Bronco Fuel Pumps

My 86 Bronco is not getting fuel to the injectors. Filter has been replaced. How do I decide whether the high pressure fuel pump or the low pressure pump is the culprit? The low pressure pump is in the tank and a much bigger pain to replace than the high pressure which is mounted on the frame rail. 5.0 L V8

suggest you get a Haynes Repair Manual and a fuel pressure gauge. it outlines a complete diagnostic procedure for determining what is faulty in the fuel system. Followed it when troubleshooting my problem...tidious, but very effective.