GM-GMC: fuel pump problems, fuel pressure regulator, chevy c1500

Question
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Followup To
Question -
it is a 97 chevy c1500 175,000 miles 350ci  my truck had failed to start after i tried to start it to quickly after shutting it off. i did not hear the fuel pump anymore so i replaced it and the filter. it ran 10 miles fine and then all of the sudden would only run not accelerate. it would die when you stepped on the gas too much. i could go from 0-50 gradually(very slowly) so i drove it home lightly stepping on the pedal too much and she dies. i checked the fuel pump pressure at the service spot in the line it is 55lbs when i turn the key on then the pump stops and it drops to 12. then it is 50-52lbs running the engine. i was told it may be a fuel pressure regulator or throttle sensor. now i start it and it dies when i step on the gas. any help?
Answer -
Bill,  

  You did not mention witch fuel injection system you truck uses. I'm guessing you have a port injected vortec motor since the TBI trucks use only 9-13 PSI Fuel pressure. It sounds like you have good pressure I'm not sure of the actuall specs, but I would be concerned about the drop to 12 psi when you shut the key off, a rule of thumb on fuel rail pressures is its should hold 20 psi for 20 minutes and an abrubt drop that you have could mean that the fuel is leaking back into the tank or that you injector assy. in you intake is leaking. This could explain the stall, no power because while its running its dumping in gas like crazy keeping the motor extreemly rich on the verge of stalling. Then when you open the throttle adding even more gas it stalls the motor. This is only a guess since I don't know what Inj system your truck has but Gm's Injector/poppet valve inj.assembly is know for problem similar to this one. Let me know your specific inj. system and I'll be able to help you further.



follow up

it is a vortec 350  engine. i can increase the rpm very gradually. it acts just like the old cars did when the accelerator pump went out. the check engine light does not come on at all ecept when not running. what you say could be correct as the old pump could of been a little week and the system was not used to the increased pressure of the new pump. unfortunatly i did not have a "before" pressure. i was hoping to repair it myself but from what you say it sounds like more specilized equipment. would the fuel pressure regulator introduce to much gas?
thanks for your help
bill

Answer
bill,  

 the fuel injector and regulator on this truck is a unit witch sits inside the intake plenum. usually the injector will start to leak or the regulator. Regardless the fix is a new assyembly. The injector assy. have 4 lines and poppet valves on each side. these poppet  valves have a tendancy to stick open or crack aswell. Sometimes you can remove the MAP sensor on the intake plenum and take a look inside with a flashlight if its all wet in there you've definetly got a leak. Only other way to inspect the injector is to remove the plenum, not too big of a job but you will neet a plenum gasket set. Hope you get it figured out!