Need help diagnosing: starter too weak to turn engine, but battery tests good

[misterpepper]

My '09 2.0T won't start. I'm wondering if any of you can help me diagnose or troubleshoot the problem. The symptoms are these:

When I push the start button I can hear the starter engage, and basically not have enough strength to turn the engine over. It has seemed weaker to start for a few weeks, like the battery was low, but has always started.

The first few times that it didn't start I heard what sounded like the click of the starter, and then the starter motor spinning without engaging the flywheel, until I shut off the ignition. Now it sounds like the starter engages the flywheel but can't turn the engine, similar to a traditional weak battery but without the click-click-click of the solenoid as power drops.

I replaced the (original) battery about 6 months ago because it didn't have enough oomph to crank the engine, and that fixed the problem until now. The alternator has always seemed weak and only charges to maybe 13V, so I've long suspected it of going out soon.

When the problem started I measured the resting voltage at 12V (9.5V under load) so I took the battery out and charged it. No difference, except now the voltages are 13.0V resting and ~8V under load. I had the battery tested and it tested good (which I would expect being only 6mos old).

Reading online I have not seen many starter motor failures. I have also seen a few wiring harness failures. Thinking the wiring harness was the problem, especially since the alternator shares the same harness, I tried jumpering between the positive lug under the hood and the positive on the alternator to give the current another path to the starter. No difference. I was hoping to determine if there was a break or weak point in the harness between the battery and starter. I will try jumpering between the battery and the positive lug under the hood, and from the underhood lug to the starter to see if that makes any difference, but I'm not hopeful.

Reading online I'm getting more worried that the dreaded timing chain tensioner might have gone bad and that some plastic bits, or mis-timed engine valves, are what is preventing the engine from rotating. What is the preferred way to check for this without causing additional damage assuming the tensioner has failed?

How likely is it that it is just the starter and what can I do to test it while it is still on the car? Has anybody changed theirs? I'm concerned about removing the engine mount bracket that straddles it. I'm guessing I need to remove either the airbox or the fender liner to get to at least one of the bolts. Any help here is appreciated. Thanks.

[misterpepper]

Also, jump starting the car didn't help. I've checked the ground at the battery, and the 2 grounds near the starter and all are good. I have not yet pulled codes, either by Carista or Vag-Com, but will hopefully be able to tomorrow. If I were to manually try to turn the engine over, or even just bump it a little to free up anything that might be stuck, which direction should I turn it?

[misterpepper]

So the update is that relieving some pressure on things by turning the crank backwards a little bit caused a noise coming from the timing chain area. Not good. An inspection showed that I have an older style timing chain tensioner still, but it didn't appear to have failed in the typical lose the clip type way, if at all. My car has had the 2.0 oil consumption updates, so I was hoping that may have been changed. I tried to get the top cover off to see if I could see whether the timing was still correct for the top sprockets, but I could tell that getting it off with the bumper still in place was going to be next to impossible, so I went ahead and tried to start it again, hoping that the noise I heard was possible the starter getting unstuck from however it was jammed. Unfortunately whatever was jamming things seems to have re-jammed itself. Hopefully no major damage has happened to the head or valves, unfortunately now I think my next step is to get it to my garage where I can pull the bumper and check/replace the timing chain tensioner bits, take the starter off and test it, test the wiring harness and possibly replace it and do a leakdown test to see if I managed to bend valves or not. Not a happy day.

[misterpepper]

Well, after getting most of the way into replacing the tensioner I stuck a borescope down the cylinders and it looks like I've dropped a valve. Now I'm trying to weigh my options between trying to swap in a new head myself, having a shop do it, or looking for a used low mileage engine. Next step is probably pull the existing head to see if the cylinders and pistons still look good enough to warrant keeping.

[Crucible35]

My '09 2.0T won't start. I'm wondering if any of you can help me diagnose or troubleshoot the problem. The symptoms are these:

When I push the start button I can hear the starter engage, and basically not have enough strength to turn the engine over. It has seemed weaker to start for a few weeks, like the battery was low, but has always started.

The first few times that it didn't start I heard what sounded like the click of the starter, and then the starter motor spinning without engaging the flywheel, until I shut off the ignition. Now it sounds like the starter engages the flywheel but can't turn the engine, similar to a traditional weak battery but without the click-click-click of the solenoid as power drops.

I replaced the (original) battery about 6 months ago because it didn't have enough oomph to crank the engine, and that fixed the problem until now. The alternator has always seemed weak and only charges to maybe 13V, so I've long suspected it of going out soon.

When the problem started I measured the resting voltage at 12V (9.5V under load) so I took the battery out and charged it. No difference, except now the voltages are 13.0V resting and ~8V under load. I had the battery tested and it tested good (which I would expect being only 6mos old).

Reading online I have not seen many starter motor failures. I have also seen a few wiring harness failures. Thinking the wiring harness was the problem, especially since the alternator shares the same harness, I tried jumpering between the positive lug under the hood and the positive on the alternator to give the current another path to the starter. No difference. I was hoping to determine if there was a break or weak point in the harness between the battery and starter. I will try jumpering between the battery and the positive lug under the hood, and from the underhood lug to the starter to see if that makes any difference, but I'm not hopeful.

Reading online I'm getting more worried that the dreaded timing chain tensioner might have gone bad and that some plastic bits, or mis-timed engine valves, are what is preventing the engine from rotating. What is the preferred way to check for this without causing additional damage assuming the tensioner has failed?

How likely is it that it is just the starter and what can I do to test it while it is still on the car? Has anybody changed theirs? I'm concerned about removing the engine mount bracket that straddles it. I'm guessing I need to remove either the airbox or the fender liner to get to at least one of the bolts. Any help here is appreciated. Thanks.

That battery is toast dude. If you are dropping voltage that much under load....not to mention that 8V on a 12V battery is considered over-discharged....you'll need to replace it. The "resting" voltage of 13v may seem good to a meter, but it really doesn't matter if it's dropping 5V under load on these cars. 1-2V maybe but not 5.