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Old 11-03-2008, 11:46 AM   #1 (permalink)
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ZJ - '95 Jeep Grand Cherokee Laredo Upcountry
90 day: 20.57 mpg (US)

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90 day: 33.46 mpg (US)

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90 day: 16.4 mpg (US)

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Battled a non-drivable Jeep for 2 months

And the other day, I BEAT IT!!!!

While taking my daughter to college with it, it started running poorly and losing power. Was hard to keep at an idle and just wasn't wanting to rev. So, time to troubleshoot. Its a 1990 Jeep Cheroke with 4 liter 6 banger and automatic. Because I had spark at all six plugs I ruled out basic ignition issues, though I replaced the distributor cap and rotor, and plugs and wires. I used a timing light to see if the timing chain was at issue, nope, rock steady. I had fuel at the fuel rail. I went through the tangles mess of vacuum lines, checking everything. No problems there. So I started looking at sensors.

With 199,000 miles on it, it had been running strong to this point and the motor had always sounded good. No ugly crankcase noises. Replaced the O2 sensor and the Throttle Position Sensor. No change. Ran a compression test. Well, had two cylinders down on compression. OK, headgasket. Took me a while to finish this task as I became ill and then had minor surgery to my ear and sinus. And of course, there was some level of don't care too.

Finished the headgasket, but no change when I started it up. I have a parts Jeep that I'm stripping, and so I started grabbing parts and swapping them around. I swapped fuel injectors and fuel rail and fuel pressure regulator, and the throttle body and checked and cleaned the Idle stepper. Then I bought a Crank Position Sensor. No change again. I swapped from the parts rig, the ignition control module, and then the distributor (which has the cam sensor inside it...), all to no change. All I had left was fuel pump or computer, and computers don't normally go bad in these.

So pulled the fuel pump out. Hey whats this? There is this little 3" piece of 3/8" hose between the pump and the output tube. And it was rotten, cracked, and very soft. In fact, without loosening the clamps, it was pulled off the fittings with a finger. On one side it was just barely making contact with the tube. Well this MUST be the problem... Replaced the hose, and just for my own edification, ran both that pump and the one from the parts Jeep and both pumped fuel between gas cans. Very nicely at that. I put the original pump back in with the new section of Goodyear fuel injection hose and a new clean strainer.

And the Jeep started and settled into a nice smooth idle. Took it for a drive, and it is quite nice to drive, better than anytime since I bought it. So while my peformance is better than ever, I imagine fuel mileage will be better too.

Next tool purchase will be a fuel pressure gauge. I could see I had fuel pressure at the rail, but now realize that with a gauge, I'd have a better picture what was going on.

On the other hand, I now have a bunch of spare parts in case something happens to me or a buddy on the trail. And the Jeep got one helluva tune up.

Rock on guys.

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Old 11-08-2008, 11:26 PM   #2 (permalink)
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Ha ha! Yeah, no wonder it runs so good with all you did to it! Congrats on finding the culprit. Good read.
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Old 11-09-2008, 02:24 PM   #3 (permalink)
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I'm wonder if my Jeep is starting to have the same problem. It has some what of a delayed start to it. And when I shut it down I hear a noise coming from the fuel tank. Like when you pour a bottle of liquid out really fast and the air bubble has to catch up to fill in the space. Kind of a plunking sound for lack of a better word for it. I've also noticed my idle isn't very stable.

The sad part is it's not something I feel I have the tools or place to do it myself so I think I'll have to take it in to fix it. I talked to a mechanic friend of mine and he said it would probably cost about $200 just to drop the tank so I might as well have the pump/filter replaced as well.
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Old 11-11-2008, 01:55 AM   #4 (permalink)
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Join Date: Feb 2008
Location: Tooele, UT
Posts: 412

ZJ - '95 Jeep Grand Cherokee Laredo Upcountry
90 day: 20.57 mpg (US)

Neon - '03 Dodge Neon SE
90 day: 33.46 mpg (US)

S'Crew - '02 Ford F150 Supercrew XLT
90 day: 16.4 mpg (US)

Ranger - '90 Ford Ranger
Last 3: 28.02 mpg (US)

Not the Jeep - '03 Dodge Neon SE
90 day: 34.11 mpg (US)
Thanks: 7
Thanked 13 Times in 8 Posts
I hope your troubles aren't in the tank. I'm lucky that the earlier Cherokees have the pump accessible without dropping the tank. I know on my Grand Cherokee, if I ever have fuel pump isses, I'm cutting a hole in the floorso I don't have to drop the tank, and then seal the hole with some sheetmetal and RTV.

I'll admit its intimidating to drop the tank, but I've dropped tanks on a few vehicles. And of course, they are always full. It all comes down to what you are comfortable with. Not everyone should do this.

I forgot to add a pic of the little chunk of fuel line.

Yes, this is the culprit to my troubles.

Anyway, to finish this tale, the Cherokee was turned back over to my daughter this weekend. I drove it all last week with no issues, and my daughter drove it all weekend. Last night she took it back to college with her and it managed the 2.5 hour drive very nicely. I think the Jeep is running a little cool so I'm going to replace the thermostat over XMas break. I'm not sure it makes it to closed loop. My daughter will be monitoring its mileage...

Now, back to my own Grand Cherokee. I already moved from 30" to 31" tires, and will be adding a 2" lift very soon. I'm hoping to not lose much in mileage. But we'll see.
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Old 11-11-2008, 01:13 PM   #5 (permalink)
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Quote:
Originally Posted by zjrog View Post
I think the Jeep is running a little cool so I'm going to replace the thermostat over XMas break. I'm not sure it makes it to closed loop. My daughter will be monitoring its mileage...
Block off a couple of the grill openings for her. It makes a world of difference. The 4.0L Jeeps take forever to fully warm-up with the cooling setups they have. If your worried about her not watching it I had 4 blocked off most of the summer(up to the 90's around here). She'll enjoy the extra fast heat.
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Old 11-11-2008, 09:05 PM   #6 (permalink)
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Join Date: Feb 2008
Location: Tooele, UT
Posts: 412

ZJ - '95 Jeep Grand Cherokee Laredo Upcountry
90 day: 20.57 mpg (US)

Neon - '03 Dodge Neon SE
90 day: 33.46 mpg (US)

S'Crew - '02 Ford F150 Supercrew XLT
90 day: 16.4 mpg (US)

Ranger - '90 Ford Ranger
Last 3: 28.02 mpg (US)

Not the Jeep - '03 Dodge Neon SE
90 day: 34.11 mpg (US)
Thanks: 7
Thanked 13 Times in 8 Posts
I might try this when she is home over Thanksgiving. I don't want to try something she won't know how to undo...

Over Thanksgiving her Jeep will also be getting 235/75R-15s and some matching wheels to replace the 3 different types of wheels and mismatched 215/75R-15s.


I had put this set on, but they rubbed when turning and stuck just a little outside the flares. Not good for aero, and not legal either.

So I'm yanking these off the parts Jeep (Actually, I'm referring to it also as the recycled Jeep, as the shell will become a camping trailer...).

These are a factory size and factory wheels, will stay tucked in better.

And when I do the tires it too will receive a 2" lfit. Sorry, its in keeping with my post apocolyptic thinking, have to be able to get over things, and be able to reach our campsites. This vehicle doesn't need a lot of lift or really big tires. 235s and 2" will be sufficient.
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Last edited by zjrog; 11-11-2008 at 09:31 PM..
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Old 04-08-2009, 09:44 AM   #7 (permalink)
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Join Date: Feb 2008
Location: Tooele, UT
Posts: 412

ZJ - '95 Jeep Grand Cherokee Laredo Upcountry
90 day: 20.57 mpg (US)

Neon - '03 Dodge Neon SE
90 day: 33.46 mpg (US)

S'Crew - '02 Ford F150 Supercrew XLT
90 day: 16.4 mpg (US)

Ranger - '90 Ford Ranger
Last 3: 28.02 mpg (US)

Not the Jeep - '03 Dodge Neon SE
90 day: 34.11 mpg (US)
Thanks: 7
Thanked 13 Times in 8 Posts
HA! Still haven't done the lift, and my daughter doesn't keep me informed on its mileage. It has one issue that will be resolved soon. It likes to die when slowing. Done it baout 4 times now, it always starts right up. There is an adjustment for the TPS, and it has behaved better in the last month (no dying means better), but I have a different throttle body that I have slightly modified that should cure it. Otherwise, the little Jeep is doing well and that, makes me happy...

And the parts Jeep was chopped up, the rear section went to a friend to turn into a trail trailer and the rest went to a metal recycler. I have a bunch of parts from it for the yella heep, and the front axle is going under my 4 banger Ranger very soon... Recycling...

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Last edited by zjrog; 04-08-2009 at 09:55 AM..
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