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I hope someone can assist with diagnosing my TDI. When I jumped in to head home from work the engine would not start. Once it was towed home we began to try and figure it out and have been stumped.

The starter turns the engine over and it sounds as if has one or two cylinders worth of compression, after that the starter sounds as if there is no longer a load and freely spins at a higher RPM. We have not checked the actual cylinder compression yet. I am hoping it is not bent exhaust valves.

We pulled back the timing belt cover and the belt is still tensioned and not broken or damaged. While turn over the engine the belt appears to rotate just fine. The belt was changed roughly 20k miles ago and it gets regular servicing. Overall mileage is 144k.

We have had trouble in the past with MAS and "limp mode" but otherwise it has been a great runner.

Any help, suggestions, or discussion of similar experience would be appreciated.
 

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Sounds like a few things:

First, it's warm enough that the engine should fire fine without the glow plugs. So forget any glow plug related issues. Your MAS could have exploded and the car will still run so it's not that.

If you can get access to a code scanner scan for codes.

When you turn the key, does the glow plug light on the dash light up? If not, then check relay 109. This prevents any fueling. It's under the dash, behind the panel. The newer part is grey.

A low battery could cause cranking and no start.

The starter not engaging could be a bad starter solenoid or connection to the starter. It should stay engaged for as long as you hold the key. It could also be a bad ignition switch.

The belt could still be tensioned but you have to check for slipping. Turn the engine over to TDC and check the timing belt index marks. If they line up then no broken timing belt.

Check the anti shudder valve - it's the plastic vacuum bulb on the intake manifold. It's spring loaded and should return to the open position if you manually press on the lever. If stuck closed it'll prevent air from getting in.
 

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Was there any clue of problems before this one time? There are pictures of the timing belt tools and the index marks in this thread: http://www.myturbodiesel.com/1000q_how_to/a4/timing_belt_part_1.htm

I believe you don't need the tools to see though, just line it up and you can use a mirror to see. I'm thinking that if the TB slopped around then the marks would be off.

When was the fuel filter has changed? You are supposed to change it every 20k. If the car sits for a long time you could get bad fuel and the black fuzz growing in the fuel tank.
 

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How long does the starter crank the engine then disengage? This sounds it could be a simple fix if the starter is bad. The engine won't fire unless it's turning fast enough. If it engages and then quickly disengages (bad solenoid) then the engine won't fire. Here are some tips on checking the function of the starter: http://myturbodiesel.com/1000q_how_to/multi/starterfix.htm


Yes, see the above link to see where the timing belt index tools fit. Technically, there are no "marks" other than the TDC stamp on the flywheel. The other spot is a slot at the end of the camshaft and the injection pump pin hole.

As mentioned above, check relay 109, battery voltage, fuel filter, fuel pickup in the fuel tank, ignition switch, and anti shudder valve. Here is a pic of that valve.


It should be open. It is NOT an immoibilizer problem since a faulty immobilizer should let the engine should start fine, it just shuts it off after 2 seconds.
 

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It could be so many things, egr flap close, relay109, fuel sensor, fuel starvation, cloggged fuel or air filter, air in fuel lines, fuel pump, Timing not at TDC, low battery, etc etc.
 
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