can a vacum line cause a fuel pressure drop from 76 lbs to 7 lbs on a 89 ford f150 laraint 4x4 ,302 fuel injected with dual tank
bypassed my fuel line. My line starts from my tank to the the fuel pump on the
rail. Still wont run. Replaced all new parts except fuel line.
No, the only vacuum line even closely related to the fuel system is the one on the fuel pressure regulator, and if it was bad or missing it would cause the fuel pressure to top out as high as the fuel pump could go. Now if the fuel pressure regulator stuck in full bypass it could cause a large pressure drop but you could recover that pressure by pinching off the return fuel line. Your right in that grey area of fuel pumps, does yours have lift pumps in the tanks and 1 large pressure pump in the frame rail, or high pressure pumps in the fuel tanks? Cause 7 lbs of fuel pressure sounds like lift pump pressure, not main pump pressure.
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