old jeep cherokee questions

[bigdee]

Re: old jeep cherokee questions NO oil pressure!!!

Re: old jeep cherokee questions NO oil pressure!!!

Drove Cheokee to town today and while I was at a stoplight the "check gages" light came on....the oil pressure gage fell to ZERO!! I gave her a little gas and the gage went past half way but when I let off the gas it went to zero again....major PANIC as I bought the car "as is" without a warranty. I drove straight to the auto parts store and bought a sending unit, installed it in about 5 minutes and problem solved,whew!!!

 

[ezbtr]

Re: old jeep cherokee questions

My 92 w/ same drive train was bullet proof, only upgrades I did were 3 row rad. and tranny cooler for towing, ltd. slip is nice to have, and yup the brakes not great so upgrade to HD rotors and semi metallic pads. I gave it to my daughter at 175K, drove like brand new, and really quick. Also ran full synthetic oil in all. The motors and tranny can easily go 250K w/ proper maint. which isnt much. I'd get 22.5 mpg while towing my tin 17' boat at 70 mph.

 

[eavega]

Re: old jeep cherokee questions NO oil pressure!!!

Re: old jeep cherokee questions NO oil pressure!!!

Drove Cheokee to town today and while I was at a stoplight the "check gages" light came on....the oil pressure gage fell to ZERO!! I gave her a little gas and the gage went past half way but when I let off the gas it went to zero again....major PANIC as I bought the car "as is" without a warranty. I drove straight to the auto parts store and bought a sending unit, installed it in about 5 minutes and problem solved,whew!!!

Ha! Mine does the same thing every so often. I turn the headlights on and off, and it fixes itself. I.m sure its something loose. I'll get to tracking it down when it becomes annoying enough.

Rgds

 

[bigdee]

Re: old jeep cherokee questions NO oil pressure!!!

Re: old jeep cherokee questions NO oil pressure!!!

Ha! Mine does the same thing every so often. I turn the headlights on and off, and it fixes itself. I.m sure its something loose. I'll get to tracking it down when it becomes annoying enough.

Rgds

Well I spoke too soon because it is doing it again. After searching Jeep forums this appears to be a common problem so I guess I will learn to live with it but it is annoying to hear the alarm every time I stop at a light. I checked the sensor and this is not a sensor at all it is just a pressure switch set at 8 psi.....so the gage is nothing more than a glorified idiot light....shame on Jeep for misleading people!

 

[MTboatguy]

Re: old jeep cherokee questions NO oil pressure!!!

Re: old jeep cherokee questions NO oil pressure!!!

Oh, I forgot to mention, the alarm comes on every once in a while! been doing it for 4 years now, never have had a problem, but it is annoying to say the least, I was going to pull it and put a regular pressure gauge in, but never did get around to it.

 

[bigdee]

Re: old jeep cherokee questions NO oil pressure!!!

Re: old jeep cherokee questions NO oil pressure!!!

Oh, I forgot to mention, the alarm comes on every once in a while! been doing it for 4 years now, never have had a problem, but it is annoying to say the least, I was going to pull it and put a regular pressure gauge in, but never did get around to it.

Yeah,it was un-nerving to see the gage go to zero until I found out that it is not a gage at all.....it has only two indications,60 & 0. I hooked the oil sender unit to compressed air to see what the ohmic value/pressure was and was surprised to see a simple on/off switch instead. The cut on was < 9 psi and that is the pressure that triggers the gage to read zero......stupid design. I might go with a mechanical gage but I don't really want that after-market look. Some might think < 9 psi is low at idle but it does not concern me that much since the hydraulic lifters are staying pumped up there has to be some oil flow. The engine is whisper quiet at idle. I thought of replacing the sender with an adjustable pressure switch and setting it at 5psi. I also thought of running 15-40 wt oil to see if that would make any difference. It has 5-30 in it right now.

 

[MTboatguy]

Re: old jeep cherokee questions NO oil pressure!!!

Re: old jeep cherokee questions NO oil pressure!!!

5-30 is my standard oil in mine and has been since I have owned it, I changed to synthetic a couple of years ago and it starts right up, clear down to -20 with no odd noises. Never have had a lifter noise ever.

 

[dolluper]

Re: old jeep cherokee questions NO oil pressure!!!

Re: old jeep cherokee questions NO oil pressure!!!

Hummm

 

[MTboatguy]

Re: old jeep cherokee questions NO oil pressure!!!

Re: old jeep cherokee questions NO oil pressure!!!

Hummm

Hummm?

 

[SuperNova]

Re: old jeep cherokee questions NO oil pressure!!!

Re: old jeep cherokee questions NO oil pressure!!!

Well I spoke too soon because it is doing it again. After searching Jeep forums this appears to be a common problem so I guess I will learn to live with it but it is annoying to hear the alarm every time I stop at a light. I checked the sensor and this is not a sensor at all it is just a pressure switch set at 8 psi.....so the gage is nothing more than a glorified idiot light....shame on Jeep for misleading people!

Yeah, it's just a pressure switch and then the PCM decides what pressure to show you on the gauge based on engine load and rpm....it's not just a Jeep "thing"..it's how Daimler-Chrysler rolled back in the day...

in '04 a common issue was typically an engine harness issue. One possible fix to try is to sister a wire from the sending unit up to the pcm...it's purple with a black tracer if I remember correctly. Don't cut the one that's there, just sister to it at the sending unit and again at the PCM.

Anybody with a '04 Ram with a 4.7 with the oil gauge dropping out has the same harness problem with the same fix...unless you want to buy and install (or pay to have installed) a new engine (and trans) harness.

 

[bigdee]

Re: old jeep cherokee questions NO oil pressure!!!

Re: old jeep cherokee questions NO oil pressure!!!

Yeah, it's just a pressure switch and then the PCM decides what pressure to show you on the gauge based on engine load and rpm....it's not just a Jeep "thing"..it's how Daimler-Chrysler rolled back in the day...

in '04 a common issue was typically an engine harness issue. One possible fix to try is to sister a wire from the sending unit up to the pcm...it's purple with a black tracer if I remember correctly. Don't cut the one that's there, just sister to it at the sending unit and again at the PCM.

Anybody with a '04 Ram with a 4.7 with the oil gauge dropping out has the same harness problem with the same fix...unless you want to buy and install (or pay to have installed) a new engine (and trans) harness.

Thanks for the info SuperNova. I will look into that but it is strange it only drops at idle. Since it is connected to the PCM you would think they would have used an analog sensor instead of a discrete switch. Even if it is working correctly it is only telling me that I have less than 9psi at idle....it is not telling me what the actual pressure is. The audible alarm is annoying and comes on every time I stop. It only does this after the temperature reaches normal or 200. I checked online and the recommended oil is 10-30 and it currently has 5-30 in it so I may change to the correct weight and see what happens. I am also going to hook up a mechanical gage to see what I actually have. The engine is quiet at idle and runs flawlessly and it got 22 mpg on a 100 mile trip yesterday. From what you described is it possible it could be the PCM or gage?

 

[SuperNova]

Re: old jeep cherokee questions NO oil pressure!!!

Re: old jeep cherokee questions NO oil pressure!!!

Sure it's possible, bigdee. All the stuff you are saying is all the stuff I thought the first time I had to diagnose one in the shop. Took me 3 comebacks to get it figured out. I even load tested the harness in the vehicle and couldn't find the fault. But process of elimination led me to believe the harness had an intermittent high-resistance in that circuit. After the old harness was out, I was able to bench test it and found the fault. The new harness did fix the truck. After that they came out with a bulletin about it. It's only on the oil pressure circuit and therefore the best non-warranty fix is to sister the wire. I admit that I also checked the actual oil pressure with a gauge to make absolutely sure the pressure wasn't actually dropping below spec at idle. Although now that I think about it, I think I remember the 4.0 jeeps had a problem with the oil pickup screens getting blocked with debris fairly easily, so I think I would definitely put a gauge on it and make sure you have pressure.

FWIW: 5w30 oil is only thinner than 10w30 when it's cold, once it gets warm they have the same viscosity. If you want thicker oil warm you'll have to go to 10w40

 

[MTboatguy]

Re: old jeep cherokee questions NO oil pressure!!!

Re: old jeep cherokee questions NO oil pressure!!!

FWIW: 5w30 oil is only thinner than 10w30 when it's cold, once it gets warm they have the same viscosity. If you want thicker oil warm you'll have to go to 10w40

Living in Montana, is the reason I use 5w30, makes for easier starts in the cold winter months.. The first year I lived here, I actually ruined the engine in my Bronco, using the wrong oil, 6 months of cold and the mains were worn out!

 

[SuperNova]

Re: old jeep cherokee questions NO oil pressure!!!

Re: old jeep cherokee questions NO oil pressure!!!

Living in Montana, is the reason I use 5w30, makes for easier starts in the cold winter months.. The first year I lived here, I actually ruined the engine in my Bronco, using the wrong oil, 6 months of cold and the mains were worn out!

5w30 is standard oil in most everything these days and has pretty much replaced 10w30. Like I said, it flows better when the engine is cold and has the same viscosity as 10w30 (or straight 30 weight for that matter) once the engine gets to operating temperature. 5w20 is a little thinner and should probably only be used in engines designed for it.

 

[bigdee]

Re: old jeep cherokee questions NO oil pressure!!!

Re: old jeep cherokee questions NO oil pressure!!!

Sure it's possible, bigdee. All the stuff you are saying is all the stuff I thought the first time I had to diagnose one in the shop. Took me 3 comebacks to get it figured out. I even load tested the harness in the vehicle and couldn't find the fault. But process of elimination led me to believe the harness had an intermittent high-resistance in that circuit. After the old harness was out, I was able to bench test it and found the fault. The new harness did fix the truck. After that they came out with a bulletin about it. It's only on the oil pressure circuit and therefore the best non-warranty fix is to sister the wire. I admit that I also checked the actual oil pressure with a gauge to make absolutely sure the pressure wasn't actually dropping below spec at idle. Although now that I think about it, I think I remember the 4.0 jeeps had a problem with the oil pickup screens getting blocked with debris fairly easily, so I think I would definitely put a gauge on it and make sure you have pressure.

FWIW: 5w30 oil is only thinner than 10w30 when it's cold, once it gets warm they have the same viscosity. If you want thicker oil warm you'll have to go to 10w40

Thanks again....I will try 10-40. The pressure switch CLOSES on low pressure so I would think that a high resistance would show high? If that does not solve the problem NAPA has a oil sender set at 3-5 psi for $7

 

[SuperNova]

Re: old jeep cherokee questions NO oil pressure!!!

Re: old jeep cherokee questions NO oil pressure!!!

Thanks again....I will try 10-40. The pressure switch CLOSES on low pressure so I would think that a high resistance would show high? If that does not solve the problem NAPA has a oil sender set at 3-5 psi for $7

On the Ram trucks it's a NO switch and closes with pressure.

 

[dockwrecker]

Jeep gauges are notoriously funky. My Cherokee fuel gauge likes to play dead right after I fill up unless I hold the key in the start position an extra second. Once it burns off 3-4 gallons it's fine. Been that way for 11 years now and I've tried everything to fix it. Hard to do but I've learned to ignore it. Glad it's not my oil gauge or I'd go nuts! Like you're doing!

 

[LippCJ7]

Re: old jeep cherokee questions

Just listen to your Cherokee, it will tell you if there is an issue, hear the lifters clattering you need oil blah blah blah, Best advice I can give you is lift it a bit 3" or so and get some bigger tires, look at a locker in the rear, Cherokees that are not 4X4 are a Communist ploy to undermine the US Government and should be destroyed immediately, the Cherokee is one of THE BEST off the shelf 4X4's you can buy and you will be hard pressed to find anything better for the money. Don't be gentle with it, drive it like you stole it!! Absolutely GREAT low cost SUV that never got its just deserves as a one of the Great Modern 4X4s!

 

[bigdee]

Re: old jeep cherokee questions

Well I rigged up a pressure guage, used a refrigeration gage set as a temporary diagnostic gage.....did not like what I saw 50psi cold @ 2000 rpm and 30psi @ cold idle.....hot 40 psi @2000 rpm and 4 psi at hot idle.
I changed the oil to 15-40 and the hot idle pressure increased a bit to 10 psi. I found a few and VERY small gold colored flakes in the drained oil.
I am afraid I have a spun bearing. The strange thing is the motor is very quiet for a 4.0 I-6 jeep engine. OH well, I will continue to drive it until I hear noises.

 

[SuperNova]

Re: old jeep cherokee questions

Well I rigged up a pressure guage, used a refrigeration gage set as a temporary diagnostic gage.....did not like what I saw 50psi cold @ 2000 rpm and 30psi @ cold idle.....hot 40 psi @2000 rpm and 4 psi at hot idle.
I changed the oil to 15-40 and the hot idle pressure increased a bit to 10 psi. I found a few and VERY small gold colored flakes in the drained oil.
I am afraid I have a spun bearing. The strange thing is the motor is very quiet for a 4.0 I-6 jeep engine. OH well, I will continue to drive it until I hear noises.

I don't believe you've SPUN a bearing...YET! You may have a couple of worn bearings that need to be replaced, but if you do it now, you'll probably save the engine. If you wait until it starts making serious noise, it will probably be too late to save anything.