2008 2.0 tdi 170 cranks but won't start

[Kyle_471]

Good morning all,
I bought a 2008 2.0 tdi Pd170 DSG with 112k in January. Since day 1 of owning the car it's had a slight starting issue where it takes a couple of attempts at starting before it catches and starts. Stupidly bought it believing it had been stood a while so the battery needed jumping which worked first time.

Over the last couple of months this has progressed to the point that sometimes when trying to start it's almost like the battery is flat, it turns once and everything on the dash goes blank with no attempt to crank. Battery tested and is working fine. Immediately taking the key out and trying again it usually fired up.

This problem has got worse and worse to the point where it was taking me 4 or 5 attempts to start the car. Until 2 days ago when it just refused to start. Batter out and fully charged still nothing. Cranks well usually but doesn't fire, occasionally I still have the black dash as described above.

Over the last couple of months I've don't the following to try solve the problem.

OBDeleven readout showed crankshaft sensor fault.
This has been replaced.
Cleaned out the egr and intake flap whilst it was off, plenty of carbon in there.

fluids changed, filters changed.

HPFP rebuilt with new seals etc.
Lifter pump under rear seats appears to be working correctly. Turns on with ignition briefly and can prime for 30secs with OBDeleven.

Checked the resistance on all glow plugs which seem fine.

Checked all fuses and relays which all look good. Checked wiring which appears good, nothing looks loose or melted or shorting.

Tried both keys with the same result.

Really scratching my head with this, I've read through the forums and see people have had all sorts of different solutions which I've tried looking at on mine but none seem to work.
Does anyone have any suggestions based on the symptoms I'm having?

It's weird because when the car starts it runs fine and pulls like a train.

Thanks for taking the time to read my post.

[philipharmes]

If the dash is going blank during starting you have an electrical problem.

It sounds like the battery is on the way out or a poor conexion.

Check the battery terminals, make sure they are clean & tight.

Check the earth strap, make sure it is tight, no corossion where it bolts to the chassis & check the copper core hasn't got broken conductors due to fracture at each end.

What is the battery voltage after the car has been sat overnight ?

Does it start ok when the engine is warm ?

[Renars]

How was battery tested ?
First thing should have been new battery in this case.

[Kyle_471]

The dash going black is every now and then, I got the battery tested at a local garage who test it under load etc and confirmed it was good.
I can't remember what the voltage drop was overnight but I'm pretty sure the voltage stays on or around 12.6

The starting problems don't alter with a hot or cold engine

I'll have a look at earth connections tonight but I've already had a good look around before coming onto the forum.

Thanks for the suggestions 👍

[philipharmes]

If you don't find any problem with the conexions check the battery voltage while cranking.

It shouldnt drop below 10v.

Other possibility is a faulty starter motor with some shorted windings.

[Quatrelle]

As philipharmes #2 says, make sure the battery posts, especially, are really clean. Years ago a friend's car had the same problem - the starter turned the engine easily, so we wiped the posts till they were shiny, and the car started.

Might work for you.

[Kyle_471]

OK so I got home and checked everything. All connections look good, I had left the battery on charge just incase.
Took it off charge and connected it back up

Tried to start and cranking fine but didn't fire. After a couple of attempts it started however its now idling at 1200 and sounds slight rattly. Even when up to temp the idle didnt change.

[DieselMonster]

It shouldn't idle that high and engine shouldn't rattle either. Is it not throwing any codes up?

[simonson82]

My passat would randomly not start, just keep cranking. I read that if the starter doesnt spin fast enough then the fuel pump doesnt put fuel through to the engine. A replacement fixed the problems.

[DMitch16]

112k is in the range of an original LuK Dual Mass Flywheel failure. Could explain the rattling. As mentioned the starter motor could be a little tired and need cleaning (a lot starter motor problems I've tackled only needed them to be cleaned and regreased). One needed a new solenoid, one had a bad earth and another a loose power feed from the battery. Have had bad relays, over-running / failing to disengage and worn brush packs but apart from these few all the others have been restored to service with a clean. Must have cleaned 30 or so in the last 15 years.

Faulty ignition switches are common on these cars.