Good fuel pressure. engine turns will not start. runs if primed through trottle body.

Maybe a problem in the fuel pump circuit. Check fuel pressure with engine off, and key turned to on, not start. If no pressure, diagnose the pump circuit at the fuel pump relay. One terminal for the relay would be the power feed for the pump. The engine computer signals the relay on for 2 seconds with key on to prime the system, also signals during engine cranking.

The crank sensor is a good candidate. Pretty common failure on jeeps.
To clarify, the fuel pump is on all time during engine cranking, and during engine running. When the engine cuts off, the pump will also be stopped. But, you will not lose pressure in the fuel lines and fuel rail immediately. The check valve in the pump is supposed to hold fuel pressure in the system for a good time-about 20 minutes. The pressure should bleed off very slowly.

Your fuel pump and fuel system is probably good, but if you really lose prime (or pressure) that quickly, then there is a problem. Best way to check is with a fuel pressure gauge after the engine cuts out. Or, if you have the test port schraeder valve on the fuel rail (looks like a tire valve), you can use a screwdriver to press the center of the valve. If gas squirts out, you do have fuel pressure, prime is not lost, fuel system is good, and you can assume problem is in the ignition circuit, not a fuel problem. Probably the crank position sensor.
Good luck, Casey.

Sounds like a bad fuel pump.

this sounds like the timing is out, backfires, have you tried checking the plug wires, spark plugs, and did you reset the code after installing the MAF sensor?

The fuel pump might be working but it is not priming. When you turn on the vehicle, the pump sends fuel under pressure to the injectors, to "prime" or have fuel present to be able to start engine. Without it there will no fuel available to start it. You are manually priming the engine, and the fuel pump is taking over from there. Check connections to fuel pump and replace if necessary. It is not an inexpensive repair

There is a check valve in the fuel pump that sounds like it may have gone bad. Check the fuel pressure at the shredder valve, there should be 60 to 65psi during the prime and will drop 5 psi when the engine is running. Once the fuel line is primed, check to see how fast you lose your prime. Since you replaced your injection system, we can eliminate the fuel pressure regulator leaking which was common on the injection system your truck run's on. If the fuel pressure drops fast then it's going to be a bad check valve at the fuel pump and it may be time to replace the fuel pump it self. Good luck and hope this helps. Note: do not try to start the engine with putting gas through the throttle body, it's been know for small fires to start and burn the spider injectors. 

Check the trottle body postioning sensor...

i have the same problem on a 98 jimmy 4.3 4x4.
i replaced the fule pump and have good pressure.
new wiers & coil (good spark) no MIL & no codes.
will only start when primed. it will run & drive all day
with no problems.
but once it has been turned off (warm or cold) i will
have to prime it once again to start it.
i have another engine that was in it before it spun a bearing.
it ran fine so i know all parts are good.
i swaped the mass air flow and throttle body but i still have
to prime it everytime to start it. am i forgetting something?
should i swap out the intake with the injectors?
any help would be sweet. thanks.

Did you change the fuel presure regulator located in the throttle body?

93 GMC PICKUP WONT START REPLACE RELAY SWITCH'FUEL PUMP' MODULE CONTROL BOX' POUR GAS IN TROTTLE BODY TRY TO RUN