X2 ( well 3 , actually) on the electric fuel pump. If the filter is not clogged or water logged then a pressure test consisting if cranking pressure and running pressure will need to be performed. You'll want to compare running pressure with fuel,pressure regulator line on and off while running to see PSI difference. Can't get to my books now for specs as my library is constantly being moved from one place to another while interior home work is being done but that's obtainable on line so not to worry. I could say that if your not getting a consistant reading in every attempt to,start the engine , the pump is bad or there is a leak in line or in the tank sending unit connections . I cannot remember if the YJ 's sending unit is easily accessible as is the XJ but if so and you want to take a peek at the rubber hose that connects the electric pump to the sending units metal pressure line for a,rupture , I'd say go,for it. But if you've got to drop the tank , you'll want to be sure the pump,is bad before going through all this labor. If it's the original pump with high mileage and much driving below a quarter tank and lack of filter changes , it may be on its way.
See if auto zone can rent you a fuel pressure tester and try getting readings. Whether a 2.5 or 4.0 , the reading is taken from the Schrader valve on the fuel rail so not a huge hassle of pluming in test adapters like a throttle body . Look for consistency in psi in several,starts/ cranking and psi readings running with/without fuel,pressure regulator line on. Cranking psi should get up,close to running ( 40 psi or so ) but the first reading is what tells how good or bad the pressure is when key turned on and cranking begins. If pressure builds in steps then a restriction( clogged filter), leak or outright bad pump is probable. Let's check this before we start pointing at crank or cam position sensors first. But from your post , priming with the key sounds like fuel pump problems. Please post back when able.
