Name the problem game....winner gets +10 internet credits

[loki_racer]

There's a guy on base that offered to sell me his 1998 Cherokee for $200. He said he took it to the auto skills shop and the mechanic there said he needs a new oil pump (I haven't been able to confirm why the mechanic said the oil pump was the issue.

The XJ has zero leaks.

I cranked it up and it idles very rough and tries to die. It has been sitting for months without a crank. Is the rough idle likely bad fuel? Or is it likely linked to oil sending unit and/or oil pump?

I've been reading on how to determine if it's the oil sending unit or oil pump that is the problem, but haven't been able to figure out an easy way to determine which is the problem.

If the oil pump went bad and the guy drove it, how painful would that be on the engine?

 

[UNCC_99XJ]

Can you get your hands on a mechanical gauge? If so I'd hook that up and let it idle (even if it is crappy) to see what pressure you're actually getting.

If the pump went out, it would depend really on how long he drove it. The top end especially would be in bad shape if he drove it for long enough.

 

[dave92cherokee]

I would lean towards bad gas being the culprit for the rough idle and not having run for months. When I got the manche back to a state it could be started it took a couple of cranks to get it fired up and then ran rough for a little bit till it started to warm up and it smoothed out. I'd start by draining the old gas and putting in fresh along with new fuel filter and plugs which should help the idle. If the oil pump actually went out (sounds like the typical low oil pressure reading on gauge problem) then it could be very bad if driven for any length of time. But for $200 I'd pick it up regardless as even parting it out it's worth more than that.

 

[superdave]

I would lean towards bad gas being the culprit for the rough idle and not having run for months. When I got the manche back to a state it could be started it took a couple of cranks to get it fired up and then ran rough for a little bit till it started to warm up and it smoothed out. I'd start by draining the old gas and putting in fresh along with new fuel filter and plugs which should help the idle. If the oil pump actually went out (sounds like the typical low oil pressure reading on gauge problem) then it could be very bad if driven for any length of time. But for $200 I'd pick it up regardless as even parting it out it's worth more than that.

I agree with this. Also, check the cat converter for clogs. If it's ever been off road in water you could have a bunch of crud in the cat. Buy it. You'll kick yourself if you don't. You can always get a junkyard engine for a few hundred $.

 

[loki_racer]

I'm in Italy, junk yards with Cherokees in them don't exist.

This thing has never been offroad a day in it's life.

Ya, I think I will buy it and if it runs with a couple hundred bucks of maintenance costs, I have a winner, if not, I will part what I can online and scrap the rest.

 

[jeepgeek2002]

check the wireing from distributor cap to plugs.. if the wires aren't setup right for the firing order it will idel really rough and die...
as for bad gas. pull the fuel pump out of back of the tank and place it in a bucket full of clean gas.. crank it and let it run ... should clean the lines too.. then you can suction the bad gas and dispose of it.

 

[loki_racer]

Aight. I'm pulling the trigger on this joker. My wife isn't sold on the idea of a second Cherokee in the stable, but I know the interwebs will support my purchasing decision.

I'll upload photos tomorrow. You clowns are going to die when you see this thing.

 

[xjtrailrider]

I've seen several 4.0 oil pump failures here lately. MAKE sure you have pressure with a mechanical gauge before you run it or your $200 deal will turn into a $1000 bad deal.

Then I'll buy it from you and drop one of my extra engines in it

 

[kf_chris]

One of my buddies in Sicily got bad gas in his Volvo, and I got it a few times in both the Maserati and on one of my bikes. They don't control that stuff so it could be a culprit. Dunno about the oil pump possibility. Good luck!

 

[J Pugh]

MAKE sure you have pressure with a mechanical gauge before you run it or your $200 deal will turn into a $1000 bad deal.

Maybe it's obvious to everyone, but I'm not reading anywhere that the gauge reads 0 oil press?

Anyway, I would just let it sit until you can get a new sending unit, since that's the likely culprit for no oil pressure on the gauge. When I was at Ramstein, I was constantly frustrated with the hobby shop's lack of real tools like this, so I think you will have a hard time locating a mechanical gauge. Just spend 35 bucks on a new sending unit, autozone ships to APO/FPO for free, at least they used to. Scenario 1: You fix the oil pressure problem; Scenario 2: You discover you have a bigger oil pressure problem. What's to lose?

As for the rough idle, jeez, I'm no help there, I'll probly stay tuned just to hear the answer. If it really hasn't been cranked except when you had it idle badly on you and try to die, well, I'd say something with the fuel is a likely suspect. GL.

cheers