2005 Passat TDI wont start when plugged in

The car runs great, starts great when warm and starts good when cold. When it gets really cold and i have to plug the car in..-20 celsius it will not start, just cranks. The CTS is thinking the car is warm because the coolant is warm, so it doesnt do a cold start....longer glow plugs, timing. Is there something wrong with the coolant heater, is the CTS suppose to be getting heated? Is there something else wrong somewhere? I unplug the CTS and it does a cold start and starts great. I dont want to be poppin the hood everytime i start the car. Any help would be appreciated.

So we understand correctly, at -20C it just cranks and won't start?
Have you tried cycling the glow plugs a few times before startup?
What type of heater are you using, and how long is it active prior to your attempts to start?

STDOUBT said:

How long is it active prior to your attempts to start?

Click to expand...

This is the key question... 'cause it's actually worse to only plug it in for a few hours when it's -20C out... for the reasons you've discovered. The coolant around the coolant temperature sensor is being warmed, but not enough time has gone by to fully warm the block too.

Every car responds a bit different to the coolant heater, depending on type, but on my car if I can't plug in at for at least 5 hours in the middle of an Edmonton winter I don't bother. More than 5 hours heater run time seems to always be enough time to warm the block up properly.

There's a theory in a situation where only part of the coolant is heated enough cranking will circulate the coolant, blend it all together, and eventually the temp sensor will get an appropriate reading. Dunno how much cranking that would be... but short bursts so that the ECU keeps making an initial starting calculation are probably a good idea.

If you're having this particular problem *and* the car has been plugged in overnight there's probably something else going on, either with the heater install itself (positioning is important for good convection) or something more basic like a compression or fueling issue.

The car is plugged in all night ..roughly 9 hours...when i lift the hood to unplug the CTS the engine is hot, really hot. If it does start after many minutes of cranking it, the vents blow warm air. Ive tried the cycling of glow plugs, but doesnt make a difference. I just went out and started it, unplugged for 5 hours in -20, and it started right up. Glow plugs came on for 3-4 secs and high idle kicked in. It also starts great whenever i shut it off for a minute or 2 so normal warm starts are excellent. As a sidenote..my 2004 Jetta TDI did the exact same thing until i parked it for good.

Hmmmmm... strange.... if the block is hot then so much for the "coolant hasn't had time to circulate" theory. Blowing warm air is the double-tap for that theory.

Does the dash gauge read that the coolant is partly warm as well?

In any event I'd be inclined to get a scanner and see what the CTS is actually reporting to the ECU after being plugged in all night. When they go south they often start to lie (as opposed to fail outright) which means no CEL and often weird starting symptoms.

I do have VAGCOM so i can plug that in. What do you recommend me checking, and when...car cold, car warm? This weekend im putting a bigger battery in, but it turns over really well when plugged in.., a new crank sensor and cam sensor. I might as well put in a new CTS sensor while im at it. We are going to check the timing also. Im hoping that maybe a couple sensors are just weak and causing a combined problem. Any other suggestions? Thanks

Prefect... yeah, fire up your VCDS and see if the coolant sensor sees ambient properly with the engine stone cold. Then check again after she's been running a while and the dash reads 90, and then again after she's been plugged in over night. That will give you 3 data points to access if the CTS is telling the truth.

That said, they are easy to swap out and cheap too... but I always like to gather some evidence before the march to the gallows?!

Oh, and with VCDS hooked up for sure scan the engine for codes...there may be pending ones that haven't turned on the CEL.

Your 2005 has a PD engine and it does its own ignition timing... nothing to adjust... dunno if you can even measure it. It's possible to measure the cam/crank timing ("torsion"), but I'd be hard pressed to understand why the car starts so well in most situations if there was an issue with the cam timing.

Crank sensor is the usual next suspect for a hot start issue... but you didn't have this problem in the summer, right, or if you try to start the engine when it's hot on its own?

I decided to double check my timing torsion number when we plugged the vag com in. It was at a whopping-4.4...thats not good. So my son and I rotated the cam some and on first crack hit 0.0 The car seems to have a little more pep now and we havent had the chance to test it to see if starting has improved.
On a side note, my son noticed that the turbo graph didnt look right. The actual turbo line was a good bar line away from requested...it followed it perfectly...just always low. Its a brand new turbo 2 months ago. Would the actuator arm need lengthening or the stop nut for the vane arm need moving. I hope everyone understands what im talking about. Thanks
Oh , Vince what am i exactly looking for in temp readings...the only reading i found was 5 degrees....it was -19 outside.

Never trust 0.0 for torsion always set to something besides 0.0 since that is also the value when it is out of range.

I read this thread and I'm curious. Do 05 jetta tdi come with a block heater?? Is it standard on these cars??

Just an update. After setting the timing to +.5 and installing a new crank position sensor, the cars starts instantly and all the time. It also idles incredibly well and transmission shifts much nicer. I thought the car ran good before, i am now shocked at how smooth it runs after a new CPS.
There is no block heater on the car, i have a coolant heater installed. Thanks All