over the past 9 months i have had car skoda octavia vrs 170 2007 not starting usually only after a short journey just had injectors fitted as per recall so not that  scan at skoda says that imobilizer fault will not clear had it in to a diagnosis centre they say that because it starts eventually its not an imobilizer problem more like fuel preasure any help please

Probably a turbo failure

Probably a turbo failure

From an educational point of view can you explain how a failed turbo prevents a car from starting?

Stops/reduces airflow depending on how bad.

Boost pipe may also have come off.

Is it turning over OK when cranking?

Airlock or water in fuel system maybe?

Compression OK?

Electrical prob maybe? Is the battery OK - have heard of weird electrical probs caused by battery on its way out.

Edited 16 January, 201412 yr by FatblokeVRS

jimbojet - does it turn over but not start or does it do nothing when you turn the key?

Sheldon turns over but wont start. It does maybe on the 6th time then ok. this happens intermittantly maybe every 2days or maybe once a month

Camshaft sensor, fairly common problem on the PD170 engine, unfortunately costly to repair as it is behind the timing belt assembly so a new timing belt is required. Had the same problem on my old car. Get a diagnostics test run to confirm, as it should show up a fault code.

Although very unlikely, it might be worth checking the timing adjustment as it may have slipped. You would need diagnostics to check the front cam and then match the rear to suit. Have a google for PD170 torsion value.