Not that difficult, it will only take around 5 hours to complete the job (when i remember well). You are 100% possitive that the problem is the fuel pump and not a relay?
Lowered my tank some years ago to have a look at the pump, after some strange noises started to come from there. Before starting the job, remove the fuel pump relay from the power distribution center under the hood and start the engine, to relief all pressure from the fuel lines. After some seconds the engine will die. Now remove the negative battery cable, safety first.
In principle you have to disconnect all hoses behind the left rear wheel aft cover and remove the fill opening. Then remove the lines at the fuel filter/pressure regulator (also a good time to change this part, as it is fairly cheap and you have it disconnected now). Also disconnect the electrical connectors from fuel pump and fuel level indicator.
Then remove the skid plate below the tank. The tank itself is hold in place with 2 bands. The tank should be as empty as possible, otherwise it makes it more difficult to manouvre or control it. Put a jack below it with a large piece of wood to spread the weight or even better 2 jacks. I did it on my own, but the help of a buddy would make it all much easier. When the tank is lowered a bit, have a look if all lines and connectors are loose before breaking anything.
Now with the tank on the ground, remove the large plastic nut which keeps the fuel pump module in place. There is a rubber seal which should be changed (eventhough i didnīt do it, but you take a risk of leaks afterwards). Take care when removing the pump unit that also a float is a part of it, so take it out with a bit of care to not bend the float arm. You can change the complete fuel pump module (expensive), or only the pump refill. It takes a bit of fiddeling around to open up the fuel pump module, but its possible without breaking anything. There are 2 prefilters in this module, one mounted directly on the pump inlet inside the cannister (the small one) and the other larger one on the outside of the cannister. Would be good to change them both as well at this time.
In attached pictures you can see the pump module in pieces, second picture the complete pump module/float assy and the last picture shows the pump module in the tank. Take care to lign up the pointer on the pump module within the 3 stripes on the tank. In this way the float is free to move.
JEEP Grand Cherokee 4.7 Lmtd 2004
HID 8000K in low and fog / Quad Squad member
Monroe Reflex shocks /
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