991.1 Carrera 4 - intermittent starting problem

[Ledlights]

Hi All,
I used my C4 the other night for a number of local trips. On one occasion, I parked the car but when I went back to it 5 minutes later, the car cranked well but wouldn’t start.
There were no codes, no CEL and an hour later the car started as normal. It’s been fine since but could be embarrassing if it happens in traffic. Anybody had anything similar?

 

[jetguy71]

Could the immobiliser. Please search this site for the threads. Apparently, it commands the Starter and Fuel Valve to prevent "unauthorised starts". Can't just unplug it. Has to be coded off. Also, a Vodafone Tracker may be installed and associated dongle is the key. Occasionally the dongle batteries get weak.

Been down this frustrating road. Keep calm and trawl the forum.

 

[Ledlights]

Thanks for your reply. AFAIK the car doesn’t have an immobiliser. The common problem seems to be a failing battery but in this case the starter was spinning freely, so not that either. My thoughts were either a sensor (crank, cam etc) on the way out or the fuel pump relay as there weren’t any DTC codes but purely a guess as it was fine an hour later. Any ideas welcome…

Thanks,

Steve

 

[DRZ911]

Have had a similar thing happen the day after washing my Cayman (no Vodafone tracker). Cranked, but wouldn't start. Left it for a bit and it started OK. Someone suggested damaged coil packs at the time. Dealer checked and said the packs were fine. The same issue has happened a further 2 times. Again, both after washing.
Also, should look at battery. Should be 12.54V or above without engine running (this is classed as 80% state of charge).

 

[Johny99]

Will be hard to tell without interrogating piwis and checking values etc.

I did a number of stop start drives in the summer, the last time I jumped back in and cranked it she wouldn’t start and then had a load of error codes, transpired to be a short in my dme needing replacement.