4.0 Running issues

[JT_Law]

Ok all you tech gurus, time to shoot from the hip and hopefully point me in the right direction

1990 Cherokee
175k
is lifted and yes I wheel it, but....

About a year ago it developed a singing in tank fuel pump, (on wheeling trips this can be heard up to 30' from the Jeep), unsure if related to what started about 3 weeks ago.

Until tonight when it did it while only about 1/2 warmed up it has only been when it is up to temp.

Will be driving along and it will start acting like it is running on 2 cyl, or maybe only running because am going over 35 (auto trans)

If I give it some gas it will stumble along, then I get one or two sounds like an internal backfire and it will roar back to life.

Also, has taken to just dying while at a light, no stutter or any warning, just POOF dies, pop it in neutral and it fires right back up just fine (has also done this before if I slam the hatch to latch it)

Plugs are reasonably fresh (haven't checked em personally, but only a few k miles on em).

Could be some vacuum issues, I know some of the lines, like one on back of airbox are so old, stiff, and hard that it is more or less just kind of sitting there loose

Only fuel ran in last 12 years was mid grade, switched to super at the coast last weekend and thought it was solved (octane), but new tank of super in town and it is back to doing it.


Any idea on where I should start digging into it?

Much obliged
Ron

 

[Lonestar]

I had a problem like this a couple of years ago. Turned out that screws that hold the sensor ring for the hall effect sensor to the distributor shaft had fallen out, causing the ignition to not fire consistantly. Might be worth pulling the distributer cap off and check.

If its not that, then check for a lack of fuel. Change the fuel filter to see if it is plugged (also a good idea if you haven't changed it in the last year). Check the fuel pressure, should be around 40 psi. If its low it is either the pump or the pressure regulator.

 

[Pioneer84]

You said the fuel pump inside the tank is making a lot of noise it may be a sign its going bad you should only hear it just at start up. If its going bad it could send incorrect or low fuel pressure to the engine.

 

[Dr. Dyno]

You said the fuel pump inside the tank is making a lot of noise it may be a sign its going bad you should only hear it just at start up. If its going bad it could send incorrect or low fuel pressure to the engine.

x2. I think all the stumbling/dying issues together with the abnormally noisy fuel pump are signs that the pump is on its way out.

 

[JT_Law]

Drat, ya'll weren't supposed to confirm my first hunch

Twas trully hoping for something not requiring removal of the gas tank, lol.

Thanks much!

Ron

 

[Pioneer84]

If its like my 87 you don't have to remove the gas tank. look at the upper side of the gas tank facing the front of the jeep you should see a large Ring its held on with a locking ring the fuel pump is just behind it.

 

[langer1]

Drat, ya'll weren't supposed to confirm my first hunch

Twas trully hoping for something not requiring removal of the gas tank, lol.

Thanks much!

Ron

It don't require removal of the tank.

 

[Lonestar]

Make sure its not more than half way full or you will have a nice surprise when you pop that ring off. BTW when I did mine I loosened the tank straps a little to drop the tank a couple of inches. It made things a little easier I thought.

 

[JT_Law]

YAHOOOOOOO!:cheers: