Am at wits end here, was driving along, came to a junction and car just cut-out on me. When I tried to turn it over it cranked but wouldn't catch, after about 6 attempts battery died, towed to a friends garage connected to a boost pack and she started first time. So changed battery thinking it was a poor battery. Car drive home about 30 miles no problem. Next day popped to shops and same thing happened, got it home and about half an hour later it started again no probs, engine sounds sweet. Battery measured 15 volts and goes up to 17 when running. But car cuts out again after about ten minutes whether moving or just idling in the drive. It cuts out without spluttering or any sign. It'd like ignition us just turned off.

Timing belt and water pump done about 3k miles ago, but car has ran perfect until now.

Any ideas on what this is much appreciated

if battery measures 15 volts and 17 when running the Alternator is at fault, should only 14,2 maximum

Sorry meant to say battery i have in is slightly bigger than standard, am waiting on proper battery but am confident alternator is OK

Update I'm getting this code from my obd thing P0011 power train, could it be crankshaft sensor??

Possible Symptoms

• Power Loss

Possible Causes

• Camshaft Adjustment Valve 1 (N205) faulty
• Fuel Pump Relay (J17) faulty
• Mechanical Timing not correct, including Chain and/or Belt timing.

Possible Solutions

• Check Camshaft Adjustment Valve 1 (N205)
• Check Fuel Pump Relay (J17)
• Check Mechanical Timing

Special Notes

• When found in Engine: 4.0l W8
  • Check TPL 2010059(RoW)
    • Check/Replace Oil Sieve in Timing Case (Camshaft Adjuster)

I was going to say fuel pump relay dodgy, before I went out, so I would start there first if you can get one to swap, although the high line voltage may have killed the original due to overcharging from the alternator.

Thanks a mill folks, I'll start with these bits, although u may be be right about battery, this all started with standard 12v in the car, just before it dies there is a little click under steering wheel, is that where relay is located

15 volts from a 12v battery?  is your multimeter up the duff?

Very possibly, gettin proper battery tomorrow, but can't figure out how this manifested on its original battery

Yep, scrap those voltages, was bogey meter, battery at 12.4 climbing to 14.6 when idling

Sorted, new crankshaft sensor, now she's brand new

That is good to hear.