ReyPerez337

Hi guys I'm in need of some help. I have a 1996 XJ with the 4.0 inline 6. Lately it's been having a bog when you try to give it gas. So for example it starts up fine idles Kind of ugh with a small mis firing sound. When I try to give it gas it bog down, back fires and loses power. so I would have to tap the gas over and over again untill it gets power again and the bog goes away. iv changed the fuel filter, and spark plugs already. Would like some help trying to figure this out.

Bustedback

Check the fuel pressure

tjwalker

Yup, that is absolutely the next step. Gotta get some data here.

96 was a mixed year. Early models had the system with the fuel pressure regulator under the hood. Later models have the whole shooting match internal to the fuel tank. Gotta know which you have to know the fuel pressure spec.

Early 96 XJs should see 31 psi at idle, 39 psi with the vacuum line to the fuel pressure regulator disconnected (be sure no raw fuel is in that vacuum line) and later mfg. 96 XJs need 49 psi at idle.

Fuel pressure gauges can be rented inexpensively from many parts stores; call around for availability.

ReyPerez337

Have not checked fuel pressure yet, but i did drop my gas tank, it was clean and fuel pump looked recently clean but who ever replaced it before me did not seal the fuel pump on all the way and gas was leaking out of the fuel pump cover. Would that cause lack of fuel pressure? Also I have ford injectors out of a crown vic that had missing caps on the end that goes into the intake not the fuel rail.... Any ideas guys? Last night it got worse it would die and not start, then 20 min later it would fire right up run and idle normal then 10 min down the road it starts bogging and losing power and just dies and its a back to back thing, including back firing and lots of engine vibration.

tjwalker

Usually not. I've seen leaking from the top of the fuel pump a few times and it hasn't affected fuel pressure.

Let testing lead the way. Test your fuel pressure. Don't guess. You can't tell a thing in that the fuel pump looked clean. That has no correlation with function.

ReyPerez337

I guess ill do that tomorrow then for sure. How about not having the 2nd o2 sensor in the rear? would that cause this problem as well? My check engine light is on.

Bustedback

Classic symptoms of a failing fuel pump. It may look clean on the outside, but it's what is inside the pump that matters. Check the fuel pressure with the key on engine off, start the engine and look at the pressure, drive around for a while with the gauge hooked up and keep an eye on it. I have a feeling you're going to drop the tank again.
Why is the down stream O2 not hooked up? It won't cause the problem you're having, but it will set a check engine light.

ReyPerez337

okay I'll do that tomorrow and my buddy who had it before me took it off since he ran a straight pipe that I'm fixing and giving it a new custom exhaust system.

Bustedback

Running without a catalytic converter is a no no.

ReyPerez337

I know I'll be putting a high flow cat on it

ReyPerez337

okay guys i checked my fuel pressure today and it was at 24psi at idle, and when i tried reving the motor it stayed at 24 and when i reved it at high rpms the pressure would drop a few then go back up to 24 at idle.

tjwalker

1996 was a year of change for the fuel system. Early systems (with the fuel pressure regulator under the hood) had a fuel pressure spec. of 31 psi at idle. Later model 1996 XJs had a spec of 49 psi at idle

But with your pressure at 24 at idle, you would be out of spec, no matter which system you have.

I'd say it's time for a new fuel pressure assembly. Do NOT buy Airtex. They are offered by many parts stores as a low price point option. They have a reliability issue IMHO. I will not install one nor will I recommend them. Bosch is my favorite. Carter is my second favorite.

Good luck and keep us updated!

Bustedback

You'll get really good at replacing fuel pumps if you install an Airtex pump. Go with Carter or Bosch.

ReyPerez337

Okayyyy thennn well i will not buy airtex then lol hahah

ReyPerez337

Well guys i checked the fuel pressure and it was at 24psi, I then changed the fuel pump and it fixed my problem! Thanks guys for all the help! The XJ is back up and running like a champ.