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Jeep cherokee running bad when it gets to half a tank of gas

about 2 years ago, my 99 cherokee would start acting up at about 1/4 of a tank of gas…i would hit the throttle and it would lose all power like it wasn’t getting any gas, it wouldn’t stall out, but as soon as i would let off the throttle it would go back to running normal… i filled the tank and it ran fine again… i don’t drive it much i’ve only put maybe 3000 miles on it since then, and now it’s doing the same thing at half a tank now… it even stalled out a couple times while idling… do i need a fuel pump? a coil maybe? it usually runs great in the mornings when it’s cold… but when it gets hot out in the afternoon it starts doing it, or if its been running for a while… if that helps any… any help would be great before i start buying parts i don’t need… thanks in advance

You need to do some diagnosis while the vehicle is acting up.
I would check your fuel pressure when its acting up. I’ve run into a few vehicles that actually run while the tank is full just because the pressure and weight of the fuel itself was enough to get it to a running pressure. I would also check your electrical and computer. More common than not, when a computer gets hot it will not operate correctly.

The check engine light isn’t on, right? If you can reproduce it, ask a mechanic to put a gauge on the rail fuel pressure, it may be dropping for some reason. If you wanted to try something yourself, you could get all the pending codes read from the ecm. And you could see if the problem is for the better or worse when the gas cap is temporarily loosened. There might be an evap problem.

i also forgot to say that if you cold start it, let it run for a few seconds, then turn it off, then try to start it again… it starts hard… i either have to turn the key, a couple times to let the fuel pressure build up… or put the pedal all the way down while turning it over… i hope its not a computer… it’s weird too, that the check engine light didn’t come on when it was doing it…

I think you’re looking at a fuel issue like George said, your gas cap might not be sealing and you could be looking at an EVAP issue. I know that on those Cherokees, they have an EVAP system that comes from the tank to the intake manifold.

When an engine gets warmed up and has issues running, it can point toward fuel pressure loss. At initial start up the computer dumps lots of fuel into the engine to get it to operating temp quicker. When the vehicle warms up, the computer retards the amount of fuel and RPM’s the engine will get. I would definitely check fuel pressure and test the EVAP system if at all possible. You could even run some fuel treatment through the system as an extra measure.

This is based off of the notion that no codes are being thrown. There is a gas cap and EVAP sensor on that tank and if there are any issues it should throw a code. (Doesn’t mean it will though).

have you changed the fuel filter?

well that gives me a better idea of what it could be… i was seriously about to buy a gas pump… is the EVAP system something simple to fix? or is it something that a mechanic would have to deal with?

no i havnt…i think the fuel filter is inside the pump

it not on mine. its easy to get to under neath. but your s is newer soIDK. I d try that first tho. its the easiest usually, and cheapest

That’s the indication of a weak fuel pump.

When the gas tank is full, the level of the gas in the gas tank creates what’s called head pressure. This is the effect of gravity on a column of liquid. This head pressure can assist a weak fuel pump.

Then as the level of gas in the gas tank decreases the head pressure decreases. The head pressure decreases to a point where it no longer assists the weak fuel pump. So the engine lies down and has no power.

Get the fuel pressure tested when the engine displays this problem.


It could be a weak fuel pump but there could be another problem that’s easy to check. My wife and I have both owned Jeep Cherokees from the time they were introduced until the last one made around 2002. The fuel cap may be getting clogged and a vacuum may be developing in the fuel tank. I’ve had this problem before a few times and the fix was to loosen the gas cap and leave it that way until a new one is installed. My wife’s Jeep Cherokee even pulled in the sides of the gas tank and the gas cap was extremely hard to loosen.