1993 Ford ranger 4.0 OHV. Fuel pump runs continuously (key on truck off) I confirmed it’s not a computer or electrical issue through testing different computers, pumps, giving it 12 volts and doing the jumper wire in the relays place, and grounding through the obd port, inertia switch is good. I’ve replaced the fuel pressure regulator and a lot of sensors including the crank position sensor. I’ve only read about my same issue in one other old forum but no one said how to fix the issue, so if anyone knows what I should do or what to fix when the trucks regulator doesn’t maintain pressure at the fuel rail and letting everything go back down to the return line (because I can hear it doing so, and also opening the fuel pressure test valve stem thing it just lets gas run out rather than having pressure) I would greatly appreciate it and the only reason I care about it running continuously is that it’s not able to properly build pressure to prime to therefore start on its own without ether. (still runs perfectly with some help from ether)

 

1993 Ranger should have 30-35psi running pressure at the engine, then hold pressure above 15psi key off

FPR(fuel pressure regulator) is the only thing that restricts pressure, its set for 43psi, but with engine vacuum it maintains about 30-35psi
Fuel pumps can do 80+psi unregulated
So there will always be flow thru the FPR and back to the tank in the return hose when engine/pump is running

The IN fuel line comes from fuel filter and goes directly to fuel rail
The Return line is on the FPR

The computer Grounds the FP relay to activate it, it then sends 12v to inertia switch and then to fuel pump
Computer only grounds the FP relay for 2 seconds with key on, if FP relay stays on after that the wire to pin 22 on computer is shorted to ground or bad capacitors in the computer

The Fuel Pump slot in OBD1 connector is the GROUND for FP relay, its connected to pin 22 and FP relay's ground
With key on, after 2 seconds, that slot should show 12volts on volt meter, that's the voltage passing thru the FP relay's coil because it not grounded