hard start/no start. air in fuel lines. whereto look next?

[Walley]

I am pulling my hair out and am hoping one of you smart folks can tell me where to look next. I had been having some hard start/no start issues in my 03 Wagon, but only in the cold weather. Here is the whole sequence of repairs and issues in the hopes that one you can help me connect the dots.

-Leaky IP in Sept 2012. I replaced the seals and did hammer mod with my friends Vag-Com to set the quantity at about 3.8 (background info).
-October 2012, CEL and P0128. I replaced the CTS with one from Advance Auto.
-November-December 2012, Intermittent CEL and P0128. Hard starting after cold (30F) nights. Replaced the CTS with one from the dealer and also replaced the thermostat. Checked glow plugs with a multi-meter and removed them to check them using a battery. All were fine. Harness was fine also.
-early January 2013. Still hard starting when cold. Noticed air in fuel line from my filter to the IP. Got a new fuel filter, good o-rings, and a new t-valve from the dealer and replaced all the old stuff. Also replaced the original line clamps with some worm gear clamps.
-Monday. Temperatures below 15F. Hard starting in the cold and hard starting after partial warm-up. Still a lot of and bubbles and air in the fuel line going to the IP.
-Today. Hooked up a bottle with fuel to the IP similar to a diesel purge and ran the car till only a few tiny bubbles remained. I assume this will tell me if the air is getting in on the IP side of my filter. (I don't think this is the problem, but I thought I should check).

If my air leak isn't at the IP, then where should I look next?
Could there be something else that I am missing?

Thanks in advance.

 

[csstevej]

Id still Check the Mickey mouse fitting on the fuel filter, common area for air intrusion. Cover the area with Vaseline and see if air stops.
When you did the IP, did you do it on the car or did you remove it?
Just for peace of mind check your staic and dynamic timing, might be off ( retarded ).

 

[Walley]

I greased up the o-rings before putting in the NEW t-valve, but I guess I could slather more on there and see what happens. Anything between the tank and filter that would cause the car to suck air when cold?

The IP stayed on the car when I replaced the seal for the quantity adjuster, the seal for the cap over the fuel temp sensor, and the large o-ring on the side. No visible leaks now. I am going to go back out and check tonight (still have the bottle hooked up), if no hard start or air bubbles then I assume everything is fine on that end.

I'll need to drive over and see my buddy with VAG-COM to check the timing.

 

[csstevej]

Can't think of anything between filter and tank that would cause air intrusion other than the fuel sending unit.
Out of courisity , how much fuel is in your tank?

 

[Walley]

About a half tank right now.

Just wondering how/why would the sending unit would cause air intrusion when cold? I have heard they have a one way valve that can go bad, or get clogged. But the car will hard start even after a partial warm-up (5-10 minutes of city driving) then sitting for 5 minutes. I was thinking of replacing it a couple of weeks back, but am reluctant.

Update. The car sat in an unheated garage at 15F for 3hours (American hours). Started just fine with the bottle set-up.

 

[csstevej]

I definitely would check the timing. Are you getting a large bubble of air or just streams of small bubbles?

 

[Walley]

Its pretty much a constant stream of lentil-sized bubbles. I'll add that I greased up the t-valve after reconnecting the lines to the filter, then drove around for 15min (five on the highway) and still had a lot of bubbles. I'll check again for a hard start in the morning and call my friend with VAG-COM to check my timing.

 

[terrydtdi]

Are your fuel lines showing some dry rot? Are you running any bio?

 

[Walley]

The "rubber" lines running from the filter back to the firewall (where they connect to the hard plastic lines) look old, but not rotten. I was considering changing these out next.

In the past I ran bio 90% of the time. I usually ran B90 in the summer and anywhere from B10 to B50 in the winter. I moved away from my bio source 2-years ago and have been running on dino-d (with Power Service) about 90% of the time ever since. Hence the reason for the leaky IP seals that I fixed back in September. You just reminded me that I did run a single tank of B80 back in October. I guess there is a chance that it could have picked up a diesel booger and clogged my sending unit, but my vac pressure looks good and the problem is air...not a lack of fuel.

 

[Walley]

I definitely would check the timing. Are you getting a large bubble of air or just streams of small bubbles?

Been thinking about this at work today so I'll respond to my own thread.

Here is a newb question.....if the car starts fine in the cold when I have a Gatorade bottle of fuel connected directly to the IP, then how would my issues be related to timing?

 

[alphaseinor]

how about that piston coming out of the fuel valve on the IP?

 

[lizbiz]

posting

I know this probably isn't the place to do this, but I always have trouble find the button that says post a new thread or post. right now all I can find anywhere is post reply. can anyone tell me how to start to get to a new post when I first log in

 

[Walley]

I know this probably isn't the place to do this, but I always have trouble find the button that says post a new thread or post. right now all I can find anywhere is post reply. can anyone tell me how to start to get to a new post when I first log in

I think you go back to the main page for the "discussion area" where you want to post. Look in the almost upper right corner under the page number and click on the drop down menu for "thread tools". I had a tough time finding it also. probably placed there so newbs like me would read a bunch of posts to find our answer before posting too many redundant questions.

 

[Walley]

how about that piston coming out of the fuel valve on the IP?

Please explain.

Could this happen without first tampering with the IP?

 

[sisyphus]

Timing. Check your timing. My car wouldn't start/hard start in the low 20's. Advanced timing with board member Abacus to 65/100, started the other day at like -8, ran like a champ.

 

[Jolf]

Firstly hello all! I'm new to TDI and loving it

I think I have the same problem, so I don't mean to thread jack, but, can those fuel lines be replaced with just standard fuel lines for diagnostic purposes to eliminate them as a possibility?

 

[Walley]

No worries on the hi-jack. As you umay have seen in my earlier post; I connected a bottle full of fuel between my fuel filter and IP to effectivly take the filter out of the equation (similar to a diesel purge set up) and the car started just fine when cold and after about 3hrs of sitting. It wouldn't do this when connected to the filter previously.

Next I'm going to do the same thing, but with the bottle connected to the hoses near the firewall, which would run through the filter, but eliminate the tank and sending unit from the equation and tell me if the issue is in those lines, or the filter/t-valve which I have already replaced once.

 

[Walley]

Timing. Check your timing. My car wouldn't start/hard start in the low 20's. Advanced timing with board member Abacus to 65/100, started the other day at like -8, ran like a champ.

So I'll ask this question again........if the car starts fine in the cold when I have a Gatorade bottle of fuel and bypass the filter, then how would my issues be related to timing?

No disrespect from this newbie...I just want to learn.

 

[Jolf]

Cool, let me know what happens. I get a nice 2-3" bubble in the clear line every time the car sits for an extended period of time (overnight and after work) . And I live in Phoenix so I doubt temp has anything to do with this equation.

 

[Walley]

OK. I forgot that it is 25F here and I need to warm up the car before the t-valve will function and start sending fuel back toward the tank. I don't have much time to work on this today or this weekend, but will get to it next week.

 

[josh8loop]

I had major issues with air intrusion on mine. I found that the thermo tee and the fuel filter drain on the bottom were huge contributors in my case. Depending on fuel filter brand some of the fuel filter drain plugs have an o ring or a flat seal. Make sure that sealing surface is clean and that the seal itself isn't damaged or cut. I have even replaced my o ring/seal with a new Viton o ring on mine. Also another thing I did that helped on mine is to purchase some Hylomar non setting diesel resistant gasket joining compound available at Grainger.


I slathered it on thermo tee o rings, and put some on the fuel filter connection nipples before I pushed the fuel lines back on. I would be careful putting any on the fuel filter drain seal since if it's lubed with it while it's not tacky to the touch when you tighten the drain down you can displace/extrude the seal and it will leak. Had that happen myself . Like I mentioned, the starts out with moderate viscosity but within a few minutes gets tacky to the touch. It's great stuff to have around and has helped me tons with my air intrusion issues.

 

[josh8loop]

I forgot to mention that I have heard reports of damaged fuel filters that leak air in under slight fuel system vacuum. You could pressure or vacuum test yours to check for leakdown for peace of mind. Use low pressure(10-15 psi) or moderate vacuum(15 inches) for the testing. Also thermo tee o rings are notorious for getting pinched during install. Verify no pinched o rings and that all sealing surfaces of the fuel filter are smooth. Again, use some Hylomar too

 

[Walley]

Update. Car sat in my unheated/detached garage from Friday afternoon till last night (average temp about 25F) with a Gatorade bottle full of fuel acting as my tank connected to the hoses near the firewall on the tank side of the fuel filter. The car started instantly after one cycle of the glow plugs with minimal air in the fuel lines.

Replaced the lines from the firewall to the filter (cause they were old and mushy and I damaged them on the earlier removal) and added worm gear clamps. Drove 15 minutes till complete warm-up. Ate dinner. Went back out to start the car and it cranked for about 10 seconds before starting. Same thing this morning at about 40F. ...guess I need to check the sending unit.

Anyone know if those hard plastic "clips" near the firewall and on the top of a sending unit of an ALH are known to suck air?

 

[josh8loop]

Update. Car sat in my unheated/detached garage from Friday afternoon till last night (average temp about 25F) with a Gatorade bottle full of fuel acting as my tank connected to the hoses near the firewall on the tank side of the fuel filter. The car started instantly after one cycle of the glow plugs with minimal air in the fuel lines.

Replaced the lines from the firewall to the filter (cause they were old and mushy and I damaged them on the earlier removal) and added worm gear clamps. Drove 15 minutes till complete warm-up. Ate dinner. Went back out to start the car and it cranked for about 10 seconds before starting. Same thing this morning at about 40F. ...guess I need to check the sending unit.

Anyone know if those hard plastic "clips" near the firewall and on the top of a sending unit of an ALH are known to suck air?

I suppose those quick disconnect fittings could leak air in. They are usually pretty robust however. I ended up replacing the O rings in my quick disconnect fittings at the firewall, fuel sending unit, and underneath the vehicle in an effort to resolve my air intrusion issue. My issue turned out not to be the quick disconnect fittings. I used some Viton O rings from a kit from Harbor Freight. There are two O rings in each fitting with a brass thin spacer between the two O rings FWIW. Also, on the automatic vehicles with the 11mm injection pump there is an aluminum fuel cooler on the return line to the tank. That fuel cooler has some quick disconnect fittings, and so do the lines that run up from the bottom of the vehicle upwards to the tank. Also, like I mentioned earlier get some Hylomar and apply it where I mentioned.

 

[Walley]

Thanks for the locations of the quick disconnects. I guess I have two pairs since I have a manual. We had a warm up to backyard grilling weather (50F) and the car is running fine for now. When I get back down below 1/4 tank (probably tomorrow so there will be a better chance of seeing and removing any crud in my tank) I will pull the sending unit and do the drill-out mod that everyone talks about. The temps are supposed to drop back down in the mid 20s Thursday and Friday and this will let me know if I have solved anything.

If not, I will try the hylomar, but I don't "think" filter or t-valve are part of the problem. Again, the car started just fine in the cold (25F) when using a bottle of fuel on the fuel tank side of the filter. Right after I put everything back together the cold weather hard starting and air intrusion started again.

 

[josh8loop]

Thanks for the locations of the quick disconnects. I guess I have two pairs since I have a manual. We had a warm up to backyard grilling weather (50F) and the car is running fine for now. When I get back down below 1/4 tank (probably tomorrow so there will be a better chance of seeing and removing any crud in my tank) I will pull the sending unit and do the drill-out mod that everyone talks about. The temps are supposed to drop back down in the mid 20s Thursday and Friday and this will let me know if I have solved anything.
If not, I will try the hylomar, but I don't "think" filter or t-valve are part of the problem. Again, the car started just fine in the cold (25F) when using a bottle of fuel on the fuel tank side of the filter. Right after I put everything back together the cold weather hard starting and air intrusion started again.

Drilling out the tank check valves is worth doing. Also remember just because you hooked up a small container and were able to run the vehicle with the filter and thermo tee hooked up doesn't mean they are yet removed from the equation. The IP has an internal vane based lift pump that sucks fuel from the tank through the filter. The highest suction can be measured at the points nearest to the inlet of the IP. With the inlet tubing and it's approximately 3/8" diameter running back to the tank poses a fairly good restriction to flow and requires more suction from the vane pump and hence higher likelihood of air intrusion. Unhook that inlet tubing and run it from a small container and the vane pump has to pull less suction to get fuel and hence less possibility of air intrusion. The worse possible case for a TDI IP is extremely cold fuel, and long restrictive fuel line runs with points along the fuel inlet plumbing that allow air to come in. Also, for the same reasons mentioned above the fuel injector return lines including the rubber block off cap are suspect. Those lines just love to allow air in once the vehicle is shut off and since the tank is lower elevation fuel tends to reverse direction through the plumbing and seeks to be at the same level as the tank- not good for a TDI fuel system!
What material tubing did you use for your replacement fuel lines? Was it diesel rated? Just curious.

 

[Walley]

Update. 55F last night when I replaced the sending unit. It was cheap and in stock at the dealer, so I opted for a new one instead of drilling the old. The inside of the fuel tank was also much cleaner than I anticipated....just a few flecks of "stuff" on the bottom.
Drove the car around for a while and saw an immediate difference in my vacuum pressure. I will add that it was never abnormally high in the past, but was consistently 4lbs lower after the change. Left the car parked in the driveway overnight and it was 29F and snowing this morning. Car started instantly after one cycle of the glow plugs and I didn't see any air in the fuel lines. The real test will be when try to I leave work this afternoon after 8+ hours in the cold parking lot.

 

[Walley]

Issue solved! Sarted right up after sitting in the parking lot at work yesterday and after sitting in the driveway at 19F all last night. I guess I originally had a bad CTS that wasn't letting the glow plugs cycle long enough, but ultimatly the problem was a clogged sending unit.
Thanks to all who assisted!

 

[whitedog]

Thanks for sticking with us and mostly for posting up the resolution. It always helps others.

 

[ItAintRodKnock]

I still want to know why timing would/could be the issue.(well, not for you now that you're diagnosed)

I live in central Florida, today it was downright cold(I live in Florida incase you missed that)
I think I read 38 when I went to start the car to warmup at 6:30.
Car took "two or three times" as long to crank up. Not thinking about It i did the normal routine, come out get in,clutch in, turn key wait for glow plug light to dissapear and crank, solid cranks just never woke up for afew seconds.
I didn't crank long just longer than usual. Once it woke up it idled fine and I let it warm up for 8-10 minutes and then left for work. She drove fine but after that long of a warmup and then cruising for 7miles at 65 and then hitting city roads no traffic for 5 miles it never warmed up to the usual spot.
Hot days it sits at 190, cooler:cold days usually sits just above the notch next to 190(cooler side)

I don't know if this is something to be concerned about since it is Florida and it won't be cold for much longer. But if it's a timing possibility ill jump on it