Fuel pump kicks on but not getting fuel to fuel rail

Not likely. It is also not likely that the regulator is in the fuel pump assembly. Some people mistake the check valve in the pump as a regulator. Also, some vehicles have a pump module which includes the fuel gauge sensor and that can be mistaken as the regulator by some DIYers. The caravan uses a return-loop fuel system. This means that the pump is cycling fuel from the tank to the fuel rail on one line and the fuel that is not needed at the injectors flows back through another line to the fuel tank. This is done to prevent the pump from building up too much pressure and allows the fuel flowing through the pump to keep it cool. Because of the looping system, there needs to be a flow restrictor (aka regulator) at the fuel rail to provide a constant pressure source for the injectors. The regulator is normally at the end of the rail and will have a vacuum line attached. Pull the vacuum line, place a rag at the vacuum port, and crank the engine. There should be no fuel coming out the port. If any fuel comes out of the vacuum port, the regulator is faulty. The regulator could still be faulty even if there is no fuel from the port, but fuel leakage is an easy way to be sure. If the regulator is not providing proper restriction to maintain pressure, then the fuel simply flows in a circular loop from and back to the fuel tank without enough pressure to allow the injector to do their thing,

You can't know the correct pressure. But you can get a good idea by removing the return hose from the fuel rail , fit a length of hose to the rail and into a container start the engine, and fuel will flow into the container if the regulator and pump are ok.

More likely the pump is not putting gas up to the engine's fuel rail.
With key on, not start, the pump should turn on for 2 seconds to put pressure in the line and fuel rail. Do you hear the buzz or hum from the tank with key on?
Did you put a fuel pressure gauge on the fuel rail's test port (shraeder valve), and find no pressure with key on? If so, you will need to check into the pump operation (assuming the fuel filter is not clogged). A quick test is to pull off the gas tank electrical connector, find the fuel pump wire in the connector, and use a test light grounded to a metal frame or a voltmeter. Check for power on the fuel pump wire, while the engine is being cranked over. If power then, your new pump is not working. It could be the ground for the pump, so you need to check that. If no power to pump, engine cranking, then you will have to find the fuel pump relay under the hood, and check the wiring to it. There is also a fuel pump fuse-it may be under hood or in the instrument fuse panel-need to find and check it.
If the pump is working and the fuel filter is clean, you should have gas in the fuel rail (which supplies the injectors with fuel under pressure). I have not heard of a pressure regulator problem that could cause no pressure, but then...
Post back what you find, or with comments. Hope this has helped a little.

If the pump kicks on, then it should be getting to the rail.
Sounds like an immobilizer issue (Not powering the injectors).
Disconnect a hose from the fuel rail inlet point (put it into a bottle or tub) and check if fuel is pumping during cranking.
If you get fuel at the rail, check immobilizer or ECU.

Check the fuel pressure regulator at the fuel rail or throttle body.

Keep in mind that you have several components there:
- Fuel Pump Sender Assembly,
- Fuel Pressure Regulator,
- Fuel Rail Assembly, and
- Fuel Injectors.

1.- Fuel Pump (Sender Assembly) - TESTING
Refer to the accompanying charts for fuel pump diagnosis and testing.

The fuel injection system remains under pressure, even after the engine has been turned OFF. The fuel system pressure must be relieved before disconnecting any fuel lines. Failure to do so may result in fire and/or personal injury.



Fig. 3.1L engine OBD system check to be done before fuel pump relay circuit diagnosis




Fig. 3.1L engine fuel pump relay circuit diagnosis (1 of 2)




Fig. 3.1L engine fuel pump relay circuit diagnosis (2 of 2)




Fig. View of the fuel pressure test port (Schrader valve)-3.1L engine

A - 3.1L engine fuel system pressure test (1 of 4)
B - 3.1L engine fuel system pressure test (2 of 4)
C - 3.1L engine fuel system pressure test (3 of 4)
D - 3.1L engine fuel system pressure test (4 of 4)



Fig. The fuel pump/fuel sender module assembly is mounted in the fuel tank


2.- Fuel Pressure Regulator - REMOVAL & INSTALLATION

(the fuel pressure regulator, which is located on the fuel rail assembly)

NOTE: Before removing the fuel regulator assembly, place a clean shop towel under the regulator to catch any fuel drips

1. Properly relieve the fuel system pressure.
2. If not done already, disconnect the negative battery cable.
3. On the 3.1L engine, remove the intake manifold plenum, as outlined in .
4. On the 2.4L engine, remove the fuel rail. Refer to procedure earlier in this section.
5. Detach the vacuum line from the regulator.
6. Place a shop towel under the regulator to catch any fuel that may drip out. Unfasten the fuel pressure regulator retaining screw, then remove the regulator by twisting and pulling it from the fuel rail.
7. Remove and discard the O-ring seal. Inspect the filter screen for contamination and replace if necessary.
   

To install:

1. Prior to assembling the pressure regulator to the fuel rail, lubricate the new rail-to-regulator O-ring seal with clean engine oil.
2. Place the O-ring on the pressure regulator and install the pressure regulator to the fuel rail.
3. Install the retainer or coat the regulator mounting screws with an approved thread locking compound and secure the pressure regulator in place. Tighten the mounting screw to 76 inch lbs. (8.5 Nm).
4. If removed, install the fuel rail assembly to the engine.

WARNING The fuel return pipe must be connected before tightening the regulator retaining screw to prevent the regulator from rotating. Rotation of the regulator could damage the retainer and spacer bracket and lead to a fuel leak at the regulator inlet.

1. Connect the fuel feed line and return line to the fuel rail assembly, use a backup wrench on the fittings to prevent turning.
2. Attach the vacuum line to the regulator.
3. On the 3.1L engine, install the intake manifold plenum.
4. Connect the negative battery cable. Turn the ignition to the ON position for two seconds, then turn it to the OFF position for ten seconds. Turn again to the ON position and check for fuel leaks.

continue...

Did you actually verify the fuel pressure at the fuel rail? If so, there are some other things to check, fuel filter, fuel rail pressure regulator and an obstructed fuel line.

fuel pressure regulator is what is in between the pump and the rails. it sounds like your regulator is restricting fuel flow

Sounds like the fuel pressure regulator. Check to be sure your fuel pump is pumping gas up to the fuel rails. You can usually hear the fuel pump kick on at the gas cap. I would change the fuel filter while you're at it. Just to be sure there's no trash caught within the filter.

try hooking up a fuel pressure test gauge to fuel rail pre filter and post filter and rev truck to 2500 rpm what is fuel pressure ?
next using a vacume pump attach to fuel pressure regulator pump up while engine is running only pump up to 8 psi to see if pressure changes if not replace pressure regulator .
it could also be ur speed sensor switch on overdrive transmission
good luck with it