Disco 2 Occasional Lumpy tickover

Hi
My Disco 2 TD5 has recently started cutting out or getting a really lumpy tick over that clears with revs. Happens just a couple of times a week. I suspected the fuel pump as when the fault occurs I cannot hear the fuel pump running and it’s normally quite noisy (Bearmach pump less than 12 months old) I’ve discovered that if I switch the ignition on and off about six times the pump usually kicks in. When the problem is happening I try to get the pump to self purge using the technique of 5 presses of the accelerator with ingnition on but that still doesn’t get the pump running. I have tonight changed the pump for a known good one but still it doesn’t always run when I switch on or self purge.
My question is should I hear the pump running every time I turn on? It used to.
Could the fault be with the pump relay.
Cheers Steve

Yes you should hear the pump every time when you turn ignition on, swap relay R1 with R3(headlamp wash) for test or put a new relay if you have, if still the same we'll speak then, do you have RAVE?