1991 F 250 5.0 was running not now has good pressure at the fuel rails nothing thru injectors

If the injectors are stuck open, the control to them is faulty.
Probably a bad earth wire on the ECU for the engine management.
Unplug the injectors to check they hold pressure. If they, do look for the cause. If they don't, don't waste your money, rebuild the engine.

By fuel reset do you mean inertia fuel cut off switch ? Why did you change the fuel pump ? Are you aware of the fuel pump driver module ! Your vehicle has a electronic returnless fuel system . It is computer controlled , has a fuel rail pressure an temp. sensor .
The FRPT sensor measures the pressure and temperature of the fuel in the fuel rail and sends these signals to the PCM. The sensor uses the intake manifold vacuum as a reference to determine the pressure difference between the fuel rail and the intake manifold. The relationship between fuel pressure and fuel temperature is used to determine the possible presence of fuel vapor in the fuel rail. Both pressure and temperature signals are used to control the speed of the fuel pump. The speed of the fuel pump sustains fuel rail pressure which preserves fuel in its liquid state. The dynamic range of the fuel injectors increase because of the higher rail pressure, which allows the injector pulse width to decrease.
Inertia Fuel Shutoff (IFS) Switch The IFS switch is used in conjunction with the electric fuel pump. The purpose of the IFS switch is to shutoff the fuel pump if a collision occurs. It consists of a steel ball held in place by a magnet. When a sharp impact occurs, the ball breaks loose from the magnet, rolls up a conical ramp and strikes a target plate which opens the electrical contacts of the switch and shuts off the electric fuel pump. Once the switch is open, it must be manually reset before restarting the vehicle. Refer to the Owner's Literature for the location of the IFS.
The FPDM receives a duty cycle signal from the PCM and controls the fuel pump operation in relation to this duty cycle. This results in variable speed fuel pump operation. The FPDM sends diagnostic information to the PCM on the fuel pump monitor circuit. For additional information on Fuel Pump Control and the Fuel Pump Monitor, refer to Fuel Systems in this section.
Electronic Returnless Fuel System (ERFS) The electronic returnless fuel system consists of a fuel tank with reservoir, the fuel pump, the fuel rail pressure (FRP) or fuel rail pressure temperature (FRPT) sensor, the fuel filter, the fuel supply line, the fuel rail temperature (FRT) sensor, the fuel rail, the fuel injectors, and a Schrader valve/pressure test point. For additional information on the fuel system components, refer to Engine Control Components in this section. Operation of the system is as follows:

1. The fuel delivery system is enabled during crank or running mode once the PCM receives a crankshaft position (CKP) sensor signal.

1. The fuel pump logic is defined in the fuel system control strategy and is executed by the PCM.

1. The PCM commands a duty cycle to the fuel pump driver module (FPDM).

1. The FPDM modulates the voltage to the fuel pump (FP) required to achieve the correct fuel pressure. Voltage for the fuel pump is supplied by the power relay or FPDM power supply relay. For additional information refer to Fuel Pump Control and Fuel Pump Monitor.

1. The fuel rail pressure (FRP) sensor provides the PCM with the current fuel rail pressure. The PCM uses this information to vary the duty cycle output to the FPDM to compensate for varying loads.

1. The fuel rail temperature (FRT) sensor measures the current fuel temperatures in the fuel rail. This information is used to vary the fuel pressure and avoid fuel system vaporization.

1. The fuel injector is a solenoid-operated valve that meters the fuel flow to each combustion cylinder. The fuel injector is opened and closed a constant number of times per crankshaft revolution. The amount of fuel is controlled by the length of time the fuel injector is held open. The injector is normally closed and is operated by 12-volt VPWR from the power relay. The ground signal is controlled by the PCM.

1. A pressure test point valve (Schrader valve) is located on the fuel rail and is used to measure the fuel injector supply pressure for diagnostic procedures and repairs. On vehicles not equipped with a Schrader valve, use the Rotunda Fuel Pressure Test Kit 134-R0087 or equivalent.

1. There are 3 filtering or screening devices in the fuel delivery system. The intake sock is a fine, nylon mesh screen mounted on the intake side of the fuel pump. There is a fuel filter screen located at the fuel rail side of the fuel injector. The fuel filter assembly is located between the fuel pump and the pressure test point/Schrader valve.

1. The fuel pump (FP) module is a device that contains the fuel pump and the fuel sender assembly. The fuel pump is located inside the reservoir and supplies fuel through the fuel pump module manifold to the engine and the fuel pump module jet pump.

1. The inertia fuel shut-off (IFS) switch is used to de-energize the fuel delivery secondary circuit in the event of a collision. The IFS switch is a safety device that should only be reset after a thorough inspection of the vehicle following a collision.

Go to you tube , there are videos how this system works an to test it .

Are you getting power and a ground signal to the injectors ?

Well code 171 means the O2 sensor is telling the computer the fuel mixture is too lean and the computer can not make it go rich by increasing on time for the injectors.
The problem could be the O2 sensor, or low fuel pressure, or several other factors.

LOOK ON THE FUEL INJECTORS RAIL YOU SHOULD SEE A BLACK CAP THAT LOOK LIKE A TIRE AIR PRESSURE STEM REMOVE THE CAP AND FUEL PRESSURE REGULATOR IS THERE

Pull your O2 sensor and see if it fires. If so you have a clogged cat.

In your case the pressure sensor is faulty and needs to be replaced. 1) Stores pressurized fuel (25 to 180 MPa) that has been delivered from the supply pump and distributes the fuel to each cylinder injector. A rail pressure sensor and a pressure limiter valve are adopted in the rail. 2) The rail pressure sensor (Pc sensor) detects fuel pressure in the rail and sends a signal to the engine ECU, and the pressure limiter controls the excess pressure. This ensures optimum combustion and reduces combustion noise. ---- Rail • The rail is mounted between the supply pump and the injector, and stores the high-pressure fuel. --------- Injector:-------- • This injector replaces the conventional injection nozzle, and achieves optimal injection by effecting control in accordance with signals from the engine ECU. Signals from the engine ECU determine the duration and timing in which current is applied the injector. This in turn, determines the quantity, rate and timing of the fuel that is injected from the injector. ------------ Rail Pressure Sensor (Pc Sensor) 1) The pressure sensor detects the fuel pressure of the rail, and sends a signal to the engine ECU. The sensor is made from a semiconductor that uses the Piezo resistive effect to detect changes in electrical resistance based on the pressure applied to the elemental silicon. In comparison to the old model, this sensor is compatible with high pressure. ---------- There is a service manual for how the fuel rail sensor and fuel system works.Its for mitsubishi L200 4D56.----------- Click this link for referring the service manual:--- http://technoanswers.blogspot.com/2011/06/service-manual-for-mitsubishi-l200-4d56.html ----------- This should help.thanks.Helpmech.

Failure-to-start scenarios are often an issue of "fuel or spark?"

To check fuel pump, install a fuel pressure gauge on the Shrader valve connector on the
fuel rail, reading ???? - I couldn't find the spec for nominal fuel pressure.....

One good source of diagnostic info is your car's computer - commect an OBD-II code
reader to your car's OBD-II port and ask the car what it thinks it wrong - its capable of
posting 100s of possible error codes, any number of which would/could implicate a fuel
system component. Here a (very) short list of possible computer codes your car's computer
may currently be posting:

error code meaning
--------------- -------------
P0107 MAP (manifold absolute pressure) sensor - low input (to computer)
P0108 MAP (manifold absolute pressure) sensor - high input (to computer)
P0122 TP (throttle position) sensor - low input (to computer)
P0123 TP (throttle position) sensor - high input (to computer)
P0171 fuel system lean
P0172 fuel system rich
P0201 fuel injector 1 control circuit malfunction
P0202 fuel injector 2 control circuit malfunction
P0203 fuel injector 3 control circuit malfunction
P0204 fuel injector 4 control circuit malfunction
P0300 multiple engine misfire detected
P0301 cylinder 1 misfire detected
P0302 cylinder 2 misfire detected
P0303 cylinder 3 misfire detected
P0304 cylinder 4 misfire detected
P0336 CPS (crankshaft position sensor) range/performance
P06xx control module (computer) failure


Possible bad parts:
TP (throttle position) sensor - Duralast TPS172 $51.99 at www.autozone.com

Fuel pressure regulator:
www.autozone.com/autozone/regairinfo/repairguide/repairGuideContent.jsp?pageId=0996b43f8036e816

Fuel Pump:
www.autozone.com/autozone/repairinfo/repairguide/repairGuideContect.jsp?pageId=0996b43f8036e7c7

Fuel Filter:
www.autozone.com/autozone/repairinfo/repairguide/repairGuideContent.jsp?pageId=0996b43f8036e787

Fuel rail (supply manifold) and fuel injectors:
www.autozone.com/autozone/repairinfo/repairguide/repairGuideContent.jsp?pageId=0996b43f8036e7a0

Could also be dying fuel pump relay - Duralast 19264 $14.99 at www.autozone.com.
I don't work for Autozone.com - just convenient info for some cars.

Autozone.com will expect you to register (free) to access their repair guide database (which has pictures - especially helpful for finding sensors).

Crank sensor!

very strange and rare problem. something is keping the injectors open instead of pulsing them. The command to ground the injectors comes from the PCM, Powertrain Control Module. It may be a good idea to pick up a used one from a salvage yard. car-part.com is a good place to look. You will need the info off your module to match up.
Do you have 2.0L SPI engine or 2.0L Zetec engine?
Look on the page with the * to find the lowest price part.
aso, check for shorted wire going to injectors
---------------------------------------------

Mechanical Returnless Fuel System The fuel system consists of a fuel tank with reservoir, fuel pump, fuel pressure regulator, fuel filter, fuel supply line, fuel rail, fuel rail pulse damper, fuel injectors, and schrader/pressure test point. Operation of the system is as follows (Figure 62):

1. The fuel delivery system is enabled during crank or running mode once the PCM receives a crankshaft position (CKP) sensor signal.

1. The fuel pump logic is defined in the fuel system control strategy and is executed by the PCM.

1. The PCM grounds the fuel pump relay, which provides VPWR to the fuel pump.

1. The inertia fuel shut-off (IFS) switch is used to de-energize the fuel delivery secondary circuit in the event of collision. The IFS switch is a safety device that should only be reset after a thorough inspection of the vehicle (following a collision).

1. A pressure test point valve (schrader valve) is located on the fuel rail. This is used to measure fuel injector supply pressure for diagnostic procedures and repairs. ON VEHICLES NOT EQUIPPED WITH A SCHRADER VALVE, USE ROTUNDA FUEL PRESSURE TEST KIT #134—R0087 OR EQUIVALENT.

1. Located on the fuel rail is a pulse damper. The pulse damper reduces fuel system noise caused by the pulsing of the fuel injectors. The vacuum port located on the damper is connected to manifold vacuum to avoid fuel spillage in the event the pulse damper diaphragm were to rupture (the pulse damper should not be confused with a fuel pressure regulator).

1. The fuel injector is a solenoid-operated valve that meters the fuel flow to each combustion cylinder. The fuel injector is opened and closed a constant number of times per crankshaft revolution. The amount of fuel is controlled by the length of time the fuel injector is held open. The injector is normally closed and is operated by 12 volt VPWR from the power relay. The ground signal is controlled by the PCM.

1. There are three filtering or screening devices in the fuel delivery system. The intake sock is a fine, nylon mesh screen mounted on the intake side of the fuel pump. There is a fuel filter screen located at the fuel rail side of the fuel injector. The fuel filter assembly is located between the fuel pump and the pressure test point/schrader valve.

1. The fuel pump (FP) module contains the fuel pump, fuel pressure regulator and the fuel sender assembly. The fuel pressure regulator is attached to the fuel pump in the fuel pump module located in the fuel tank. It regulates fuel pressure supplied to the fuel injectors. The fuel pressure regulator is a diaphragm-operated relief valve. Fuel pressure is established by a spring preload applied to the diaphragm. Excess fuel is bypassed through the regulator and returned to the fuel tank.
   
   
   
   Figure 62: Fuel System—Mechanical Returnless

Electronic Returnless Fuel System The fuel system consists of a fuel tank with reservoir, fuel pump, fuel rail pressure sensor, fuel filter, fuel supply line, engine fuel temperature sensor, fuel rail, fuel injectors, and schrader/pressure test point. Operation of the system is as follows (Figure 63) and (Figure 64):

1. The fuel delivery system is enabled during crank or running mode once the PCM receives a crankshaft position (CKP) sensor signal.

1. The fuel pump logic is defined in the fuel system control strategy and is executed by the PCM.

1. The PCM commands a duty cycle to the fuel pump driver module (FPDM).

1. The fuel pump driver module modulates the voltage to the fuel pump (FP) to achieve the proper fuel pressure. Voltage for the fuel pump is supplied by the power relay or FPDM power supply relay. (For additional information on FPDM operation, refer to PCM Outputs—Fuel Pump and PCM Inputs—FPM.)

1. The fuel rail pressure (FRP) sensor provides the PCM with the current fuel rail pressure. The PCM uses this information to vary the duty cycle output to the FPDM to compensate for varying loads.

1. The engine fuel temperature (EFT) sensor measures current fuel temperatures in the fuel rail. This information is used to vary the fuel pressure and avoid fuel system vaporization.

1. The fuel injector is a solenoid-operated valve that meters the fuel flow to each combustion cylinder. The fuel injector is opened and closed a constant number of times per crankshaft revolution. The amount of fuel is controlled by the length of time the fuel injector is held open. The injector is normally closed and is operated by 12 volt VPWR from the power relay. The ground signal is controlled by the PCM.

1. A pressure test point valve (schrader valve) is located on the fuel rail. This is used to measure fuel injector supply pressure for diagnostic procedures and repairs. ON VEHICLES NOT EQUIPPED WITH A SCHRADER VALVE, USE ROTUNDA FUEL PRESSURE TEST KIT #134—R0087 OR EQUIVALENT.

1. There are three filtering or screening devices in the fuel delivery system. The intake sock is a fine, nylon mesh screen mounted on the intake side of the fuel pump. There is a fuel filter screen located at the fuel rail side of the fuel injector. The fuel filter assembly is located between the fuel pump and the pressure test point/schrader valve.

1. The fuel pump (FP) module is a device that contains the fuel pump and the fuel sender assembly. The fuel pump is located inside the reservoir and supplies fuel through the fuel pump module manifold to the engine and the fuel pump module jet pump.

1. The inertia fuel shut-off (IFS) switch is used to de-energize the fuel delivery secondary circuit in the event of a collision. The IFS switch is a safety device that should only be reset after a thorough inspection of the vehicle (following a collision