won't take fuel

I have a 1997 transport 3.4 engine. It has an intermittent problem where it just won't take gas. ( push on gas and it seems to put it in a strain.) I have put a new fuel pump in it, as well as a tps sensor. the tech. said that he had the fuel pressure gauge ran inside and the pressure dropped to 38 psi. when he noticed it acting this way. Is fuel pressure to low?

I have had a similar symptom with my 3.8 and in my case the problem was with the Mass Air FLow sensor. This is the one responsible to deliver fuel according to the amount of air the engine breathes, not the TPS: TPS acts mostly as the acceleration pump in carburators: sudden changes in throttle position deliver an instant short duration burst of fuel..and that's it: in my case, pumping the throttle helped.

My MAF sensor "hot wire" was covered with a thin coat of clay following air filter failure (my fault...). Cleaning the hot wire with alcohol returned normal operation.

Now i'll tell you the rest of the story. there are no codes stored, I have tried "known good" and or new, fuel pump,tps,ignition module,crank sensor, egr,mass air flow,plugs,wires,fuel filter,cleaned injectors,cleaned throttle body,pcv,front and rear o2 sensors and air filter. tech removed eqhaust and checked the converter for signs of failure. he also checked back pressure and temp differential in the conv. I know that some of these won't cause this but i thought it couldn't hurt. the van and most sensors had 164000 miles on them. thats why i went ahead and changed them. the engine has 10000 miles on it. nothing i have done changes any thing other than the first 10 to 20 miles then here it goes again. problem has been there for nearly a year.

38psi of fuel pressure is VERY low. If your positive that the fuel pump and filter are ok, then I'd suggest a bad fuel pressure regulator, which is mounted on the fuel rail..