I have a 1992 2 Door Cherokee, but the engine was swapped before I bought it. The engine is to an 02 Jeep Grand Cherokee. Both engines were inline 6, and both are 4.0L. I replaced the fuel pump but now that I think about it, the fuel pump is for a 92 Cherokee. Would that affect the way it runs? I ask because my Jeep idles very bad now. It didn't want to start about a week after the fuel pump was replaced so I changed the battery and fuel filter. It starts but runs off. It gargles and chokes and idles at 500rpms then shoots up to about 1500rpms and will continue doing this as long as I keep the Jeep running. If I give it gas sometimes it wants to catch and sometimes it'll continue choking. I took it down the street to see how far I could go, because it's parked in a place where there is a possibility it could become towed. I would go and maybe reach about 15 to 20mph then it'll gargle and choke really loud, kind of like an aggressive drag car. Any ideas? Help is greatly appreciated.

 

best thing to do is check the flow ratings on the 92 pump vs the 02. i dont see there being any difference, but you never know.

did the jeep run like this before the new pump?

 

Probably.

The 2002 4.0 needs 44-55 lbs. of pressure.
The 1992 4.0 needs 31-39 lbs. of pressure.

 

I'm sure only the block and cylinder head are from the newer vehicle, all of the other stuff like the intake manifold are from the 92. Check your fuel pressure.

 

As stated above it would have to have only been the longblock(I seriously doubt someone went to the trouble to swap the EFI system from a WJ).

In which case your only dealing with the 92 EFI system. Check for fuel pressure at the fuel rail test port, if off by more than a few PSI replace the pump.

Make sure to use a lubricant on the Oring for the pump sender seal to the fuel tank, failure to do so can result in a pinched oring that leaks fuel.

 

It was running like this before I changed the new pump. Then it continued to do the same thing about a week later.

 

How could I check the fuel pressure? I hear you could possibly rent a gauge but I'm not sure where exactly.

 

here is your problem. 80ish to 96 1/2 xjs all had Fuel Pressure Regulators on the fuel rail. after 96 they all went into the tank. Meaning there was only one fuel line running from the tank to the engine bay, i know because i had both model years and i spent enough time staring at them in the jy. your problem is most likely the FPR or vacuum(???). The entire fuel sending unit that sits in the two different types of gas tanks differ from one another.

I don't have a solution for you, but try getting your hands on the FPR for the year/model of the engine and see if it will fit on the fuel rail of your new rig. Let me know if it works or not.

 

sensors might be another biggie, obd 1 vs 2. eletrical grounds, timing? Wish i was there to see for myself.