Fuel Flowing Uphill [or not]

[ShinyF1]

I've had an issue starting my car this morning when it was left parked facing uphill overnight.

It has happened occasionally in the past but I'd always put it down to a virtually empty tank (not good practice I'm sure).

But today, half full tank and it wouldn't start straight away this morning. It eventually fired up after three turns of the key when I'd almost given up.

Is it normal for fuel to drain away from the system like this or do I have a leak in the system somewhere?

 

[whitenemesis]

'O' rings in the fuel pipes have hardened and are letting in air. Check for air bubbles in the clear pipes in the engine bay before the first crank.