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Unread 07-15-2013, 08:07 AM   #16
dellis
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2tall2slow, I know you said that you are you new to mechanics and working on your car. You are experiencing driveablity problems that are most likely electrical in nature - and this means that there are 100 to 200 different reasons why you are having this failure involving about two dozen parts, dozens of connectors, and scores of wires. Electrical failures are not as easy to diagnose as are mechanical failures. With mechanical issues, you can usually narrow in on the problem based on symptoms ... but, with electrical issues, the same symptoms can related to dozens of problems. Just because one person says, "I had that same electrical problem and it was this thing." may or may not apply to your problem (I see this all the time).

Regardless, generally people take one of two approaches: (1) diagnosing the problem with diagnostic tools, and repairing the damage, or (2) guessing at what might be wrong, and replacing parts or cleaning things until it gets fixed. #1 requires lots of patience & a multimeter and #2 requires lots of money and luck.

If #1, then please answer again my question from several days ago when I said the most important first step is pulling codes (you said that the CEL came on again, and I'm assuming that you cleared off the low battery code from earlier). If you did that, your next step would be to check the fuel pressure at the rail DURING a stall condition, or just after a stall condition.

If #2, and assuming you fully went through the cleaning parts of the Dirty Dozen (e.g. grounds, PDC contacts, battery terminals) then here are the remaining parts that you can replace that impact driveability, in my best guess of most frequent to least frequent failures:
(a) Replace your PCM with one that is remanufactured or guaranteed functional from a junkyard. Avoid the Florida/internet guys. Alternatively, tear into your PCM and resolder the connections.
(b) Replace your fuel pump assembly ... the whole assembly.
(c) Replace your crankshaft position sensor with a Mopar sensor
(d) Replace your engine's wiring harness (accounts for shorts and broken wires at connectors)
(e) Replace your camshaft position sensor
(f) Replace your ASD and Fuel Pump relays, or switch them with a known good relay (horn, A/C)
(f) Replace your alternator
(g) Replace your MAP sensor (accounts for random short on 5V reference to CKPS)
(h) Replace your TPS sensor (accounts for random short on 5V reference to CKPS)
(i) Replace your spark plugs, assuming you did not put in copper plugs and instead are running "advanced" plugs that introduce excessive kickback into the coil driver.

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Unread 07-15-2013, 08:19 AM   #17
Uniblurb
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Quote:
Originally Posted by 2tall2slow View Post
Since i replaced my plugs and wires, ign coil its drove a good distance over two days. This morning i made it a quarter mile down the road and it kicks...then rpm hand jumps around..then jeep lost power. Cel came on so i came to a stop, put in park and re-cranked it. Started fine and got me home. Dirty dozen link was helpful, so after checking thru all of that, now what? Need a fix, spent my entire check, the family is in need of a solid ride. Any advice??
Believe dellis already asked if your gauges are acting erratic? Are the rpms on your gauge jumping around with the actual rpms of the engine? Do you notice your gas gauge sometimes reading empty with the warning light coming on?

The reason I ask is sometimes a bad crank sensor will cause havoc with your gauges, particularly the voltage gauge and sometimes the gas gauge. And often a bad crank sensor won't throw any codes. Below is a crank sensor test (4.0 & V8's) using a multimeter set to the lowest ohm setting. Unplug your sensor at the back/passenger side of the block on you 98 4.0 and have the locking tab up. Then place the black probe on the B pin (middle ground cavity) and red probe on the C pin (right side of connector, power). Any resistance at all and you have a bad crank sensor and only go for Mopar as a replacement if it tests bad.

Saw where you went through ZeeJays excellent thread on stall/no-start problems but did you actually clean all your grounds? The ones on the block are critical to have clean, especially one of the ones on the coil stud which grounds the PCM, which in turn grounds all the sensors. Suggest cleaning them if you haven't already and good luck!
crankshaft-positon-sensor-test-p.-8d-8-fsm.jpg

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96 4.0 ZJ Laredo, 2004 4.7L WJ Limited, 93 4.0 XJ (spare), 96 4.0 XJ (son's)

-Stalling ZJ? 12 things to check before replacing a sensor; the Dirty Dozen
-Crankshaft position sensor multimeter test. & video of testing.
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Unread 07-15-2013, 09:47 AM   #18
2tall2slow
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Rpm gauge goes erratic, not actual engine. Does tht mean i can eliminate crank sensor? Also Grounds for pcm did not clean or check. Will do after work.
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Unread 07-15-2013, 10:56 AM   #19
dellis
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Quote:
Originally Posted by 2tall2slow View Post
Rpm gauge goes erratic, not actual engine. Does tht mean i can eliminate crank sensor? Also Grounds for pcm did not clean or check. Will do after work.
Your crankshaft sensor is one of the electrical elements that affect your tachometer's (RPM gauge) operation - in fact, the crankshaft position sensor is what measures your RPM. So, in the midst of diagnosing your driveability issues, you cannot eliminate it.

If your tachometer (RPM Gauge) is erratic, then does this mean that it is your crankshaft sensor? No. It could be a dozen things. The image below shows you all the things that have to be properly working in order for the tachometer to function properly (the CMPS, camshaft position sensor, does not need to operate in 96-98 ZJs but not sure of 93-95 ZJs).

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Unread 07-15-2013, 06:25 PM   #20
2tall2slow
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Pulled my pcm out today. traced a ground point and boy was it a dirty oily mess. Cleaned and reassembled. cant actually test its contacts w a meter, dont have access to one. was hoping maybe bad sauter easy fix...well i went to start my jeep and it ran for a few seconds and died. tried again and it ran..then dies. all the while rpm gauge goes eratic.third times the charm right? Nope. it wont turn over at all now. at least before i could drive it, now it wont crank. cel isnt on, abs lights up briefly and goes off. idk people, i feel i have exhausted my mind and efforts for now, i just dont understand. kinda felt like it just wasnt getting gas or something. i mean it would crank, just not catch and fire up. does this sound like asomething particular?? Remember, i'm new at mechanics.
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Unread 07-15-2013, 08:29 PM   #21
dellis
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It sounds like all the stuff in my list above. Seriously, it could be a lot of things. These sort of problems are not as simple as "here is the symptom and here is the fix". Instead, symptoms can be any one of a dozen problems, and any particular part might have a half dozen different symptoms. So, you either have to do diagnostics or guessing. (I personally don't believe in just guessing and replacing parts.)

If you don't have access to some basic tools to do diagnostics/tests (e.g., a multimeter or even a voltage light, and a fuel pressure gauge), then it is going to be frustrating for you as a mechanic ... but, honestly, even a basic digital multimeter can be purchased for $20 to $25, and that's a good long term investment, particularly for owning a Jeep. If you don't have that, maybe AdvanceAuto or PepBoys or AutoZone will have these things to rent or loan to you.

But, if you insist on guessing without any tests, I would say your three most likely causes of this (in order of cost) are crankshaft position sensor (30% chance), fuel pump (25% chance), and PCM (30% chance) ... and, there's a 15% chance it is something else. These are wild guesses based on observing lots and lots of posts about stalling & no-start problems.

P.S. The solder fix on a PCM is not entry level repair work - it is fairly advanced and requires use of a torch. I've done it, but I'm an electrical engineer with lots of soldering experience.
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Unread 07-15-2013, 09:12 PM   #22
2tall2slow
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A good friend of mine will be soldering for me, if need be. He also ia electronic tech. Was actually looking at Dmm's, very affordably for basic model. Thanks for the continuous help, dont give up on me yet..i'm not.
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Unread 07-15-2013, 09:23 PM   #23
ZeeJay1997
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Retrace your steps. Did the PCM connectors locks snap when you reseated them? You have to rock them a little to get them in all the way. Check the ground wires for damage.

If you actually did all the things i suggested in the dirty dozen , given what you are reporting now, I suspect the PCM solder joints or the connectors. you may want to try the socket restoration that i mentioned in #1 of the DD.
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Unread 07-16-2013, 06:20 AM   #24
2tall2slow
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It seems like my pcm connection are nice and tight, not drooping or loose like some have described. They fit tight and snug. i plan on investing in a multimeter today and, like u suggest, retrace my steps. I can look and clean all day long, but unless i obtain a dmm, i feel like i am looking for a needle in a haystack.
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Unread 07-16-2013, 08:02 AM   #25
Uniblurb
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Just curious if when you removed the PCM/cables did you also disconnect the neg terminal on the battery? Maybe it says it in Zee's thread but every time you disconnect the PCM, sensors, or do any electrical work the battery cable needs disconnected.

Also since your engine won't crank, and CL not lighting up briefly when turning the key on, are you sure your battery isn't just dead from cranking? Do your lights still work or is the starter clicking? You may also have blown a fuse with no power whatsoever if the battery isn't dead.

You'll feel a whole lot less frustrated once you buy a multimeter and can do some testing. Another real handy inexpensive tool is a DC voltage test light and suggest buying one for $10 or less. You can find one at about any auto parts store or hardware store. A multimeter can do the same thing but a test light is so much quicker where you just connect it to a ground and check for voltage.

Here's one that's a little fancy for $10 and you may want to watch the video how it's used. I just have a white light one and can go right down a whole fuse bank quickly testing each fuse on the back to see if it has power instead of having to pull them.

http://www.autozone.com/autozone/acc...er=186543_0_0_

Hang in there, plenty of people here to help, and good luck!

Edit: also meant to say when you buy a multimeter buy a couple cheap jumper wires with aligator clips on the ends for connecting to the meter probes. Think I spent $2-$3 at Walmart for a pair w/black and red wires.
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96 4.0 ZJ Laredo, 2004 4.7L WJ Limited, 93 4.0 XJ (spare), 96 4.0 XJ (son's)

-Stalling ZJ? 12 things to check before replacing a sensor; the Dirty Dozen
-Crankshaft position sensor multimeter test. & video of testing.
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Unread 07-16-2013, 08:15 AM   #26
dellis
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Quote:
Originally Posted by Uniblurb View Post
Edit: also meant to say when you buy a multimeter buy a couple cheap jumper wires with aligator clips on the ends for connecting to the meter probes. Think I spent $2-$3 at Walmart for a pair w/black and red wires.
^^ This. I use those things a lot.
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Unread 07-16-2013, 08:22 AM   #27
2tall2slow
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Actually i forgot to disconnect battery just before i pulled pcm cables, but did disconnect soon after. Did i fry my pcm doing that?
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Unread 07-16-2013, 08:26 AM   #28
dellis
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Originally Posted by 2tall2slow View Post
Actually i forgot to disconnect battery just before i pulled pcm cables, but did disconnect soon after. Did i fry my pcm doing that?
Not likely, and I wouldn't worry about that. Battery disconnection is more of a safety issue than anything else ... it is only twelve volts, but there is enough current behind it to weld (which, by the way, is also why you want to cover up your positive battery terminal with a towel when working on the engine).

Electrical damage to electronics happens with high energy spikes. You are more likely to damage electronics with static electricity.
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Unread 07-16-2013, 06:35 PM   #29
ZeeJay1997
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To make great jumper wires, next time you are at the JY, find a ZJ and cut some of the connectors out. Take them home and make you some custom ZJ gremlin hunting super jumpers.
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Unread 07-16-2013, 06:48 PM   #30
ZeeJay1997
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Quote:
Originally Posted by 2tall2slow View Post
It seems like my pcm connection are nice and tight,
They can feel tight when the socket tension is weak. An off the cuff test is to get a Pamona #20 banana adapter, insert it into each socket. The adapter should have the same tension in each socket
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