Running rough 4.0

[1998Wrangler]

New to the Jeep life and this forum. I just bought a 98 wrangler automatic w/ 4.0. Replace starter flywheel TPC Crank sensor. It’ll run perfect for a few days and then acts like it’s running out of fuel we reply Dist cap too. Any chance you guys know what to check?
Jason

 

[Jerry Bransford]

Could be your fuel pump is starting to fail. Our fuel pump pumps have their share of problems, I'd start by checking the fuel pressure at the test port on the fuel rail where the injectors are. It should be very close to 49 psi.

If you end up replacing the entire fuel pump assembly (easiest), avoid store brands or cheap online store brands like Airtex or Spectre. If you're handy with tools I'd replace just the fuel pump itself with a Bosch who is the OEM. If you're not ready to get that deep into the fuel pump assembly, you can get the entire fuel pump assembly which includes the fuel pump, fuel pressure regulator, and fuel gauge sender. Bosch no longer makes the entire assembly, and many of those who still do have terrible quality and reliability.

https://www.rockauto.com/en/catalog...fuel+&+air,fuel+pump+&+housing+assembly,10147 (stay with the Daily Driver better quality models at the bottom of that page) has a good assortment to choose from, Delphi seems to be the one that some report good luck with since Bosch stopped making the entire assembly.

No guarantees it's the fuel pump but at least measure its pressure to see if it's the possible problem or not. Most auto parts stores will lend you a pressure tester for free. If it tests bad avoid the temptation to buy the fuel pump assembly through the store since store brands are seldom reliable for long.