lol.
And I just checked the case pressure relief again last week and it was still holding in place so it isn’t because of that.
I’m thinking it’s a combination of things including possibly slow cranking speed due in part to a battery drain I’ve been having, and partly my starter.
It seems if I let off the starter as soon as possible after it catches then it fires up better than if I hold the starter on for a few seconds... I don’t know, it’s driving me mental I think haha
 

thahn8991

Member
Joined
Jun 5, 2022
Location
MN
TDI
ALH
Pulled mine tonight and found the roll pin was almost pushed out. Tapped it back in place. I'll test it out and report back.
 
Last edited:
Joined
Sep 4, 2022
Location
Nevada
TDI
2003 Jetta Wagon TDi 1998 Jetta Tdi
I solved my issue! I went back to a stock style setup with Mahle fuel filter and FEBI tee. I realized that two thing were happening.

One: Removing the return line tee/check valve at the filter was allowing fuel to drain back to the tank. This would cause poor starting.

Two: The WIX filter head has the fuel outlet on the side of the body and has a pocket up in the top that can gather air. Any air that may enter the fuel stream will build up in the pocket and cause larger bubbles to occur. Example: if you hit a bump or go up a hill etc, the bubbles are released. Or even after a while at idle, if you shake the filter, bubbles would come out. A filter head with an outlet at the top of the housing would eliminate this. Then, if you add a check valve in the return line, it should solve the issue. Or just go back to the stock setup with good quality parts and it will solve your problem. Stock filter has fuel outlet at the top.

Hope this helps. I was ripping my hair out.
 

J_dude

Veteran Member
Joined
Jan 9, 2020
Location
SK Canada
TDI
2003 1.9l “Jedi”
OK I'm back with this one again. I haven't been using the car much it sat for most of last year and I did some other work to it, then I drove it for awhile last fall until I got my truck going which I drove up until now and now I'm messing with the car again and seems to be getting worse.
Took it out to my brothers place last week or so which is about 300kms one way, and on starting it for my return trip it wasn't plugged in and had been sitting for a couple of days so I pumped the primer bulb I had installed a couple of times and it still started kinda hard. Also started sort of misfiring/stumbling and smoking between 1400 and 2000 rpm, but only briefly, and then it clears up after a few seconds if I rev it up past 2k.
This stumbling is something new, that it didn't do previously. Then later that day I stopped at a friend's house for a couple hours and the car nearly didn't start afterwards... 😳
So since then I haven't really driven it, but just yesterday I got my BEW lift pump installed, thinking it might help somewhat but it doesn't seem to make a difference, even after sitting for an hour it will sputter for a second once it starts.
Now, I don't understand this, because when it was starting so hard at my brothers place and then later at my friends house, after I pumped the primer bulb it started better, (To be specific, it cranked over but didn't fire, so I primed it and then it fired up, could also hear fuel trickling into the filter while priming.) so it seems like the issue IS that it was losing prime, however, if that is the case then I would expect it to improve with the addition of the lift pump, which it has not...
Other random notes:
- If I keep it plugged in it starts much better, but still sputters a little and does the stumble thing off-idle.
- My lift pump is working, I hooked up a gauge and it was pushing around 10-15psi (my 160psi gauge isn't super accurate down low) and the check valve in the sending unit is also working, it held that pressure after I shut the key off.
- I also have a new case pressure relief valve in the IP.
- I have reverted back to the stock fuel filter with new thermo T.
- There are no visible fuel leaks anywhere, which should have presented themselves with the addition of the lift pump.

So, where do I go from here? Is my injection pump shot?
I wonder this because I know cavitation is BAD in high pressure things like this, and I've started this car many times while this issue was present, so theres presumably been a lot of air in the fuel, doing what it does under pressure...
I'm getting very frustrated with this 😝
 

P2B

Top Post Dawg
Joined
Jan 11, 2006
Location
Toronto & Muskoka, Canada
TDI
2002 Jetta, 2003 Jetta, 2003 Jetta Wagon
Gravity feed the pump directly from a bottle hung from the hood. If it still misbehaves you have isolated it to the pump. It is possible for a bad seal to allow air in but not leak fuel out.

The stumbling and sputtering sounds like a pump issue, surprised it's not throwing a code.
 

J_dude

Veteran Member
Joined
Jan 9, 2020
Location
SK Canada
TDI
2003 1.9l “Jedi”
Gravity feed the pump directly from a bottle hung from the hood
Well I guess I'm chasing my tail, just read through this thread again and in post 36 I sort of did that already.
I say sort of because I didn't hang it from the hood, I had the jug sitting in front of the IP. Probably wouldn't make a difference but I will rig it up again tomorrow and this time get it higher so it will gravity feed with clear lines, and then we can be absolutely certain there are no air bubbles. It gives me something to do anyway.
 

P2B

Top Post Dawg
Joined
Jan 11, 2006
Location
Toronto & Muskoka, Canada
TDI
2002 Jetta, 2003 Jetta, 2003 Jetta Wagon
Get it running smoothly from the bottle, shut it down, leave it overnight. If it starts hard in the morning, pump is letting air in.
 

J_dude

Veteran Member
Joined
Jan 9, 2020
Location
SK Canada
TDI
2003 1.9l “Jedi”
Get it running smoothly from the bottle, shut it down, leave it overnight. If it starts hard in the morning, pump is letting air in.
Ok I did this, with clear lines, and there were no bubbles in either line, and it still started roughly and did the sputtering/smoking thing. Must be the pump, right? So I grabbed a known working pump from a recently acquired parts car and swapped it in and guess what?
Still does the sputtering and smoking! Can't say whether it starts any better yet as I only just got the pump bled and started today but my hopes aren't particularly high... I'll check that out tomorrow.
😫
So where does that leave me? Is it a wiring issue? That's the only thing that comes to mind really but I can't see how that would cause it.
 

J_dude

Veteran Member
Joined
Jan 9, 2020
Location
SK Canada
TDI
2003 1.9l “Jedi”
Or could it be injectors? Weird that it would only happen between 1400-2000 though.
 

CanadianALH

Veteran Member
Joined
Aug 21, 2023
Location
Canada
TDI
2002 Jetta 5spd 2006 Jetta DSG (wifes)
Wait... isn't that about when the second stage pops?
Are the injectors in there known to be balanced and pop tested. Or did the PO buy some off kerma and slap them in one Saturday
 

J_dude

Veteran Member
Joined
Jan 9, 2020
Location
SK Canada
TDI
2003 1.9l “Jedi”
Are the injectors in there known to be balanced and pop tested. Or did the PO buy some off kerma and slap them in one Saturday
I'm not sure, unfortunately I'd guess most likely the latter, and that thought has bugged me for a while. But I'm not sure if that would have any affect on this? The issue seems have gradually been getting worse.
I suppose maybe that could be the issue, it would give me a real reason to get those .260's anyway... 😂
 

burpod

teh stallionz!!1
Joined
Nov 27, 2004
Location
cape cod, ma
TDI
82 rabbit vnt ahu, 98 jetta vnt ahu, 05 parts car, 88 scirocco.. :/
Take an 001-004 log i guess? Did you set pump timing down where I suggest? Halfway from red to blue?

Also could take 004 only log, just note try coolant temp
 
Top