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Unread 09-15-2010, 11:55 PM   #31
AUSjeepzj
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Quote:
Originally Posted by freakinheep89 View Post
also, a no power to coil is the main symptom of a CKS fault(crankshaft position sensor), have you eliminated that as an option?
I replaced the CPS with a new one and no change also tested the auto shutdown relay and it seems to be working fine.

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Unread 09-16-2010, 12:01 AM   #32
iPlay1515
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Quote:
Originally Posted by AUSjeepzj View Post
I replaced the CPS with a new one and no change also tested the auto shutdown relay and it seems to be working fine.
If the auto shutdown relay is working properly, and there is no power to the coil, that leaves the fuse, and the wiring from the auto sd relay to the coil.

The engine will not start unless there is constant power to the coil when the ignition switch is on. Nothing else really matters until the coil has power.
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Unread 09-21-2010, 12:26 AM   #33
tonymartin
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So I take it this will work for both the 4 banger and the 5.2? I have just ordered a bloody fuel pump too. Ah well, lets see eh?

Nice write up though mate!
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Unread 09-21-2010, 12:35 AM   #34
freakinheep89
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Quote:
Originally Posted by tonymartin View Post
So I take it this will work for both the 4 banger and the 5.2? I have just ordered a bloody fuel pump too. Ah well, lets see eh?

Nice write up though mate!
no 4 banger in the ZJ's, you mean 4.0? and yes it should work in all of them
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[SIZE="1"][B]95 ZJ 5.2[/B]- D30/XJ shafts/D35 Yukon alloys,249, 2"BB, 30x9.5"Wildcat EXT,lots of motor mods, rancho shocks & stabilizer.[/SIZE]

[QUOTE=slayercr23;12630497]How would i go about Stroking it?[/QUOTE]
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Unread 09-24-2010, 05:39 PM   #35
plastic55
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large writeup in wrangler forum. Did this repair on a 2.5 a couple of years ago. Used this thread to http://www.jeepforum.com/forum/f12/9...90788/diagnois.

If memory is correct. If you hear the fuel pump the car will start. Another test is - turn the key to on -wait five minutes try to start the truck. Mine got so bad that i had to wait 15 minutes. I think the fuel pump sound was the tell tale sign that everything was ok but it could of been another relay sound. The waiting cuts down on draining the battery. First clue was the jeep started right up after being towed home from the airport after returning home on cold winter night. I had left the key on during the tow.

I potted with a two part urethane mold forming material with a durometer of 40. Work uses it to make fixtues to hold parts. Available at hobbie shops

The wrangler still start rights away with 198,000 miles. As the weather changes and it get colder the problem will get worse.
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Unread 10-01-2010, 03:02 PM   #36
SouthSeaPirate
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Does this fix help with lazy starts? I dont have a no start issue, it just takes a few revolutions before it fires up... This sound like a cap problem?
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Unread 10-01-2010, 09:44 PM   #37
JrMechanic
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Quote:
Originally Posted by SouthSeaPirate View Post
Does this fix help with lazy starts? I dont have a no start issue, it just takes a few revolutions before it fires up... This sound like a cap problem?
Do you hear your fuel pump prime when you first turn the key? If not then yes, you do have faulty capacitors.
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Unread 10-02-2010, 07:21 AM   #38
SouthSeaPirate
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Im pretty sure I do hear it prime right off the bat. But if a wait a few seconds after I turn the key it will fire right up.
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Unread 11-20-2010, 11:19 AM   #39
canuckcj
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Thank you for all the good info guys. This is the only listing Google came up with that described my problem. I ordered my capacitors from mouser.com because they are rated for the correct temperature. It took me about an hour to do today and it worked like a charm!

I did not get the capacitors from Radio Shack as the ones they have are only rated to 85 degrees. The whole process took about an hour to do but you might be able to do it faster if your better with the soldering iron. I'm a novice at the iron so anyone can do this.

I used a razor blade and it came out very easily. A small toothbrush helps to clean things up a bit as well.

I did not see anything obvious wrong with the capacitors that were in there. The tops were not domed and I could find no leaks. Possibly 2 of the 3 were a little domed on the bottom side.




Once the new capacitors were in I siliconed everything up nicely, hooked it back up and she fired right up.
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Unread 11-20-2010, 11:24 AM   #40
canuckcj
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I just thought I'd share my experience with this. Also because if someone else hadn't taken the time to post their experience I'd be $200 shy in my wallet.

Recently my 4.0 from a 94GC stopped running. I hadn't changed any wiring but the fuel pump no longer primed when the ignition was turned on. I spent hours re-tracing wires and checking connections and came to the determination that the issue was in the PCM. Frustrated at not getting it to run as I needed to get antifreeze rather than water in the block before winter hits, I was sitting there thinking on it and the relay for the ASD starts to click. It progressively clicks faster and faster until it locks in and the fuel pump primes. huh?? Okay, crank and it starts up. I get the antifreeze in it let it warm up and shut it off. I come back an hour later and again no prime, no run. I let the key sit on for a few minutes and it does the click thing again and the pump primes.

Some searching around turned up a TSB on my model PCM

TSB
1993 - 1995 Jeep Grand Cherokee 4.0L
1993 - 1995 Jeep Grand Cherokee 5.2L

Symptom: Will not start immediately in cold ambient temperatures, no MIL immediately at key on, no communication with scanner, auto shut down (ASD) relay is clicking. Wait for awhile with key on and MIL comes and and then it will start.

System: Emissions/PCM/Fuel

Codes: N/A

Problem: When the ambient temperature drops below 40 degrees, the Powertrain Control Module (PCM) fails to power up until warmed up or key is left in the on position, the MIL comes on and the relays start clicking.

Test & Fix: If the problem cannot be duplicated, remove the Powertrain Control Module (PCM) and cool it in a freezer. Reinstall the PCM and check if symptoms are present. If symptoms are present and powers and grounds are OK, replace the PCM. "


This certainly sounded like my issue but I wasn't keen on replacing the PCM as Autozone wants $200 for a new one. Some more searching around Jeep forums turned up this post.

It was certainly worth a shot as I already have a soldering station and electrical parts are cheap.
All said and done, it absolutely works! No more lazy PCM and I saved myself a few hundred bucks and instead spent $6.00 on capacitors shipped from mouser.com.

I did not get the capacitors from Radio Shack as the ones they have are only rated to 85 degrees. The whole process took about an hour to do but you might be able to do it faster if your better with the soldering iron. I'm a novice at the iron so anyone can do this.


These are the capacitors in question. You have to dig out the gel pack from around them. I used a razor blade and it came out very easily. A small toothbrush helps to clean things up a bit as well.

I did not see anything obvious wrong with the capacitors that were in there. The tops were not domed and I could find no leaks. Possibly 2 of the 3 were a little domed on the bottom side.



Once the new capacitors were in I siliconed everything up nicely, hooked it back up and she fired right up.
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Unread 11-21-2010, 03:54 PM   #41
stancomm
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About the caps

Bad caps do not need to look bad to be bad. They slowly, over time loose their capacitance, the effective value becoming smaller. Do a Google search on E.S.R., 'effective series resistance', to see why.
As regards the temperature rating, VERY important in an under-hood application.
I do 2-way radio work and have a bag full of trashed 47 mic 25 volt caps, all rated for 85deg C. These came out of radios installed in school busses which are big yellow pizza ovens in the summertime.
They would loose value and eventually leak their guts all over the place. The leakage IS CORROSIVE to the copper land patterns on the board actually etching circuits open! And under all that sealant... well, if that happens there's no way to replace the lost wiring, just buy a new one!
Incidentally, the manufacturer of that radio eventually did get the message... the third production run of that box was using the 105C guys.

Good article, thanks!

Stan
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Unread 01-21-2011, 12:18 PM   #42
farmermark
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I found that using bamboo skewers worked great for removing the gel from both sides of the board. Less chance of ruining traces on the board.
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Unread 03-01-2011, 10:31 PM   #43
LagartoJuancho
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Hi there.

My XJ (though it's papers state it's a 97, it has the pre-97 trim, marker lights and dashboard, go figure) seems to have this exact problem. I've had it for 4 years now and it has performed admirably, but developed this problem since around 3-4 months ago:

The check engine light (which should come on for a couple seconds before starting) doesn't come on. If I try to start it right away, it will crank forever and won't start, but if i leave the key at "on" for a LONG while (it varies) without giving it start, turn key to off, then on several times, it'll get to a point when the check engine (and a relay under the hood, i guess the ASD) begin to click rapidly, then progressively slower until the check engine light stays on solidly for a while then goes to off. After a couple more magic passes I crank it and it starts right away, and it runs like a champ after that.

Fuel pressure doesn't build up until the "clicking" phase is over, after that is plenty. Spark is good. It has brand new pump, distributor cap and rotor BTW, all of them changed part because I was diagnosing this problem, part because it was already time for new parts.

Another clue I think points to this same cap problem: whenever i try to start it on a sunday afternoon, after it's scorchingly hot inside from all the sunlight (Venezuela, coastal town, sea level), it starts much more easily... Maybe the the busted caps' remaining electrolyte complies a bit when it's hot?. Monday mornings? No such luck. I need to get up early to do some extended "foreplay" with the XJ

My XJ has the dull metallic grey type PCM, the one with 3 connectors (1 each gray, white and black), fixed by 3 5/16 screws besides the air box near the radiator.

I'm proficient enough to change a bunch of caps like in this writeup, but I'd truly appreciate to know if anyone here has done this kind of repair on that newer type PCM. Logic indicates it shouldn't be much different, but surely the circuit layout and/or components have changed. You know, some intel before messing with it.
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Unread 03-02-2011, 07:33 AM   #44
JS97ZJ
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Thi PCM fix does not pertain to your 3 connector type PCM.
Start a new thread, and restate the problem. It doesn't sound like it's PCM related. ?
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Unread 03-02-2011, 07:55 AM   #45
Dyn0mitemat
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I had the exact problems described in this thread in my 98 zj (3 plug pcm) and I pulled it apart with no luck. There was only one cap in it and it tested good.

Ended up replacing it and everythings been bliss since.
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