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Unread 08-12-2013, 09:00 PM   #1
fourwheelnguy
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YJ Computer/ Engine Swap Help

Hey guys, I need help again...

Background...I have a 1994 Wrangler with the 2.5L, 5 speed manual in it. Ran in until ~203k on the clock. New engine time came and I chose to stay with the 2.5L (yes I know some will chuckle) but honestly the four squirrels always did what I asked them to do, it was in my price range, and I was hoping it would be something fairly simple and would be heading back down the road. The last statement is anything but true.

Long story short it's been in the shop for the last two months, they can't get it to start on a regular basis, sometimes it will and sometimes it won't, doesn't appear to be any rhyme or reason to it. The shop has replaced nearly every electrical component on the Jeep, made new grounds, sanded the grounding spots, checked the entire harness out of the loom etc etc.

They are suggesting I may have a bad ECM (I had done the "brain" surgery on my ECM a couple years ago and it has worked great!) Anyways, I'm fortunate to have several Jeepers in the area that are willing to part with their ECM from when they did an engine swap and eliminated it.

My question is (and I searched through over 10 pages of posting before making this one as I don't want to waste anybody's time; so I apologize in advance if I missed it or didn't hit the right crawlers) does the part number on my, currently installed, ECM have to match the one I put in it? Before I purchase one from somebody I would like to make sure it will work... My ECM has a part number of 56028289, the dealer said the only ECM that would work would be this one or 56027575; is that true? Unfortunately those who have offered me an ECM don't have those part numbers.

As always your help and expertise is greatly appreciated!!! My wife may off me if I don't get her on any Jeep rides this Summer and it's coming to an end quick. Heck in Ohio Winter may be here tomorrow, who knows.

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Unread 08-12-2013, 09:17 PM   #2
laybackman
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Quote:
Originally Posted by fourwheelnguy View Post
Hey guys, I need help again...

Background...I have a 1994 Wrangler with the 2.5L, 5 speed manual in it. Ran in until ~203k on the clock. New engine time came and I chose to stay with the 2.5L (yes I know some will chuckle) but honestly the four squirrels always did what I asked them to do, it was in my price range, and I was hoping it would be something fairly simple and would be heading back down the road. The last statement is anything but true.

Long story short it's been in the shop for the last two months, they can't get it to start on a regular basis, sometimes it will and sometimes it won't, doesn't appear to be any rhyme or reason to it. The shop has replaced nearly every electrical component on the Jeep, made new grounds, sanded the grounding spots, checked the entire harness out of the loom etc etc.

They are suggesting I may have a bad ECM (I had done the "brain" surgery on my ECM a couple years ago and it has worked great!) Anyways, I'm fortunate to have several Jeepers in the area that are willing to part with their ECM from when they did an engine swap and eliminated it.

My question is (and I searched through over 10 pages of posting before making this one as I don't want to waste anybody's time; so I apologize in advance if I missed it or didn't hit the right crawlers) does the part number on my, currently installed, ECM have to match the one I put in it? Before I purchase one from somebody I would like to make sure it will work... My ECM has a part number of 56028289, the dealer said the only ECM that would work would be this one or 56027575; is that true? Unfortunately those who have offered me an ECM don't have those part numbers.

As always your help and expertise is greatly appreciated!!! My wife may off me if I don't get her on any Jeep rides this Summer and it's coming to an end quick. Heck in Ohio Winter may be here tomorrow, who knows.
5602 7575 is the only ECM listed for your year/engine/tranny in a OEM parts manual. I can't find what the other number is for.
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Unread 08-12-2013, 09:32 PM   #3
Que89YJ
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Any 2.5 manual controller from a 91/95 xj or yj will work. Are you able to see codes when you cycle the key? When they say it won't start does the starter always torn over? Does the rail have fuel pressure to it? I can help you figure out what's going on if the ECU doesn't do the trick.
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Unread 08-13-2013, 06:38 AM   #4
fourwheelnguy
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Laybackman: If in not mistaking I believe 56027575 is the new number for 56028289.

Que89YJ: To my knowledge you can still see the codes when you cycle the key. I've had it to two shops to no avail. In between the two shops I tinkered with it for a couple days. During that time I was able to read the codes. The shop who currently has it is also able to hook up to the computer via a Snap-On diagnostic tool.

The starter always turns over, and I was told the CEL is cycling every time you turn the key over. When it doesn't start it wants to backfire through the exhaust. Sometimes it will start if you try again directly after that but it runs like crap. If it starts the first time it runs like a champ.

The rail has good fuel pressure and holds it. It's got a new fuel pump, pressure regulator etc. He has noided the injectors and all checks ok. He's also pulled the injectors and rail, primed the system and left them sit with cardboard under them to check for a leaking injector.

I guess my only concern was that I didn't want to buy a computer thinking it would work and if it doesn't fix the problem assume my issue is from something else when in fact I wasn't using a compatible computer.
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Unread 08-13-2013, 07:54 AM   #5
laybackman
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Quote:
Originally Posted by fourwheelnguy View Post
Laybackman: If in not mistaking I believe 56027575 is the new number for 56028289.

Que89YJ: To my knowledge you can still see the codes when you cycle the key. I've had it to two shops to no avail. In between the two shops I tinkered with it for a couple days. During that time I was able to read the codes. The shop who currently has it is also able to hook up to the computer via a Snap-On diagnostic tool.

The starter always turns over, and I was told the CEL is cycling every time you turn the key over. When it doesn't start it wants to backfire through the exhaust. Sometimes it will start if you try again directly after that but it runs like crap. If it starts the first time it runs like a champ.

The rail has good fuel pressure and holds it. It's got a new fuel pump, pressure regulator etc. He has noided the injectors and all checks ok. He's also pulled the injectors and rail, primed the system and left them sit with cardboard under them to check for a leaking injector.

I guess my only concern was that I didn't want to buy a computer thinking it would work and if it doesn't fix the problem assume my issue is from something else when in fact I wasn't using a compatible computer.
That wouldn't be the first time they did the ol' number change snafu...
I hate it when they print a document then go ahead and alter part numbers listed. It is a source document. Someone needs to get a couple of slaps behind the head at Chrysler.....Oh Yeah
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Unread 08-13-2013, 11:02 AM   #6
Que89YJ
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Do the ECU. If it doesn't do the trick try and get a list together and post back everything electrical that has been replaced. If there is backfiring at all it is a timing issue.
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Unread 08-13-2013, 12:38 PM   #7
fourwheelnguy
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Sounds good. I'm going to try and get hold of one and see what happens. As always, I appreciate the help and expertise.
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Unread 08-13-2013, 02:03 PM   #8
laybackman
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Timing issue.... One example I experienced when a timing issue wasn't timing issue, but a short to ground issue that acted like a timing issue.

My nephew had a '96 Chevy Blazer 4.3/auto. It would never start when it was raining out. It would turn over but not fire or pop back through the TB.

At other times it would start and run perfect. BUT later on that week it would fire up and run well then an hour later start to stumble and eventually cough, and die.

He had his friends that looked at it along with a few pros but they found nothing to cause this problem. It got parked.

Then he asked me for my help. I said OK but made no promises. In the back of my mind I'm thinking I'm getting sloppy 25ths at this so this is going to be bad.

But nothing was hacked up.

He had charged the battery so I popped the hood and he hit the ignition. It cranks but won't start. BUT.... I can just about here a spark arc somewhere under the hood.

So I tell him to cut the ignition and I start to 'investigate' The 4.3 has it's dizzy over on the passenger's side of the engine compartment. I find some tracing on the underside of a rubber hose in that area and I also find a small crack in his coil wire which is under this hose with more spark tracing on it.

While eyeballing this spot he hits the key again. Would you believe that the coil wire breach allowed arcing to this rubber hose!?!? Maybe because it was dirty?? I have no freaking idea but I saw it.

I slapped some electrical tape on the coil wire for a quick fix so he could replace that wire.

That 4.3 never did that again. He eventually replaced the wire. I will never assume that a plug wire cannot arc to ground via a rubber hose. Or should I say that a high voltage spark cannot dissipate onto a rubber item.

Listen..... & eyeball everything.
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Chicks dig me.....Fish fear me

Getting older, I have developed some special skills. I have the ability to cough, sneeze, fart and pee at the same time.

"If we cannot afford to take care of Veterans, then we should stop making them."
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Unread 08-13-2013, 09:18 PM   #9
fourwheelnguy
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Very good example! Thanks for sharing. I hate not fixing/ working on it myself, but I was hoping somebody other than me would have better luck, fresh set of eyes, and actually a mechanic!

I purchased a computer tonight from a '93 YJ, dropped it off to the guy and crossing my fingers for great news tomorrow!!!

I think the guy working on it now is about to pull his hair out, but he doesn't want me trailering it away from his shop.

Thanks again.
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Unread 08-14-2013, 11:41 AM   #10
Que89YJ
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Those hoses all have carbon and are conductive. Usually 8k resistance so they will act like a plug wire. If it backfires the firing would occur at random and fire through the throttlebody as well as the exhaust. I can think of a few good ideas but I will keep my fingers crossed for the ecu before I put in my .02. Check for codes after replacing the ecu and letting it run for 10 minutes and getting it into closed loop. If the problem comes back immeadiately check for codes.
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Unread 08-14-2013, 11:54 AM   #11
Siva283
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Time for another Que learning experience. There was another guy on her Rivera. His jeep would start up and shut right back off IIRC. It was his ECM we swapped ECM's and mine did the same with his ECM that his jeep would do and his ran great with my ECM.

Don't fret to much op Que and Layback will get you going I may even get a chance to chime in. Its almost always something easy and normally pretty cheap it just takes logical troubleshooting to get to it. This is just bad luck swapping the same engine in isn't always this bad. Eithier that or I got really lucky when I did mine. I had never swapped an engine before. Just get your Jeep back and follow the advice here and you will have it up and running in no time.
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[QUOTE=Magnum;14117863] I gave the Jeep the required offering of $$, sweat, and blood, and everything works fine now. -- Jim[/QUOTE]

[QUOTE=ldso;16498409]. It started with a $200 axle, and a few thousand dollars later I was done :)[/QUOTE]

[QUOTE=Luuca;16122017]diagnose the real issue before you start going all Obama on it - spending mad cash you'll need for other important things.

Ask me how I know...[/QUOTE]

[QUOTE=Overhead;17658665]this is also my second set of RC springs this year. I'd rather spend the money again and get something that will last.[/QUOTE]
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Unread 08-15-2013, 11:46 AM   #12
fourwheelnguy
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Thanks for the lessons!! Good to know that you're not always the only one with the problems!!! He threw the new ECM in yesterday and said it fired right up, but I'm still keeping my fingers crossed. He said he didn't get a chance to do anything else to it, or a chance to try it more than once etc etc, but I guess it's a good sign it turned right over. Now I just hope it continues to do that every time you want to start it and resolves all of the issues I was experiencing.

Siva - This was my first motor swap in a vehicle... I've done smaller things like waverunners, but not a vehicle. Kinda got down on my mechanical abilities...I like to tinker, but I'm not a mechanic by any means.

I really hope the ECM solves the issues...however, I stole the computer out of my Mother-In-Laws YJ about two months ago and tried it, but it didn't work. It turns out the remanned distributor that we put in that day too was incorrect so the Jeep would have never started anyways...I could type for pages about this and that; but bottom line I'm getting antsy to get her back home in MY garage where she belongs. I'll keep you guys updated; but I truly do appreciate all of your responses and help!!!!!
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Unread 08-15-2013, 05:30 PM   #13
laybackman
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Quote:
Originally Posted by fourwheelnguy View Post
Thanks for the lessons!! Good to know that you're not always the only one with the problems!!! He threw the new ECM in yesterday and said it fired right up, but I'm still keeping my fingers crossed. He said he didn't get a chance to do anything else to it, or a chance to try it more than once etc etc, but I guess it's a good sign it turned right over. Now I just hope it continues to do that every time you want to start it and resolves all of the issues I was experiencing.

Siva - This was my first motor swap in a vehicle... I've done smaller things like waverunners, but not a vehicle. Kinda got down on my mechanical abilities...I like to tinker, but I'm not a mechanic by any means.

I really hope the ECM solves the issues...however, I stole the computer out of my Mother-In-Laws YJ about two months ago and tried it, but it didn't work. It turns out the remanned distributor that we put in that day too was incorrect so the Jeep would have never started anyways...I could type for pages about this and that; but bottom line I'm getting antsy to get her back home in MY garage where she belongs. I'll keep you guys updated; but I truly do appreciate all of your responses and help!!!!!
Glad to hear it is alive!!
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Chicks dig me.....Fish fear me

Getting older, I have developed some special skills. I have the ability to cough, sneeze, fart and pee at the same time.

"If we cannot afford to take care of Veterans, then we should stop making them."
David C. Wilker Jr. USAF (RET)
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Unread 08-16-2013, 07:57 PM   #14
fourwheelnguy
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So here's the latest update...I spoke with, and made a visit to, the mechanic today. Unfortunately, he said it wasn't starting every time again. When I arrived he reached in, hit the key and it fired right up!! It reved up, idled great, sounded like you'd want a new motor to sound. He shut it off, we shot the breeze for about ten or fifteen minutes and he went over to start it again. Sure enough, wouldn't start. It doesn't do any loud backfires anymore, just a little bit of a rumble.

Here is where we are. He is going to tinker with it tomorrow for a little bit and he said if he figures it out he does and if not I think he's throwing the towel in. He said by the time he shuts down tomorrow I should have the Jeep, but may not be completely fixed. He said he's lost and doesn't know where to go really. (I've heard this guy doesn't give up on much from other's who have used him) Anyways, my hope is that he will have some epiphany tonight, and get it all figured out.

Quick question, I've seen my catalytic converter before as I put a clamp on muffler on it. My cat had been hollowed by the PO. I understand that noone is allowd to reccomend running the Jeep without one (I'm not asking for any of that, I use this forum too much to be banned!!) and I'm fine putting a new one on. But my question is can the cat being hollowed create a scenerio where there isn't enough back pressure? I never had a problem with the old motor starting, but was just wondering if something on the new motor may not be jiving with a hollowed cat?

I thought we had it figured out; looking forward to your responses, and thanks again!!!
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Unread 08-16-2013, 08:08 PM   #15
laybackman
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Quote:
Originally Posted by fourwheelnguy View Post
So here's the latest update...I spoke with, and made a visit to, the mechanic today. Unfortunately, he said it wasn't starting every time again. When I arrived he reached in, hit the key and it fired right up!! It reved up, idled great, sounded like you'd want a new motor to sound. He shut it off, we shot the breeze for about ten or fifteen minutes and he went over to start it again. Sure enough, wouldn't start. It doesn't do any loud backfires anymore, just a little bit of a rumble.

Here is where we are. He is going to tinker with it tomorrow for a little bit and he said if he figures it out he does and if not I think he's throwing the towel in. He said by the time he shuts down tomorrow I should have the Jeep, but may not be completely fixed. He said he's lost and doesn't know where to go really. (I've heard this guy doesn't give up on much from other's who have used him) Anyways, my hope is that he will have some epiphany tonight, and get it all figured out.

Quick question, I've seen my catalytic converter before as I put a clamp on muffler on it. My cat had been hollowed by the PO. I understand that noone is allowd to reccomend running the Jeep without one (I'm not asking for any of that, I use this forum too much to be banned!!) and I'm fine putting a new one on. But my question is can the cat being hollowed create a scenerio where there isn't enough back pressure? I never had a problem with the old motor starting, but was just wondering if something on the new motor may not be jiving with a hollowed cat?

I thought we had it figured out; looking forward to your responses, and thanks again!!!
If the cat was absent it would make no difference at all. It is what the sensor send to the ECM that counts.

Just for the heck of it. Take a jumper cable and attach it to the - battery post. Take the other end and scrape it along the frame where the hood latch is. Does it spark a lot? If it does your grounds are not good. Re-check the battery cable ground AND the second ground that goes from the firewall to the engine block.
Next I would remove and clean and lubricate the bulk head connector(s) and the connector for the ECM.
__________________
Chicks dig me.....Fish fear me

Getting older, I have developed some special skills. I have the ability to cough, sneeze, fart and pee at the same time.

"If we cannot afford to take care of Veterans, then we should stop making them."
David C. Wilker Jr. USAF (RET)
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