AHU - Air in Fuel System

kurtzl

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Relay in or out... it doesn’t matter, if the jumper is there. The relay is being bypassed.
I’m curious what’s happening with the engine racing symptom...
-Todd
Thanks for confirming. I cleared codes and tried to start again before I pulled the timing belt and valve covers - no new codes. I could see data from the ESS in the measuring blocks when I tried to start - is that enough conclude that the ESS isn't a problem, or do I still need to pull the sensor and check resistance?

The engine racing symptom is as if I floored the accelerator immediately after starting the car. It's really quick - drops back down to idle almost instantly. This thread http://forums.tdiclub.com/showthread.php?t=138997 describes the issue. In both cases when it's happened to me, I found the rubber o-ring had come off of the solenoid. Put it back on and all is well. FWIW, I also had the limp mode issue that Stealth TDI described.
 

Mozambiquer

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I think I may be simultaneously both very lucky and very unlucky...

I pulled things apart again this afternoon to see how things line up - looks like they don't.

With the flywheel at TDC, I tried to insert the IP locking pin - it won't go in. When I rotate the IP pulley so that the pin goes in place, I can't even see the mark on the flywheel anymore. With the flywheel at TDC however, the cam locking plate slides into place with no issues, just like I'd expect. See pics below.







Correct me if I'm wrong, but I think this means there should be no damage to valves/pistons, but would explain why the car won't start.

So what's the correct procedure for getting things back in place? Obviously I'll be replacing timing belt and tensioner, but is it as simple as locking the cam and crank at TDC, then rotating the IP pulley back until the locking pin goes in?
That sounds like the culprit to me! If the injector pump timing is off, that could cause a no start for sure, now the mystery would be why it's off... But get it all back in time and see what it does.

is it as simple as locking the cam and crank at TDC, then rotating the IP pulley back until the locking pin goes in?
Pretty much that. Then let us know what happens.

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KLXD

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On an AHU the pin is removed before the belt is tensioned and the pump shaft moves so the pin not going in doesn't necessarily mean it's out of time.

How far off is the hole with the crank mark lined up. Is the pump hole CW or CCW from where the pin would go in.

You said you "When I rotate the IP pulley". Do you mean that literally, that you are using a wrench or tool on the pulley? You should be turning the crank bolt. Turning the pump or cam can cause the belt to skip as well as putting a load on the belt and tensioner they are not designed for.

Did you turn the pump pulley and maybe it skipped without you noticing?
 
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KLXD

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I found the rubber o-ring had come off of the solenoid. Put it back on and all is well. FWIW, I also had the limp mode issue that Stealth TDI described.
Has nothing to do with the o-ring in spite of what you've read. There is no room for it to get out of place when installed and the pressure would push it where it belongs anyway.

It was out of place because it stuck to the pump when you removed the solenoid.
 

ToddA1

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I’m not used to seeing belts skip teeth. If you look at the tensioner, is the indicator lined up/near the notch?

If you think this is the issue and since you have everything apart, I’d just rotate the IP pulley, so you can get the pin in. You don’t need to remove the belt. Just give yourself some slack and rotate. I’ve done this many times after a TB job to advance 1 tooth.

-Todd
 

kurtzl

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Has nothing to do with the o-ring in spite of what you've read. There is no room for it to get out of place when installed and the pressure would push it where it belongs anyway.
It was out of place because it stuck to the pump when you removed the solenoid.
Hmmm...what would be responsible for the engine race & limp mode? I agree the o-ring seems implausible as the culprit, but the code indicates N109 and taking it out and replacing the o-ring on the solenoid resolves the issue (at least temporarily). Could it be the plunger is also sticking a bit, and the act of removing/replacing the solenoid and plunger is enough to get it working normally again?
 

kurtzl

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If it has in fact skipped a tooth, this would be the first time I've seen it too (granted my experience is very limited). I do know however, that I've changed the timing belt 3 times myself, and each time the pump pin fit perfectly in the hole when the flywheel was at TDC.

It's pretty hard to see exactly how far off the pin is from slipping into the hole. Best estimate is the pin covers half of the hole it needs to go into, if that makes sense. It's far enough off that I can't see the mark on the flywheel anymore when the pin is in place, so several flywheel teeth off. I can count the flywheel teeth when I get home if that would be useful. The pulley needs to rotate CW in order for the pin to line up with the hole.

I didn't turn the IP pulley directly, but I did turn it via the cam pulley using the counterhold tool. I didn't realize there was enough force involved to potentially cause a problem - it's described as part of the procedure in the A3 timing belt article (http://www.tdiclub.com/articles/A3-TimingBelt/) so I assumed it's a generally accepted method. Thanks for pointing out my mistake!

Could the pump pulley have skipped when I was turning the cam pulley without me noticing? Yes, entirely possible. I have to think it's unlikely though, since it's never skipped prior to this.

I grabbed a picture of the tensioner on my way out the door this morning - looks like all is not well there either.


I like the idea of rotating the IP pulley so that the hole lines up to see if it will start, but I'm concerned that the tensioner appears to have failed. What are the odds that it slips again but this time at the cam?
 

ToddA1

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The tensioner will move as the belt ages/stretches. It’s not designed to keep a predetermined amount of belt tension. It’s normal and I inspect and adjust if needed.

I’d start by getting the cam and crank at tdc, then loosen the belt, line up the IP pulley, then retention the belt. Try to keep the slack towards the front if the car. I usually remove the roller, for a bit more wiggle room. You have nothing to lose.

-Todd
 

KLXD

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Your guess about the plunger hanging up is the only thing I figger was going on IF removing the solenoid actually fixed it and it wasn't coincidental that the symptom stopped. It's more than implausible it's impossible. I've done some measuring as even did up a little picher in AutoCad to show it but I can't find the DVD with all the personal stuff I downloaded from my work computer when I left.

Pulley having to move CW indicates it's retarded from the pinned position. It's also where it would end up if the belt skipped on the sprocket when you turned the cam.

Take a look at the tensioner when you try to rotate the engine using the cam. You will see it retracting due to the load which allows slack between the cam and crank with the pump between. Possibly enough for the belt to skip on the pump.

The Bentley Manual specifies turning the crank if a little critical thinking doesn't convince one.
 

kurtzl

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Sounds like a lot of effort has gone into researching that N109 issue! I wonder if it will ever be completely solved.

I was actually going to look at my Bentley this evening to see what it says about rotating the engine by hand :) I've noticed the play in the belt when rotating the cam pulley but naively assumed that it must not be an issue if the tdiclub article describes that as part of the process.

Not sure if I'll have time to do it this evening but I guess the next step is to advance the IP pulley and see what happens. Here's what I plan to do, please stop me if I'm making another mistake :)

1. Lock cam and crank at TDC
2. Loosen tensioner
3. Remove roller
4. Advance IP pulley until lock pin goes in
5. Replace roller
6. Remove IP lock pin
7. Line up tensioner marks and tighten
8. Make sure pump, cam and crank are still lined up
9. Try to start
 

ToddA1

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That’s pretty much it, but don’t lock the cam. You won’t be able to push the slack forward, if it’s locked.

Use a clamp or softly lock some pliers on the belt and cam gear. You’ll need to rotate the cam by hand keeping the belt tight between the tensioner and crank, pushing the slack forward.

You can mark the belt and IP tooth to give you a visual where started. I don’t loosen too much, only enough to slip the belt off the IP, keeping the belt taut, rotate, and slip it back on. You definitely don’t want to lose the cam to crank index.

It’s less than a 5 min affair, since the VC doesn’t need to come off. If you want to lock the cam, you’ll need to free the gear from the cam.

I think your VC is still off, so do whichever you find easiest. How many miles/years are on the timing components?

-Todd
 

Mozambiquer

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That’s pretty much it, but don’t lock the cam. You won’t be able to push the slack forward, if it’s locked.

Use a clamp or softly lock some pliers on the belt and cam gear. You’ll need to rotate the cam by hand keeping the belt tight between the tensioner and crank, pushing the slack forward.

You can mark the belt and IP tooth to give you a visual where started. I don’t loosen too much, only enough to slip the belt off the IP, keeping the belt taut, rotate, and slip it back on. You definitely don’t want to lose the cam to crank index.

It’s less than a 5 min affair, since the VC doesn’t need to come off. If you want to lock the cam, you’ll need to free the gear from the cam.

I think your VC is still off, so do whichever you find easiest. How many miles/years are on the timing components?

-Todd
You need to loosen the cam bolt and break the cam pulley loose and lock the cam, then you don't need to worry about it taking up your slack.

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ToddA1

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You need to loosen the cam bolt and break the cam pulley loose and lock the cam, then you don't need to worry about it taking up your slack.

It’s less than a 5 min affair, since the VC doesn’t need to come off. If you want to lock the cam, you’ll need to free the gear from the cam.

I think your VC is still off, so do whichever you find easiest.

Yeah, I mentioned that. I just gave options.

-Todd
 

Mozambiquer

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Yeah, I mentioned that. I just gave options.

-Todd
Yeah,I saw that after I commented. I find loosening the cam gear generally the best practice, though I actually didn't do that on my first few.

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kurtzl

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It seems the old cliche is true...timing really is everything.

I didn't get home until late last night, but this morning I advanced the IP pulley using the method Todd described (gently clamping the belt to the cam gear). I only needed to advance by one tooth, and the locking pin slid perfectly into place. Reinstalled the roller, lined up the tensioner and torqued everything. Triple checked the cam, flywheel and IP to make sure everything was still lined up properly. Closed it all up, reprimed the IP...and it started immediately as if there had never been a problem!

So now I'm left wondering how/why the belt skipped. It may be my fault for manually rotating the engine via the cam gear, but I hadn't done that immediately prior to the engine dying. If that's the root of the issue, then perhaps I'd unknowingly caused the belt to run loose, and it just skipped at a random moment.

The timing components have 16K on them and were replaced in August of 2014, so almost 5 years old. About 4 of those years it was just sitting in a garage. I'll still change the timing components for the 5 year rule, but given the fact that the belt skipped, should I avoid running the engine until I do that? I'm paranoid now that I know for sure that was the issue.
 

kurtzl

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HUGE thanks to everyone who weighed in for all the help and advice - if you're ever in the Sacramento area your preferred beverage is on me. Special thanks to ToddA1 and KLXD who have been offering advice for well over a week now, and patiently correcting my mistakes. It's been a frustrating process at times, but equally educational thanks to all the help I received. It's most sincerely appreciated :)
 

KLXD

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I don't recall the chain of events but I'd guess it began with the fuel leak and air in the pump then the timing jumped during your troubleshooting before the pump was fully primed?

My concern with tensioning the belt with the cam sprocket tight is that the belt isn't free to move.

I'd put a little CCW torque on the cam sprocket to take out any slack between the cam and pump and crank and check the tensioner setting to see if it's still where it belongs. if it appears to have loosened up then reset it.
 

Steve Addy

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I don't recall the chain of events but I'd guess it began with the fuel leak and air in the pump then the timing jumped during your troubleshooting before the pump was fully primed?

My concern with tensioning the belt with the cam sprocket tight is that the belt isn't free to move.

I'd put a little CCW torque on the cam sprocket to take out any slack between the cam and pump and crank and check the tensioner setting to see if it's still where it belongs. if it appears to have loosened up then reset it.
I would agree about the cam sprocket not being free but then again you're not moving it all that far and the tension will equalize with one rotation by hand. I doubt that the cam change would be material but if it meant opening the valve cover to check I would probably pass. If the VC was already off then I would check and / or free the cam sprocket.

Having said that I always do the belt tension with the IP pin installed, regardless of what Bentley says. I do it because the IP is already under tension with the crankshaft and there's less of a chance that the IP will pull the crankshaft off TDC if it's held there.

Steve
 

kurtzl

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I'm actually inclined to believe that the air in the fuel system was a red herring the whole time. Certainly a problem that needed to be resolved, but I think the timing jumped the morning that the engine started and immediately died. I didn't rotate the engine by hand until I was setting the pump position to replace the head seal, so as you mentioned earlier, it should have started when I was trying to run off of the bottle. The fact that it didn't suggests that the timing was off from the start of the issue.

I'll pull the cover again and check the tensioner mark with the slack taken up between the pump and cam. When you're checking belt tension after having driven the car for a while, do you free the cam gear before resetting the belt tension? I also wouldn't have thought the change would be significant.

Add me to the list of people who leave the IP pin in when tensioning the belt following a TB replacement, but not for a logical reason like Steve described. Just because that's the way it's described in the how-to :rolleyes:

What's the consensus on driving the car while I order the TB kit? Probably safe, or probably shouldn't trust that tensioner even if the correct tensioning procedure is used?
 

Mozambiquer

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I'm glad you got it going! That would be very frustrating! I had a similar problem with my 2006 jetta, but it was a local shop's fault. It would start, but cranked a long time. Finally I had enough and found that it was one tooth off, but they had adjusted the cam gear enough that it would start. I wasn't happy with them!

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KLXD

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Since the order of events was as you described the you're probably right.

So the obvious question remains is why did it jump? Tensioner loose?
 

kurtzl

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I'm glad you got it going! That would be very frustrating! I had a similar problem with my 2006 jetta, but it was a local shop's fault.
Thanks me too! The good (and bad) thing about doing the work myself is there's only one person to blame. No fun being an a position where the shop screwed it up.
 

kurtzl

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So the obvious question remains is why did it jump? Tensioner loose?
I wish I knew with certainty. When I first started the car after getting back from Australia I tried turning the engine over by hand a couple times to make sure nothing was seized. I did that via the counterhold tool on the cam pulley, but then I drove the car for 8,000 miles without any issues. Did I create a ticking time bomb when I manually rotated the engine? Or did the tensioner just fail on its own?

I'm convinced the tensioner is somehow involved. Correct me if I'm wrong, but if the belt is tensioned properly it seems like it would be impossible for the belt to skip (assuming nothing else has failed/seized, which seems like a reasonable assumption in this case).
 

ToddA1

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Mentioned it before, but belts stretch. Just keep an eye on things.

Will I tell you to drive it, prior to changing the belt? I’ll err on the side of caution and say no.

Am I driving on a belt with 20k and 5.5 years on the components, although I have new parts sitting in the garage.... no comment.

Glad to hear you’re running, without spending much money.

-Todd
 

kurtzl

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Haha well you don't have a confirmed case of belt skipping :)

I've already decided to err on the side of caution, and arranged a ride to the airport tomorrow instead of driving myself. I'll be gone til next week, which will be plenty of time for the new kit to arrive.
 

Abacus

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I grabbed a picture of the tensioner on my way out the door this morning - looks like all is not well there either.
Anyone else concerned that the tensioner is tensioned backwards? The half moon piece should be on the top, not the bottom. Usually they fail when this happens (it cracks and can tear the back right off) and it could be the cause of the belt skipping.
 

KLXD

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Anyone else concerned that the tensioner is tensioned backwards? The half moon piece should be on the top, not the bottom. Usually they fail when this happens (it cracks and can tear the back right off) and it could be the cause of the belt skipping.
Never paid much attention to its orientation after setting it. If it was indeed wound up backwards it might splain things.

How about it Kurt, did you load it CW or CCW?
 

kurtzl

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That's a good eye! I've never paid attention to the orientation either, but always tensioned the same way - CW until the raised mark lines up with the notch.

Had to know what the current state was though, so I just ran out to the garage to grab another pic:



Looks like the half moon is now on top like you describe, so what could have happened with the tensioner to get it upside down? Could that be evidence of tensioner failure, or could that happen as a result of rotating the engine via the cam pulley?
 
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