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1998 Jeep Cherokee Tune-Up - Reviving a Dead Indian

Posted in How To: Engine on April 1, 2015
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This story began about 104 years ago. Well, OK, maybe not quite that long ago. This story actually begins about two years ago. Trasborg was working on another couple of Jeeps, and his ’98 Cherokee ended up sitting in his yard while he worked on and drove the other Jeeps. Then, the Cherokee needed to go to a show, and when he went to start it, nothing.

No big deal—jump it and drive it, right? Once we put on the jumper cables, it would crank but still not start. It sounded like it wanted to start with a few backfires through the intake or exhaust, but it never did actually fire. That was really weird because it was acting like the timing was off. However, the distributor is in a fixed location, and there was no way it could jump a timing gear tooth sitting there shut off in the yard for months. Even if it could, it should be backfiring the same every time. So, we decided it must be an electrical issue. Sitting in a yard for five months on dirt could let a lot of moisture come up from the ground under the hood.

The Jeep had 258,000 miles on it at the time and in all the miles we put on it, we never replaced the distributor, so we decided to start there. We popped the cap, pulled the rotor, and found the distributor filled with oil to the cam sensor location. Last time we checked, we were pretty sure that a distributor shouldn’t have oil in it. We knew the sensor didn’t need oil. So, we started looking for a sensor and distributor.

We found out really fast that, locally, the parts would cost us around $300. The problem was, while the distributor was obviously worn, it ran when we parked it. So, we didn’t want to blow all that money for what basically amounted to an oil seal. We found a new distributor at Rock Auto (with the sensor) and a new cap and rotor for $60. Sold! We dropped the new distributor in, and it didn’t even backfire. Hmm. We put the old one back in, and it started backfiring again.

After discussing the entire drawn-out and failed diagnosis process, Jeeps R Us decided to double check that we had the distributor in correctly before removing or swapping anything else. So, with a long prybar on the bolt in the harmonic balancer, the engine was turned over to top dead center.

Long story short, we tested the sensors with inconclusive results; the numbers were dead-on with some and erratic with others. So, we took another Jeep we had sitting there that was running, and just for grins, we swapped sensors back and forth. No change. At that point, the only electrical thing that made the engine run we hadn’t swapped was the coil. We were running a DUI coil and never had problems with it in the past, but nevertheless, we had the old coil from this Jeep on the shelf, so we swapped coils too and still no improvement.

We got to thinking that maybe some combination of worn electrical components combined with worn engine mechanicals allowed the Jeep to keep running. While we didn’t really think that could be it, we started checking mechanicals. We checked to make sure the timing chain didn’t jump (it didn’t). We then popped the valve cover to check the lifter arms to make sure we hadn’t bent a rod or rounded off the cam (we hadn’t). At that point, totally second guessing everything we knew, we got to thinking maybe we installed multiple distributors wrong. So, we pulled the distributor cap while we had the valve cover off to match number one position on the rotor with TDC and the timing mark on the engine. Guess what? They all matched up.

Now, even though we can identify a lot of 4.0L sensors, starters, and other random parts out of the Jeep by eye, and know what a lot of the bolt sizes in the engine are off the top of our heads, we know we don’t know it all. So, we started making some calls to people smarter than us (not hard to find). We all ran through the same kind of things and each time ran into the same dead end, short of taking the engine apart. Finally, we called the guys at Jeeps R Us in Laguna Hills, California. After talking it out and hitting the same wall and running out of ideas, they just said, “The hell with it, bring it down, we can fix it.” So, us being us, we said, “Um, you just ran out of ideas, how are you going to fix it?” They said, “We don’t know but bring it down. If we can’t fix it, we shouldn’t have this shop.”

Well, we gotta respect a shop that puts its money where its mouth is, so we loaded the Jeep up with all the parts, sensors, distributors, and other parts we had onto a trailer and set off. Here’s how it ended up shaking out.

Since we’d replaced all the sensors with those from a running Jeep, plus a couple of new ones from Rock Auto because the other Jeep had different plugs, we tried cranking it. The tech heard something, but Trasborg, being deaf, of course didn’t. So, out came the stethoscope to try to isolate the noise. While we never did find the noise, that old rotor sure was hitting that cap hard, and that might have been what it was. Since we’d replaced all the sensors with those from a running Jeep, plus a couple of new ones from Rock Auto because the other Jeep had different plugs, we tried cranking it. The tech heard something, but Trasborg, being deaf, of course didn’t. So, out came the stethoscope to try to isolate the noise. While we never did find the noise, that old rotor sure was hitting that cap hard, and that might have been what it was.
In bright daylight or in shadows, it helps to use a flashlight to verify where the timing marks are. Even though we’d marked the balancer and cleaned the engine-side scale, it still helps. In bright daylight or in shadows, it helps to use a flashlight to verify where the timing marks are. Even though we’d marked the balancer and cleaned the engine-side scale, it still helps.
Around this time, the dashboard started beeping like mad. We looked inside and found this. The Jeep wasn’t running, the gas tank wasn’t full, and it would have been on fire if it was really carrying 19-plus volts in the charging system. This might be a problem. Around this time, the dashboard started beeping like mad. We looked inside and found this. The Jeep wasn’t running, the gas tank wasn’t full, and it would have been on fire if it was really carrying 19-plus volts in the charging system. This might be a problem.
We knew the old distributor (which we had put back in) was bad. End play was around 1⁄4-inch, which is insane and also why the old rotor ate the inside of the old cap. It might have something to do with the oil in there too. At this point, we’d killed the battery again from all the cranking. We knew the old distributor (which we had put back in) was bad. End play was around 1⁄4-inch, which is insane and also why the old rotor ate the inside of the old cap. It might have something to do with the oil in there too. At this point, we’d killed the battery again from all the cranking.
As it turns out, our nearly dead battery wasn’t too happy being hooked up to the shop charger on the high amperage setting. We thought for sure the battery was dead, but we later tested it, and it came out just fine. Once it was charged, the tech decided just to try to swap coils again. The Jeep fired right up. It turns out we had not one, but two bad coils, both of which died from sitting and doing nothing. We still aren’t sure how that is possible. As it turns out, our nearly dead battery wasn’t too happy being hooked up to the shop charger on the high amperage setting. We thought for sure the battery was dead, but we later tested it, and it came out just fine. Once it was charged, the tech decided just to try to swap coils again. The Jeep fired right up. It turns out we had not one, but two bad coils, both of which died from sitting and doing nothing. We still aren’t sure how that is possible.
The new distributor from Rock Auto comes with this pin in it. We’ve never had a problem slamming a distributor in a 4.0L HO engine. However, this pin keeps the distributor pointed at number one cylinder. Since there is a fork where the bolt goes through, if this pin is in, the engine is at TDC, and the bolt goes through the distributor you know for sure the distributor is in correctly. It just shears off when you crank the Jeep the first time. The new distributor from Rock Auto comes with this pin in it. We’ve never had a problem slamming a distributor in a 4.0L HO engine. However, this pin keeps the distributor pointed at number one cylinder. Since there is a fork where the bolt goes through, if this pin is in, the engine is at TDC, and the bolt goes through the distributor you know for sure the distributor is in correctly. It just shears off when you crank the Jeep the first time.
Since we had the new parts from DUI, we decided to go ahead and swap plugs too. While we do like the fancier plugs, when we use a DUI coil, we always just go with the regular Champion plugs (especially in a Jeep with 258,000 miles). Since we had the new parts from DUI, we decided to go ahead and swap plugs too. While we do like the fancier plugs, when we use a DUI coil, we always just go with the regular Champion plugs (especially in a Jeep with 258,000 miles).
We gapped the plugs out to 0.070-inch, which is over what DUI recommends, but we never had problems with the 4.0L HO engines running rough at that. This is why we go with the Champion plugs with the DUI coil. More gap equals more spark, and more spark equals more fuel burned and more power. We gapped the plugs out to 0.070-inch, which is over what DUI recommends, but we never had problems with the 4.0L HO engines running rough at that. This is why we go with the Champion plugs with the DUI coil. More gap equals more spark, and more spark equals more fuel burned and more power.
The plug wires come from DUI with dielectric grease. While it is true it helps terminals not corrode, it doesn’t actually decrease resistance. Its primary purpose is to make it so that the wire ends will come off the plugs or cap if needed. It’s much like anti-seize for electrical parts. The plug wires come from DUI with dielectric grease. While it is true it helps terminals not corrode, it doesn’t actually decrease resistance. Its primary purpose is to make it so that the wire ends will come off the plugs or cap if needed. It’s much like anti-seize for electrical parts.
We contacted DUI about the coil, the shop owner spoke with them, and we told the company the whole story. The company immediately offered to send a new coil. No charge, no shipping charge. Here’s what showed up. Now, that’s service. We contacted DUI about the coil, the shop owner spoke with them, and we told the company the whole story. The company immediately offered to send a new coil. No charge, no shipping charge. Here’s what showed up. Now, that’s service.
Once that was done, it was time to button the Jeep back up. A new distributor, new-to-us coil, and some performance ignition parts and it was running better than ever. Once that was done, it was time to button the Jeep back up. A new distributor, new-to-us coil, and some performance ignition parts and it was running better than ever.
The final test was the road test. We knew we’d get it in the dirt soon enough, and because of how deaf Trasborg is, if anything was wrong in the engine, he wouldn’t hear it. After the Jeep was gone for 15 minutes, we started worrying. Then we saw this. Yes! The tech wanted to get it to full operating temperature to make sure there weren’t any electrical gremlins that got angry when they got hot. The final test was the road test. We knew we’d get it in the dirt soon enough, and because of how deaf Trasborg is, if anything was wrong in the engine, he wouldn’t hear it. After the Jeep was gone for 15 minutes, we started worrying. Then we saw this. Yes! The tech wanted to get it to full operating temperature to make sure there weren’t any electrical gremlins that got angry when they got hot.

Final Thoughts
It just goes to show you that no matter how much you know, you never know enough. Two coils died on us from just sitting there. Not only hadn’t we had that happen before, we’d never even heard of it happening before. We got so frustrated with it we were perfectly willing to pull the entire engine apart to find the problem. Sometimes it is better to just take a step back or get fresh eyes on the problem. So, thanks to Jeeps R Us for their knowledge and fresh eyes.

Sources

Rock Auto
Madison, WI 53719
866-762-5288
www.rockauto.com
Jeeps R Us
Laguna Beach, CA 92651
949-497-9183
http://www.jeepsrus.com/
Davis Unified Ignition
901-396-5782
performancedistributors.com

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