audi 100 1990 not starting when facing downhill

[tonos]

the car starts perfectly any other time, but when im parked on a steep downwards slope it wont fire up. It bump starts no problem but im snookered if someone is parked in front of me. Any ideas ?

[adamss24]

The non return valve on the fuel line may not work as should and the fuel drains away back into the fuel tank. Do you hear the fuel pump working when you turn ignition on ? It should stop after a sec. or so but if its working any longer, i would check the valve for dirt and the pump pick-up as well.