Pump could be "getting old".
Do the checks above first- filter,breather, relay.
Is there a filter between pump and tank? Always worth having to stop tank crud getting into the pump.
If not...fit one. Cheap and easy to do.
I did this on my 93 4/4 with cvh efi engine. My pump failed and was replaced by new....not repairable. Whilst doing it I drained and flushed the tank( crud came out), new main filter was fitted on engine end, in effect a system overhaul. New pump was Bosch version of the original. they are sealed units so not repairable.
Yours may repairable be so check the make etc.
Out of curiosity i cut open the main filter before disposal....the filter material was grey indicating it had caught stuff, reinforcing the advice to change them periodically. This stuff would have come through the pump hence a possible reason for failure.
