I was looking for a Cherokee for my daughter to drive locally over the summer. finally found that was very close and seemed to be the right price. It's 98 Chili Pepper Red that has only had 1 owner. Very solid with 1 problem and I got it for $800. The 1 problem is that the engine won't run right. The previous owner said it was being drive on the highway and just quit. They hd it towed back to his house and he kept trying to get it started. He cut off the exhaust after the cat and said he got it to run but after a few minutes it would backfire and stall.
I already have a '99 that I have been through front to back. Did an in place rebuild to fix a cracked piston skirt on that one so pretty familiar with going through an engine. Have also changed the timing gears/chain in this one too so know how to do that.
Back to the '98. First step was doing a compression check. Cylinder 1 was ~110. Not a bad start considering it hasn't run in awhile and the battery is pretty weak. Cylinder 2:0, cylinder 3:0, cylinder 4:0. I go back and check cylinder 1 to make sure my gauge is still working. Get 110 on 1 again. Cylinder 5: 110, Cylinder 6: 110
Finally tally:
1:110
2:0
3:0
4:0
5:110
6:110

I don't see any oil in the coolant overflow and I don't see foaming on the oil dipstick. Next step will be to drain the oil and coolant to see what those look like.

I was surprised by the 0 values. Does this seem like a head gasket problem, valve timing problem or cracked head problem?

I don't hear any clanging around from the timing chain so I doubt it's a jumped chain.

this is what I was thinking for next steps:
drain oil for a look
drain coolant for a look
get a leak down tester and try that (hoping I can rent one)
remove timing chain cover and look at valve timing
remove head and start looking at valves

I'm just a little puzzled by 3 cylinders having 0 compression.

Would appreciate any thoughts anyone has on this.

 

If it only has to run over the summer don't even bother with any diagnosis, drop a junk yard (97-99) engine in it & go.

 

Not quite there yet. I did take the valve cover off and turned the engine over by hand. didn't see anything obvious. I did not see signs of coolant in the oil.

 

Get an endoscopic camera attachment for your cell phone off Amazon. Or buy a borescope camera from Harbor Freight or Sears. Be sure to get one with LEDs on the end so you can see in dark spaces. Remove plugs, stick camera inside, look for damage.

This method has the advantage that you'll also be set up to check your own polyps.

 

I would suggest doing a cylinder leak down test. Listen for the air leaking out, that will point you towards the correct diagnosis. For example, air rushing through the intake = leaking intake valve, tail pipe = exhaust valve; air rushing into the crankcase = piston issue (broken ring, scored cyl wall, busted piston); air coming out thru the cooling system = block/head/gasket failure. good luck.

 

I was thinking the same thing on a leak down test.
After thinking about it more, my bet is on blown head gasket.
Will most likely end up pulling the head to take a look at everything anyway. I have a good machine shop close by where I can get the head checked and fixed if needed.

Definitely want to replace the motor mounts while I'm in there and most likely the exhaust manifold is cracked etc. etc.

that's a ll so much easier when everything is torn down.

 

At least add a little oil to those cylinders and recheck compression. That might give you a little better of an idea.

 

Somebody baked it and maybe was not truthful about that. 98 block, and even head may be fine. While the shop is checking the head and fitting valves, inspect the bores for scoring or any sign if evil. (turn the crank via crank pulley, 7/8 maybe) I didn't notice that you posted the mileage on it.

Hard to kill a 4.0.....

 

The (brother or sister in law) of the PO said it cut out on the highway. They had it towed home. I don't the owner was being untruthful. He really just wanted it to go to someone who was going to fix it and keep it on the road since it had been in the family since new.
I did recheck the compression in the 0 cylinders after adding some oil and they were all 0 still.
Going to drain the oil and coolant tomorrow and go from there. Assuming those look ok, then I'll start taking the manifolds off and hopefully get the head all the way off to see if it is the head gasket. It has a recent VA inspection and was on the road until this happened. My biggest concern now is if it did overheat which blew the head gasket. Luckily, it wasn't driven anymore after this happened.

 

Three cylinders with absolute zero?

I'm not an expert in this department but I would guess something happened that screwed the cam up. Timing chain loose and jump a few teeth?

The odds of a head gasket blowing out on THREE cylinders is rather high I would think!

 

Stop fighting the inevitable. Pull the head.

 

Agreed.

 

I figured I knew what had happened when I pulled the lower radiator hose to drain the coolant. There was no coolant! Pulled he head today since I knew it was coming off anyway. Some interesting damage to the piston tops and rings. Some scoring on #2 cylinder wall but the others look fine. On #2 the little bits of piston ring fused to the piston top. The damage was pretty evident at the piston top on #2 and #4, but not on #3. Once I pull the pistons tomorrow, I'm sure the rings will show damage.
Turned the head over and put some gas into the valve side. Looks like some damage to the valve or seat on #2 (no surprise there), but the other looks ok. Will have to look further in the morning. Going to pull the pan and remove the pistons tomorrow to help decide on next step.

 

Wow

 

Yup. The PO was either very stupid (sounds like it) or he flat out lied to you.