Passat 125tdi starting problem

[WestcoastPete]

Hi

I've just searched up on this and have a few leads, but thought I'd post my specific situation anyway because it's not exactly the same as others I've found.

My '08 Passat wagon with the 125kw TDI engine has just hit 150,000km and has been brilliant. Recently it developed a starting issue. We'd driven it to the pool in the morning no worries, but then when I went to run an errand soon after it really struggled to start. It cranked fine and for ages. Sometimes it would cough like it as going to start but it didn't, then after a fair few goes it did. It did the same thing during the errands so I drove it straight to the mechanic and left it with them, fearing getting stuck somewhere. They couldn't find a problem but the fuel filter was pretty grotty so they replaced it. It was fine after I picked it up for a bit, but now it's doing it again, but intermittently.

So, it cranks powerfully for ages. I'm surprised by how long it will crank for without the battery slowing down. Sometimes it coughs like it's starting but doesn't start. While it's trying to start I can hear a clicking solenoid under the bottom of the dash (this may or may not be relevant). Once it starts after struggling for ages, the cruise control doesn't work. If it starts without struggling, the cruise control works fine.

From my research, I'm thinking it might be the starter motor not cranking fast enough, so possibly a new starter would solve this. Any other thoughts? Attached is a video of it trying to start

Passat B6 125tdi struggling to start - YouTube

[kleung]

They couldn't find a problem but the fuel filter was pretty grotty so they replaced it. It was fine after I picked it up for a bit, but now it's doing it again, but intermittently.

If it was fine for a while after the fuel filter was replaced, is it possible that you've got a tankful of filthy fuel, and the new filter is clogged again?

From my research, I'm thinking it might be the starter motor not cranking fast enough, so possibly a new starter would solve this. Any other thoughts? Attached is a video of it trying to start

Don't do the parts cannon thing. You or your mechanic need to do some diagnostics first. When you took it to your mechanic, did they mention if they scanned your car for codes?

My money is on a fuelling issue. Lack of fuel pressure, either because of a clogged filter, or a failing fuel pump?

[neil]

Had similar issue on jetta TDI , if you'd been driving a while then stop and then try to restart after say 5 minutes it would crank over and not fire , then would start ,was intermittently , been a few issues on here over the years like that and turned out to be low battery , but mine only resolved with a new starter motor at 250,000km. now with over 300,000km and never had an issue since it was replaced.
If it does it again try holding foot on accelerator or pump accelerator when you try start engine, that worked for me sometimes.

I think I put up a post about my issues years ago , it had been doing it for many years way prior to the replacement starter motor.

[Lucas_R]

Have a google of this issue, its pretty common on the 2.0TDI engine. Various reasons it could be, but some of the info on Google should give you some things to mention to the mechanic to check.

I'd start with getting your battery health tested. Anything under 12.5v and its time to replace it.

Also apparently if the starter motor is getting weak (or not getting enough power from a dying battery) and it cant spin at 280rpm then the injectors wont fire and the engine wont start.

2.0L BKD - difficult to start hot

2.0tdi vw hard to start - Google Search

[WestcoastPete]

Thanks for the replies. It's still doing it but it hasn't not started yet. We're going away for a couple of weeks soon so I'll drop it into the mechanics while we're away.

[nermal]

We had a similar issue a couple of years ago with our 2008 125TDI. I think it may have been worse on cold mornings and if the car had sat for a while.

Tried a new battery (was testing low) before replacing the starter motor. The starter motor made a big difference. I want to say crank angle sensor too, but can't seem to find anything in my email history other than the starter motor...

[WestcoastPete]

OK so a little update on this.

This issue was persistent. If I was going on a bunch of errands it would start fine straight away and for the next few stop and starts. Then it would start doing the thing where it turns over totally fine but wouldn't start straight away, then it would. This would get worse, so the period of turning over would get longer before it started. But it always eventually started. (I never just let it turn over and over. I always give it a rest every 5secs or so).

My research pointed towards the starter motor but not definitively. I replaced it anyway and the new one certainly seems to be more powerful and it turns over faster. The problem isn't solved though and it still gets harder and harder to start on errand runs. A couple of things I've noticed that may or may not be relevant are that, there's a clicking sound near the key when it's trying to start but can't, and the cruise control doesn't work if it's started after having difficulty starting. If it starts straight away, the cruise control works fine.

Any other ideas?

[Hillbilly]

BATTERY for sure not cranking fast enough. Was on mine anyway after 4.5 years of short runs battery was stuffed. Do you get a dashboard full of lights at times, another battery problem indicator as is clicking because of not enough current. As per what Lucas says is a good start

[WestcoastPete]

BATTERY for sure not cranking fast enough. Was on mine anyway after 4.5 years of short runs battery was stuffed. Do you get a dashboard full of lights at times, another battery problem indicator as is clicking because of not enough current. As per what Lucas says is a good start

Na no lights. Battery is new, and I keep it topped up. As I say, it's cranking fine. Way faster with the new starter than it was. I'm more inclined to think it's a fuel thing now too. Maybe a leaky injector seal? Fading fuel pump of some sort?

[sn809]

If u use a vag com cabke and run the fuel lifter pump(inside fuel tank) a few times and the car starts its the fuel lifter.

On a new battery you can also insert and remove key to on position upto 3 times till and then start the car.

If car starts then its likely a fuel pump issue(inside tank). Its a common issue in a tdi