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[turbostd]

Im helping a guy finish a motor swap in a jeep. The first guy working on it bailed on him and left the job half done so I was recruited to finish it up. We got everything bolted together and hooked up after a lot of searching for bolts etc. (it had been apart for ~4mo) Anyhow we get it all done and ready to start up and the ecu wont power up for some reason. I am not familiar with the later model jeep 4.0 but some internet research lead me to suspect the cps sensor. We put a new one in and still nothing. If this where a honda I would suspect the main relay was bad but its not. So far we have ruled out all the fuses, the relays and the grounds. Last thing on the list is the ecu itself but its like $500 and you have to bring the jeep to a dealer to get it programmed.

Any ideas why this thing wont power up? Anything obvious I am missing? The ecu gets power, the gauges do not work, the cel does not come on nor does the fuel pump, there is no spark or power at any sensor plugs.

[Joseph Davis]

Some of those have an immobilizer, IDK the details of how it works.

[chris]

If it was a honda i would say thermosat ground

[Joseph Davis]

If it was a honda i would say thermosat ground

Yeah, sensor and/or power ground.  No cluster lights can be an IMMO issue, but everything else "should" come on line to the best of my knowledge.  Jay should know best, honestly.

[turbostd]

Well, the guy had this thing towed to my house so I can actually work on it more now. So far I have verified the ecu gets power and ground where it should but for whatever reason it still wont start up and send power out to anything. I double checked all fuses and relays. I unplugged every sensor that uses a 5v reference and it still did nothing. At this point I am pretty sure its a bad ecu.

[Joseph Davis]

ASD?

[turbostd]

as far as I know if it was the asd the cel should still come on and it would start but shut down in a few sec.

[CSaddict]

Did you try starting it in Neutral? NSS are always bad on those.

[turbostd]

NSS seems fine but i did try it in N and it still did not work. I am out of ideas at this point and I hate to just throw parts at it but I am at a loss. I guess we can throw an ecm at it and if it still dosnt work we could just resell it and try something else. I have tried everything any one suggested and everything I have found in posts online and its still dead.

[Joseph Davis]

I have a 1996 Jeep Cherokee Sport 4.0 ECU I can (insert broken sobbing here) attempt to drop in a box and (insert unstable gibbering laughter) ship to you tomorrow.  I think it's AT and I have no idea if it's an immobilizer affair.  PM me your address, Paypal shipping plus 3.3% when I shoot you a pic of the USPS receipt, if it works kick me enough for a pint of rotgut liquor, if it doesn't work try to give it to someone it might work for.  FUCK YOU

[darkelvis]

I would take JD up on the ecu offer....those fuckers have MAJOR ecu problems....I've replaced 5 (or so) of them in the last year at work....and what you are describing sounds about right.