Originally Posted by 96 XJ WIP

Ok here it is i have given up after days of searching and testing here is what i have going on...
96 xj 4.0L I had a check engine light on for forever, finally got around to giving her a tune up (she had been sitting basically for the better part of the year) Plugs, wires, air, oil, radiator flush, injector cleaner in the tank, O2 sensors, and a thermostat which led to my first issue there was no gasket in the thermostat box got to the point to putting her all back together at about 1am half way in and half way out of my garage at the apartment i live at waited until 4am took a chance left it in the fire lane got back out there at 730am to check in before the parts store opened and she was gone, towed ... weaksauce ... got her back 2 days later had to put the thermostat on and fill up with coolant right there in the tow yard (lol good story for the grandkids) she fired right up and off i went ran good, still had one problem that had been preexisting remaining...when i put my foot on the floor she bogged down almost as though she wasnt getting enough fuel or maybe too much (this only happened when i was in gear driving and floored it, picture getting on the freeway and accelerating to speed in 3rd i could only use about 7/8 of my gas pedal) cleared the codes went to fire her back up and she ran like ****. Let it run for a minute like crap just to see if the memory caught back up never did so i killed her, i proceeded to wait for about 5 minutes for the thing to start back up had to really milk the throttle home, toe heel type driving always had to have the gas down a bit. waited a couple days started her up and still not running right new CEL checked the codes said i was running lean (i dont remember the number) drove her home and she died, i had noticed an exhaust leak in the back of the engine compartment before she died, this led me to some kind of vacuum issue. I have since replaced the intake/exhaust manifold gasket, cleaned the throttle body, cleaned injectors and replaced o rings, motor mounts (i was already there), checked the vacuum lines (to the best of my ability im not sold i have a vacuum leak elsewhere just thought the blown gasket could be the cause). So here is where i am today...When i turn the key i hear the fuel pump but im not reading any pressure or getting any gas on my hand at the fuel rail when i release the pressure. She will crank and be RIGHT on the verge of starting if i shoot some throttle body cleaner into the throttle body directly she will fire and as long as i keep adding it in i can rev the engine out but once i stop even if i am playing with the throttle she dies. What else should i be testing/checking. The fuel pump and the CPS are both less than 4 years old (though both are aftermarket from NAPA)

All help is appreciated, i am pretty handy with a wrench just not with anything diagnostic apparently

Originally Posted by Boliaris

i have a dana 35 3.73 front and had a 3.73 in the rear but some very smart guy put a 3.55 in place of the 3.73 is that what is causing my 4 wheel drive to be very rough or could it be that i changed my speedo gear setting( its a 29 tooth count but was set on 34-39 so i changed it to 24-31 with 32s) could that be my problem

Originally Posted by Boliaris

i have a dana 35 3.73 front and had a 3.73 in the rear but some very smart guy put a 3.55 in place of the 3.73 is that what is causing my 4 wheel drive to be very rough or could it be that i changed my speedo gear setting( its a 29 tooth count but was set on 34-39 so i changed it to 24-31 with 32s) could that be my problem

Originally Posted by Boliaris

i have a dana 35 3.73 front and had a 3.73 in the rear but some very smart guy put a 3.55 in place of the 3.73 is that what is causing my 4 wheel drive to be very rough or could it be that i changed my speedo gear setting( its a 29 tooth count but was set on 34-39 so i changed it to 24-31 with 32s) could that be my problem

Originally Posted by lowrange2

The first thing I'd do is verify that the gears match.

You either have a Chrysler 8.25 of Dana 35 in the back and you most certainly have a Dana 30 up front.

I'd pull the cover on the front and verify the gear ratio.

I can't imagine anyone would have wasted the effort to gear to 3.73 from 3.55.

Originally Posted by 94XjSport94

It's a 5 speed, so factory with the 6cyl would have been 3.07.

Pull the cover and count the teeth in both axles.

Originally Posted by lowrange2

You most certainly have a Dana 30 up front.

Originally Posted by lowrange2

Still, 3.07 to 3.73. Seems like a waste to me.

Originally Posted by NewKindOfClown

3.73s were used factory in some Tow Package equipped automatics, and also in older Up Country models. I've only seen one in person.