bada$$91xj

Alright guys its a 94 xj with the 4.0 i replaced a rusted out fuel tank with a new tank,pump,sending unit and filter. When i start it the jeep idles normal but when i go to apply gas slowly it wants to stall, hesitate, or buck. The weird part is if i stomp on it the jeep feels fine. I've tried switching the old fuel pump back over to and the same symptoms also filter was installed correctly arrow towards engine no gas leaks or vacumn leaks. This is my 6th jeep 3mjs and 3 xjs so i know its not a cps could a cracked exhaust manifold where they come together cause this thanks in advance tony.

aa7kn

I had the same problem with my XJ. even I put in a new fuel pump motor in the tank, it still did the same as your jeep is doing. I had to go thru 3 pumps before I finally got one that worked. you don't need to pull the tank to change it, the pump assembly is held in with a ring , you can reach it from under the car. also put a pressure gage on the fuel rail shradder valve, it should be around 40psi. but ill bet you have a defective fuel pump...good luck and make sure to let us know.

bada$$91xj

i know its not the fuel pump cause i tried putting the old one back in which was working and still was acting up, also did the pressure gauge and readings were anout 43 psi and leakdown over 30 minutes was only about 8-10 psi.

bada$$91xj

come on guys throw some more ideas at me please i'm a little stumped on this.

gat

To fuel out the fuel pump, then you measure the pressure at the fuel rail. What is the pressure at the rail? You can "rent" a huge from a parts store for free.
I would think that a problem at idle, but not a problem with the air intake valve wide open could be a problem with the air intake valve. Ensure that it is clean with carburetor/air intake cleaning spray.
Did you replace the fuel filter, air filter, spark plugs, spark plug wires, distributor cap, and distributor rotor? That'd be a complete change of the hard disposables since it seems like this is a new car to you.
--- sorry, I had skipped your reply with readings. No need to post the same reply twice for pressure readings.