non return valve for fuel line

which line would you put the non return valve in ?
would it be the supply line from the tank to the filter housing or the from the filter to the pump ?? .
reason for asking my disco has the a fault.
i.e some mornings it will start fine heater light out touch key and away fine other mornings go out let light go out and you have to turn it over until it primes and then away it goes .
starts fine every time if I park it facing down hill if parked facing uphill for say a hour you got to let it turn over for a while .

Could be the lift pump.
Its fitted with non return vlaves that harden over time and then fail to seal properly.
i discovered this as mine (a 110 but same sort of pump) was ok but then wouldnt prime, so stripped pump sealed valves with vaseline and it primed and started straigt away.
Have since replaced pump as they are cheap.
There maybe another prob but sounds like this could be the issue.

been parked up for 2 days went out about 30mins ago and fired straight up very baffling

hodge911 said:

been parked up for 2 days went out about 30mins ago and fired straight up very baffling

Click to expand...

Could depend on how much fuel is in the tank