1.8T no start

[5ktq]

I went for lunch today, stopped to grab some food.. got back in the car and no start. Tried 3-4 times, waited a couple minutes and then it started.

Fuel pump primed each time, so I doubt it's a pump / relay issue there. Fuel tank is almost full so I'd imagine it's not related to the over-the-hump mini pump thing.


Ignition system looks ok, I changed to NGK iridium plugs the other day.. ..6...IX ones BK6RE-IX?. Coilpacks are the current ones, guess PO probably had them recalled.

So I'm thinking it's a sensor on the way out, especially with it only doing it when it was warm. On my old 5000 the crank sensor was pretty flaky and would do this, it looks like that's a common cause on these too.
What other sensors will cause a no start, though?

What about the sensor on the camshaft, or the MAF. Will it run poorly when those have failed, or not start at all? Seems to me as long as you've got crank sensor it would at least limp, but.. that's why I'm asking I guess.


I didn't notice if the CEL was lit before I cranked. I guess if that's out it might be the relay for the ECU et al, which I'm not sure where it is. Some say by the drivers knee, others say under the ecu in the cowl box thing. I did have an ECU relay die on a TDI once.

Guess I'll try and pull codes and see if there is anything useful. If it was immo-related it would start, run a few secs, then die, right? and have an immo light in the dash..?

[leightonw]

I would check crank sensor to start.

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[hightime80]

Scan with VCDS and report back with codes.

[5ktq]

VAGCOM gave me an error for the cam sensor, signal too high.

Took the sensor off, looks alright. The connector was full of water, and both sides have some corrosion. Dried it out, scraped the contacts a bit and the codes / no start seems to be resolved, for now. I'm not sure that the cam sensor is essential for starting though..?

Suppose I should probably replace the connector, it's terminals are too hard to clean really in there..

[old guy]

If the cam position sensor goes out you have a 50/50 chance of the engine starting with every new attempt. Without input from the cam position sensor the crank position sensor can either fire correctly or 180° off.

[5ktq]

Ahhh interesting. So if the cam sensor is dead or unplugged, is the variable timing disabled? Or maybe it moves to a limp / default map or something?