VW UP 1.0 2012 Turns Over But Won't Start

[dilligaf76]

I friend of mine has got this car which was working perfectly fine until they decided to remove the dash and add aftermarket lights and switches by splicing into the wires.
Since putting everything back it won't start. It turns over but it seems there is no spark to the plugs.
What on earth could they have done to cause this?

[paul_c123]

Firstly, how did they determine there is no spark?

For general direction, its worth a diagnostic scan but it sounds like the immobiliser wiring has been disrupted. But it could be 101 things if they've been thrashing around behind the dashboard.

[dilligaf76]

Well we know it’s getting fuel so if there was a spark it would fire.
Apparently someone did put a diagnostic machine on it but it didn’t give any codes to sag what was wrong.
Is there away to reset the immobiliser providing it is that?

[GreenV8S]

dilligaf76 said:

Well we know it’s getting fuel so if there was a spark it would fire.

That seems like quite a big assumption.

If you haven't proved you have an actual spark, I suggest you do that.

The history strongly points towards it being an electrical fault, but it would be much easier to track down if you can find out whether the ecu is giving it fuel and sparks.

[dilligaf76]

I’m guess I could take a plug out and check it…

[Feirny]

Mine did this, and after chasing it for a good few days it turned out to be the coolant temp sensor of all things!

[dilligaf76]

What the coolant sensor stopped it from starting?

[stevemcs]

Surely it has to be related to something they have done ?

[GreenV8S]

Feirny said:

Mine did this, and after chasing it for a good few days it turned out to be the coolant temp sensor of all things!

Many engines can be a pig to start without the correct enrichment.

That's why I suggest starting by investigating the basics, avoiding assumptions.

[Feirny]

dilligaf76 said:

What the coolant sensor stopped it from starting?

Yep. It was a very bizarre one and random suggestion from a customer that prompted me to change it, I got the part through my work at £4 and it fired straight up first time and ran perfectly after.

[Belle427]

If the instruments were removed on some Vag stuff it does something with the anti theft system, i seem to remember having an issue on a Seat some years ago. I cant quite remember what i did, maybe try disconnecting the battery for 10 mins or even using a code reader to clear codes.

[E-bmw]

dilligaf76 said:

I friend of mine has got this car which was working perfectly fine until they decided to remove the dash and add aftermarket lights and switches by splicing into the wires.
Since putting everything back it won't start. It turns over but it seems there is no spark to the plugs.
What on earth could they have done to cause this?

My best initial suggestion would be to go back over the job with a fine tooth-comb and even better return it to the way it was initially.

If that works get them to take it to an auto-electrician next time they want additional lights.