The fuel pressure regulator is rarely the sole cause of that problem, its main job is to relieve excessive fuel pressure. I've replaced just the FPR a couple times to try to fix that problem years ago but only replacing the actual fuel pump ever truly fixed it. There's a check valve inside that fails which allows fuel that is supposed to remain up at the top of the engine for fast starts to instead drain back down into the fuel tank. The slow start is how long it takes the pump to get fuel back up to the engine.
I would buy the entire fuel pump/FPR assembly as a unit and make sure to avoid the cheap crap made by companies like Spectra, Airtex, or any of the store brands like are sold by Autozone. This is a PITA job to do so you don't want to have to redo. A Spectra I installed years ago lasted me all of 13 months, one month past its warranty.
The ONLY brand of fuel pump I'll recommend is Bosch which is also who is the OEM for the factory fuel pump. My Jeep can sit two months without being started but it'll start up instantly every time since installing the Bosch 3-4 years ago. Amazon.com is a great source for the Bosch fuel pump, just make sure to check the p/n that it is correct for your model year.
Last hint... to reduce the time it takes to crank the engine before it starts, cycle the ignition switch on-off-on 6-8 times before turning the switch to start. That'll give the fuel pump more time to get fuel back up to the engine.
These two photos show when I replaced just the FPR... it didn't fix the problem. The fuel pump is below inside the gas tank and is what the FPR is inserted into.
But if your TJ is a 2005 or 2006, they are integrated into just one module so they are not replaceable separately.
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