When my car runs for a while it feels like i loose all my gas pressure and when i hit the gas it wont go

First of all, the new fuel pump may be bad. disconnect line at fuel filter where it goes through filter. and see if fuel flows, or have someone to put hand flat on bottom of tank and try to start car. if fuel pump is working you will feel a vibration on tank. if it does not work, check the fuel pump fuse in fuse box before you exchange it.and or the fuel pump relay! when car is running it runs constantly, when you simply turn key to on position, it runs for about 3 seconds(until fuel pressure in line comes up. and then cycles off.

run fault code and look at injector problems . have a fuel pressure test done to check pump--pressure regulator--filter

2 possible reasons 1 check ignition timing and adjust. 2 check for crossed plug leads on 2 cylinders --firing order.

check the pump pressure,what year

your fuel pump is in the gas tank in the rear of the truck. It sounds like it could be a loose connection on the fuel pump sending unit. That's ware I would start looking at first. If that's not it you need to have pressure test done on the fuel pump. If you are having trouble starting the truck every now and then, this a good sign your fuel pump is starting to go out. Good luck!

Auto or manual transmission?

Hi!!It sounds like your fuel pump is not working. Check fuel pump relay on engine compartment fuse box have somebody to turn the ignition key to the RUN position, DO NOT CRANK ENGINE (feel if the relay clicks when the key is turned, it will only be energized for a couple of seconds and then you should feel when it gets de-energized. if relay is OK, remove the fuel tank gas cap and repeat the same key operation, listen to the fuel pump coming in, again this will be running only for a couple of seconds, try a few times until you are sure one way or the other. If fuel pump works, then replace fuel filter and try to start vehicle. If vehicle does not start. You need to check fuel pump pressure. borrow a tester form Autozone or similar auto parts store. The fuel pressure should be between 30-40 psi with key ON engine OFF. If pressure is off either way, replace fuel pump. Here is how to hook up the fuel pressure tester
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Check the fuel pressure. Even if it's running it may not be producing pressure. See if you can keep it running on starting fluid or carbuerator cleaner. If so replace the pump.

Is the gas tank above 1/2 tank now?

A worn / aged fuel pump will fail when it's hot and the fuel level is low (example: below 1/4)

Park your car in a cool area.

Start the car when it's cold outside,

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Check the engine fuel pump pressure.
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Replace the fuel pump relay,fuel filter,fuel pump and fuel pump stainer at the same time.
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it feels like you have a transmission pump problem which is common with chrysler front wheel drive(caravan).when fluid warms up it probably looses pressure. I recommend to get a pressure check when hot.