2004 3.9 having starting problems. There is no shrader valve where do you hook up the guage? Does anyone have the dimensions to cut the trunk out for fuel pump swap?

 

You do not hook up a gauge. Unless you want to add a splice somewhere to add one. You would instead get a scan tool/code reader that can get that information from the computer, real time data read. You'd want to see 35-70 PSI on the fuel. The computer will know.

As far as pump running, you want to ensure 12V at the fuel pump connector, which is located just behind the rear bumper at the tank. You'll need to look up the pinout of the connector to get that. If there's no 12V there on the proper connectors, with key on, there's your problem. You have a wiring issue. Either fuse, computer, inertia switch, relay, CCRM, wiring... something's not getting the power there. That'll involve a large amount of tracework, but totally doable.

If you have 12V at the tank, then listen for the pump. You should definitely hear it run briefly as a fairly noticeable hum when you turn the key on. If you don't, then the pump is likely bad. You can also use that same pinout on the pump side connector and 'direct inject' 12V into the pump and see if it runs at all. If it doesn't, well, dropping the tank is in order as you need a fuel pump.

And no, you do not cut the trunk. Drop the tank. Cutting the trunk is a good way to mess up the car and/or the tank. I know people do it, but seriously... just don't. Please.

And as an aside... fuel filter good? Perhaps it's not...

I hope that helps. And welcome to the forums!