B4000 won't start!!!

[QMRacer18]

Okay guys, I'm new to this forum but, I've looked around and you all seem pretty helpful. I have a '94 B4000 auto, ext. cab, pwr everything. It was running rough origionally so, I tryed a few things. I cleaned my ICV and mass airflow (it was throwing a 157 - still is) and replaced the gas tank filler neck. I put it all back together and it wouldn't start. I tested the fuel pump, reset the fuel inertia switch, checked every fuse in the truck, my relays (used up a set of batteries in my multimeter checking wires) and I have fuel pressure at the fuel rail. (don't have a guage so I don't know how much.) The truck has since thrown a 543 (fuel pump circut open) - that went away after removing and reinstalling the pump??? I know that code means it won't run 99% of the time, but it hasn't come back. 122 (TPS low signal strength) - replaced the TPS and that went away. Still won't start. The only code left is the 157 but it ran with that before. Spark is good on all cylinders with new coil pack, plugs, and wires (on the truck before I bought it) The thing that gets me, is that the truck won't start even with starting fluid. I hunts and tries to catch no matter what, but just won't do it!! We tested the EGR and that's good (I don't know if that would keep it from running anyway) We read that the camshaft position sensor could be it or the fuel pressure regulator..... I'm very confused. Mabey the PCM? (but it shoots codes ok) and, yes the three codes I had origionally did come back on after resetting the PCM so we deffinatley did get rid of 543 and 122. Help!!! I'm at an absolute lose. AllDataDIY, 2 books, and lots of online reading.... Still nothing. Thanks in advance for any help guys!!!

 

[dock83]

This may help catalytic converter or muffler pluged un bolt it and see if it will start no cost if your bolts come out fine flange should fall apart. Back pressure is a b***h worked on my dirt bike when the muffler was pluged worked at it for a month.