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Is a very known topic that the Vortec spider injection system is prone to leak inside the intake and has problematic poppet valves I found exactly that being the problem of all my misfire codes and rough running issues replaced the spider injection with new current updated part which gives actual fuel injectors at the bottom of each tube my system now stores and holds pressure without hardly any leak down..

Now the real question I read everywhere that fuel pressure on vortex should be 6265 psi at Prime and full running condition or else vehicle will not start this is false! My vehicle now runs and starts at turn of key exactly the way it should and I am only producing 45 to 50 psi at prime and runninG..Fuel pump is one year old and the new fuel injection spider system is 3 days old so fuel pressure regulator is also knew as it comes part of the new injection system..When plugging off the vent back fuel line my pressure tags out the gauge so I know my fuel pump is capable of producing 90 psi or higher.

So why am I only producing 45 - 50 psi in my normal operation?..I have absolutely no leak down pressure and holds solid and firm at 45 psi for a long time after the key is turned off I also have 12 volts or more at the pump and confirmed all good grounds..Any takers on this one?..The truck runs and starts very well but I can still feel a slight miss not a complete smooth rhythm so I feel it may be due to the low fuel pressure..What does map sensor have anything to do with fuel pressure regulation seeing how the fuel regulator is inside the intake manifold on the spider injection system using internal engine vacuum to operate and MAP sensor reads these values?

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Could be that your gauge is off a bit. I've heard lots of people say there's a fine line between these things running fine, and not running at all when it comes to fuel pressure. Just 5 psi too low and it won't even start.


I know the MAP plays a big part in how these newer engines run. Early FI relied heavily on the MAP sensor for fueling. A vacuum leak in the hose to the sensor on Fords would make them run pig rich - rough, black smoke, barely idling. Knowing vacuum levels in the intake is pretty important - without that parameter, the computer wouldn't know how much of a load is on the engine.

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Maybe I am not understanding what you wrote, but to me, you answered your own question. When you block the return line your fuel pressure goes up past the limit of your gauge. Pretty sure that your return line also has a regulator on it, that is controlled by vacuum, as well as a spring internally. The internal spring will be what sets the maximum pressure in the system, the vacuum line will be what is used to control fuel pressure under different loads. The more you depress the throttle, the lower the vacuum, making the spring control fuel pressure(raising it). Throttle closed will give max vacuum, and that will make the regulator dump more fuel back to the tank, reducing fuel pressure.

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