No start on 98 A3 AHU after stalling via clutch mismanagement.

[888]

Okay, long story short as possible.
I have a 98 Jetta with 256k, I haven't owned an AHU for 20 years but this one is 90% rust free so I bought it.
I haven't driven it more than three or four times in the few years I've owned it because of other projects but it never failed to start easily. I sold my 15 Golf so this will become my daily and I decided to have a buddy do some suspension work etc.

I needed to get it out of the barn and onto a rollback so I fired it right up as usual and idled fine without issue, but it stalled when I failed to give it enough fuel to get the wheels out of the little ruts the wheels made in the dirt while sitting.
No biggie, just refire it and go, right?
It won't restart, just cranks. I tried it a few times and no go. My son was there working on getting the alternator off of his 15 Passat TDI so he pops the hood. He hears a slight hissing sound from the fuel filter and sees there is no O ring under the fuel line pressure fitting (under the blue hair pin clip). He also has an ALH Golf, which has an O ring, I believe.

Last thing I did is change the fuel filter some months ago and I figured I overlooked the O ring when I was swapping filters. Then I remembered not getting an O ring with the filter and learning AHU doesn't have one. My son and I tried a few O rings anyway with no change.

I would respond to this post saying the poster didn't get the fuel filter full enough and there is air in the lines. I've put dozens of filters on everything from 1.6 Rabbits to Mk7 2.0 TDI's to 12 valve Cummins trucks without any issues restarting, so is it impossible I screwed this up? No, but it just seems unlikely. The only time I've had to really bleed out a fuel system was after doing a timing belt on an ALH.

So, current state is that it will crank briskly (good battery maintained on a trickle charger), start, and run maybe 5 seconds but stall the FIRST time I try it, but only if it sits for a day or so.
Every additional time I try to start after the first try, it will crank briskly and sputter trying to start but fail to run.
No visible leaks, no hissing from the filter or anywhere else.
Sounds like leak in fuel delivery or air in the lines, right? I agree but why is it better after it sits for a day or more? Shouldn't it be worse as pressure bleeds off?

It's been cold at night but maybe 50 degrees F in the barn when I just tried it, was warmer when this first started a week ago.
Glow plug light comes on for a second and goes off, which I recall being normal on an ALH? Same on AHU?
Just added maybe 2 or 3 gallons of fresh diesel to the tank, it was low enough for the fuel light to be on. It ran fine on whatever fuel was in there prior to me adding some. I used the diesel in that container to change the filter on my Cummins without issues.

Keep in mind it started and ran fine with the new fuel filter before I stalled it via "clutch mismanagement".

I feel like I'm missing something basic, help me out.
Thanks

PS - I would just start cracking the nuts on the injector lines and bleed there but I'm hoping I can find out what's causing the problem first. I'm also thinking I better find a spare set of injector lines first. Those 17mm nuts just aren't coming loose on the injectors.

 

[888]

Or maybe I was initially running off of what was downstream of the filter and it actually stalled because it started getting air via the filter versus the little wheelmarks in the floor?

Still doesn't seem to explain why it starts briefly just once after sitting?

 

[turbodieseldyke]

Yes, the thermostatic tee with the blue clip needs an o-ring. Fill the filter through that hole, reinsert the tee, prime the injectors thru the return line, and hope there's nothing worse like a clogged fuel pickup in the tank.

 

[KLXD]

I thought it had two???

Started once because it had enough residual fuel in the pump to fire. What isn't explained is why it ran for you at all with the new filter.

Wait, Can never remember which is which until changing one but one (AHU or ALH) has the o-rings on the tee, the other in the filter. Possibly the wrong filter?

 

[888]

Yes, the thermostatic tee with the blue clip needs an o-ring. Fill the filter through that hole, reinsert the tee, prime the injectors thru the return line, and hope there's nothing worse like a clogged fuel pickup in the tank.

Filter is a Mann WK842/4 from IDParts shown as correct for an A3/AHU.
There was no O ring with either filter (I bought a replacement to get a new O ring, thinking I had lost the original O ring).
ID Parts web site shows Mann 853/3 for the ALH and mentions including two new O rings for the fuel filter tee.

Seems odd to rely on the tee to seal without help from an O ring. Maybe the tee is just worn out? It's not new by any means.

I've never primed that way, I'll look for details on the web. Thanks!

 

[888]

I thought it had two???

Started once because it had enough residual fuel in the pump to fire. What isn't explained is why it ran for you at all with the new filter.

Wait, Can never remember which is which until changing one but one (AHU or ALH) has the o-rings on the tee, the other in the filter. Possibly the wrong filter?

It started immediately and only ran for maybe 30 seconds max before I let out the clutch and it stalled after starting to move out of the wheel rut. Might have been enough fuel between the filter and the injectors to manage that?

Please see response to turbodieseldyke regarding filter and O rings. My son and I are used to ALH which is why we thought an O ring was missing, too.
IDParts has aftermarket and OEM tees, maybe it is time to get one?

 

[KLXD]

Should definitely be o-rings either on the tee or in the filter.

 

[888]

Makes sense to me as well but no O rings came with either filter. I'll have to do some digging.

 

[Benjamis]

The fuel filter should come with an o-ring installed on it, should be no way for it to fall out of it's groove. The tee fits on top of the knob on the fuel filter that has the o-ring on it, and the tee is held in place by the clip.

I have a brand new VW brand tee that I bought because I thought mine was causing a problem but then inadvertently fixed the problem before I got around to installing it, I'm in SW Ohio east of Cincinnati if you end up needing it.

You could use some tygon tubing too so you can see if there is air in your lines.

 

[888]

The fuel filter should come with an o-ring installed on it, should be no way for it to fall out of it's groove. The tee fits on top of the knob on the fuel filter that has the o-ring on it, and the tee is held in place by the clip.

I have a brand new VW brand tee that I bought because I thought mine was causing a problem but then inadvertently fixed the problem before I got around to installing it, I'm in SW Ohio east of Cincinnati if you end up needing it.

You could use some tygon tubing too so you can see if there is air in your lines.

You're right, thanks for the explanation. The filter has an O ring under the filter port flange, I didn't see it before because I was expecting a loose O ring in the box to fit the tee somehow like an ALH and later cars.
I was struggling with posts that stated one wasn't needed because I thought that meant we would be relying on the dimensions and surface finish of a removeable piece of plastic to create a seal and that didn't make sense. Now I get it....the posts meant no additional O ring was needed.

Okay, now that I have that brain f**t behind me, I still managed to draw in air somehow with a new filter and clip correctly seated. That leaves the tee, which does look pretty beat so I ordered a new OEM tee from IDParts monday that should be here friday.

I appreciate the offer but I'm 6 weeks away from being cleared to drive after shoulder surgery else I'd take you up on that. I'm 20 miles north of Dayton.

I did manage to get the injector nuts loose with a crowfoot and breaker bar so hopefully my son can stop by and see if we can get the air out that way.

thanks for the suggestions and responses.

 

[KLXD]

Yay! Finaly someone to verify where they were on the AHU. Couldn't remember. Don't forget to lube the new tee.

 

[888]

Yay! Finaly someone to verify where they were on the AHU. Couldn't remember. Don't forget to lube the new tee.

dumb question - what do you lube the new tee with? diesel? thanks

 

[KLXD]

That would work. Something with a little more body like vasoline or grease would be better.

 

[888]

Okay, new tee and clip installed, no sign/sound of an air leak there now.

Previously replaced all fabric return lines.

Had my son loosen the injector nuts till all 4 injectors sprayed fuel.

Retightened nuts and refired.

It tried to start after cranking a few seconds and in may run for a second in some cases but died. This happened approx 6 times so I stopped.

Should we be retightening the nuts while spraying fuel/cranking?

Something else?

thanks!

 

[KLXD]

I'm thinking not ignoring you.

 

[888]

I'm thinking not ignoring you.

No worries, join the club.

I've worked with quite a few 1.6 D engines and an ALH and they usually fire up and run rough once I get solid fuel spray at the injectors, gradually leveling out.

I keep a trickle charger on the battery and it's turning over fast enough to start.

It's not like I did an ALH timing belt and the whole circuit was empty. Just whatever air came in around the old tee.

The only difference between reliable starting every time I tried it and current state is changing the fuel filter, which I've done many times on many generations without issue, even my ex-Mk7.

Cause and effect seems simple enough but maybe I'm overlooking something. It's gotten colder here, maybe the glow plugs aren't working. Light comes on and goes off....

 

[888]

One other thing we did....added diesel to the filter to be sure it was full/pulling from the tank. (it was, overflowed immediately).

It's down to 19 F here and there is no heat in the barn so I'm not going to mess with it till it warms up or I get the new kerosene heater going.

In the meantime...I'm wondering if there is a leak somewhere I'm not seeing so I'm going to put down cardboard and paper towels under the car to catch any drips.

Also, I noticed that the fuel filter can slide down in the retaining clamp. Maybe it slid down and put a load on the tee. Long shot, but I'll move it up and tighten that clamp nut.

Only other change (and this might be a big one) is that I added some stabilizer and a few gallons of diesel to a mostly empty tank when I did the filter. This is what I added:

https://m.media-amazon.com/images/I/410GCadvlsL._SL500_.jpg

The stabilizer was fairly old and had been opened but I don't recall it having an expiration date. Regardless, I suspect the ratio of stablizer to diesel may be way too high (one bottle can treat 512 gallons) so I think it would be good to have my son drive me to the local station (I can't drive due to shoulder surgery) and get at least 5 gallons of fresh diesel for the tank.

This could also explain it originally running off of the original undiluted diesel in the lines and now I'm trying to fire off of the new mixture. Long shot, but it's easy to add more diesel to the tank to test the theory.

EDIT - actually, I can probably drain and refill the filter with fresh diesel and see if it starts off of that and dies whenever the tank gets to the engine. Might need two hands for that so might as well wait till my son is available.

 

[KLXD]

Last resort to eliminate problems with fuel and supply system is to rig up a hanging bottle and plumb that to that to the pump. Can even run the return back to the bottle. Many guys have done it to run the car on Diesel purge.

 

[Matt-98AHU]

I've had AHUs jump time when excessive, abrupt force is applied to them, such as too aggressively applying the clutch and stalling it, or shifting way too quickly from 1st into 2nd gear when in a rush.

And I don't mean the belt jumping time (unless the tensioner has been rotated the wrong way). But the crank sprocket bolt on these (the 19 mm 12 point guy) may not be tight enough. The can loosen over time and the sprocket starts to wobble and wear on the crank snout. Anytime excessive force is applied suddenly in such a situation, the sprocket is prone to shifting some on the end of the crank once they've worn.

If you can get a reading of measured value block 004, the actual timing in field 3, while cranking, that might give you a clue on if it has indeed shifted. Although if the injectors themselves are not popping, the ECU does tend to give the injection timing a default value there, which can throw you off.

You can also look at the raw digital decimal data in block 000, field 2.

 

[alanack]

No.
If the crank sprocket was anywhere near loose it would give a lot more warning than a no start.

The AAZ engine had an undersized keyway that would easily fail.

1Z/AHU has a "D" that is much harder to damage than the older engines.

 

[Matt-98AHU]

No.
If the crank sprocket was anywhere near loose it would give a lot more warning than a no start.

The AAZ engine had an undersized keyway that would easily fail.

1Z/AHU has a "D" that is much harder to damage than the older engines.

Not necessarily.

Speaking from experience from the very first TDI I owned starting back in 2004. By 2008 it would intermittently be hard starting and the pump timing would appear as though it "jumped". The outer pulleys wobbled a bit, but it otherwise drove pretty normally once it started.

The body rotted away, I pulled the engine to swap into a clean GLX chassis in 2010, I was shocked when I went to loosen the 19 mm crank bolt. It was barely tight at all. The D shape in the sprocket had worn substantially over time, allowing it to shift on the end of the crankshaft.

 

[alanack]

And you didn't have any other issues??? My crank pulley was wobbling all over the place, belts squealing, and the timing was fine.

The bolt was still "really tight". I replaced the bolt and pulley to be safe but i probably could have just changed that bolt.

Pulley looked fine. I suspect someone replaced the front main seal and didnt replace the bolt and/or follow the tightening procedure.

 

[888]

To be clear on what happened, I'm not talking about a large depression for the wheels to climb out of. This is a dirt floor that was mechanically compacted by the previous owner for his horses to stand/walk on, I have a double layer of heavy plastic sheeting over the dirt as a moisture barrier. I've pushed cars out of similar depressions in the floor with one or two "rocks", it may have just been coincidence that it stalled at a point I thought was related to the wheels. I've never had it not start and take off with no drama so I wasn't paying a lot of attention till it stalled.
Once my son comes over, I'll try starting it again. I loaded the filter with Diesel 911 and mostly filled the tank so we'll see what that does.

 

[alanack]

Noooo!!!! Never ever put 911 in anything!!!!

 

[888]

The body rotted away, I pulled the engine to swap into a clean GLX chassis in 2010....

My son moved midway between Seattle and Vancouver BC a few years back, surprised Mk3's rot so badly out your way. Seems like the climate of the PNW should be better than that, seems to preserve a lot of the older cars.

Yours must have been driven out there from Ohio, haha. I had a 1999 TDI in 2005 with 86k miles and the tower seam already had a hole in it. Rest of the car was perfect.

 

[888]

Noooo!!!! Never ever put 911 in anything!!!!

Why? I thought the purpose of 911 was to remove any moisture and impurities from the fuel system and that's what I suspect has happened via the old stabilizer?

Is Diesel Purge different/better?

Thanks

 

[alanack]

911 is an emergency, last resort for gelled systems.

Its basically alcohol and extremely hard on fuel systems. Absorbing water will also damage fuel systems.



You dont have water in the fuel system, guaranteed.