89 jeep Cherokee drivability problem?

  • Thread starter Thread starter atrus96
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atrus96

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i have an 89 jeep cherokee 2 door. the guy i bought it from said that he had the 4.0 H.O. from a 95 wrangler put in it, i tend to believe him for how it runs. now i start it up and it drives fine but after an hour or so when accelerating it pulls fine to about 3 grand then falls on its face and wont go over 3 grand. i have to play with the throttle to even get it up to 45 and it take 2 or 3 minutes. i think it's the fuel pump but does anyone eles know what to check before i go run out and buy a fuel pump? it's hard to test as the problem only happens after an hour or more of driving and when i pull it back into the yard it's 3 or 4 am (i deliver newspapers with it). i replaced the fuel filter already
it will start up just fine after the problem occurs as far as i know, it has only happened twice, tuesday it started and i changed the filter, ran fine all wenesday morning and then thursday it did it again, it's not pulling a vacum in the tank as i thought there may have been water in the fuel so i filled it up on Tuesday when it did it the first time and it made no difference. when the problem occurs i can pull over and put it in neutral or park and it revs just fine all the way to redline so the problem is only there with a load on the engine
i highly doubt ignition or spark lose through wires as it does not happen all the time as spark problems normally do. this is very intermittent and almost seems like the in tank filter maybe pulling crap from the bottom of the tank and getting clogged. just a very weird problem, my friend is coming with a fuel pressure gauge soon we will see what that reveals
 
If it takes an hour to start dumping on you I'll bet you're pulling a vacuum on the gas tank. Try checking the vent lines or do a test run with a loose or vented gas cap. You could also pull over once it starts acting up and see if there's suction when you open the filler cap.

Does it run fine after shutting it off and restarting or does it need to cool down before it runs okay? Here's another thing to check: Overheating computer from being badly mounted,

I seriously doubt it's the pump. Usually they fail and stay that way.
 
Sounds like an ignition problem to me. Check plugs and run your hand over the plug wires while the engine is running and see if you get shocked. Replace the distributor cap and check/replace the distributor components.

Additional:
Check/replace the PCV valve if you are not getting vacuum.
 
you can buy a fuel pressure gauge at auto zone that will screw on the fuel rail.you can test the pressure to make sure you really need a pump.
 
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