No fuel pressure
 

1998 jeep Cherokee 4.0 with no fuel pressure in the fuel rail but the pump is priming. Started idling all over the place then started surging, backfiring, then it started dying now it won't start I bought a new fuel pump but I haven't put in yet, could thus be the cause??!

Yup. Could be.

If it's running then there has to be fuel pressure.
Get a pressure gauge on it and do a leak-down test. The pressure in the rail should stay at 49 +/-5 psi for 10 minutes after the pump is de-energized.

My money is on at least 1 bad injector dumping fuel into the manifold.

It's not running any more it'll crank but won't start

I found out that the PO installed an 88 tank and pump in the Jeep which is a 98..I have no idea why, I can't contact him, I'm going to the junkyard today to buy a 98+ tank and pump assembly. After I bought a new pump for a 98 at $150 returned it then bought an 88 at $100 and now that's not working cause the wiring doesn't match and I can't get it to work no matter how I wire so I'm saying screw going for a loss on the 100 dollar pump.

That's a first.....

Geez, are POs never to be underestimated in their jury rigging?