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sasquatch1970 04-09-2013 01:43 AM

xj ECM modifications and retrofit into a 1938 Plymouth
We took the engine and harness out of a wrecked 1991 xj 2wd. We installed the 4.0L engine and automatic transmission and rear end in a 1938 Plymouth sedan. I have wired up a aftermarket harness for the car but need to know if anyone knows what wires I need to keep for the ECM to run the fuel injection,etc. and make the engine run.... We also are trying to get the programming out of the ECM for the anti theft security... any help would be great. Also if anyone knows if I can ditch most of the power distribution center to lighten the harness and what relays I need to keep?

We have two Chrysler service manuals for the jeep and chassis so I can reference the pin numbers if someone knows what I need to remove and what I have to leave..... This is a nice upgrade for the old 38 and we are mopar folks so we are keeping it mopar... I will post up some photos when I get it done..... It is a jeep in sheep's clothing,,,, Thanks

cruiser54 04-09-2013 07:44 AM

Cool project!!

Diamond-x 04-09-2013 12:32 PM

First, I have not done this swap. Nor have I seen anyone else having done this.

I would imagine it would be easiest to swap the entire harness over, including the power distribution. It has relays for the fuel pump, etc, that are crucial to the engine running. The main harness connection to the dash, through the firewall, will be the biggest concern. You'll need the service manual to figure where the wires will interface to the ignition, power and others.

Sounds like an awesome project!

Please post pictures!

sasquatch1970 04-10-2013 09:45 PM

4 Attachment(s)
Diamond X

I agree that using the whole harness would have been easier, my buddy cut off the engine portion of the harness and scrapped the rest. He bought a aftermarket hot rod wiring harness that I already wired up so now I have to figure out how to integrate both harnesses enough to make it run. His 4.0L engine only has 50,000 miles on it so it should run sweet in the 38 Sedan. Talking with the Chrysler dealer today they said that if the ECM has security which ours does, we have to get a new ECM that doesn't have security because you cannot un program it out of the ECM.

what I REALLY need help with now is seeing what wires I need to keep to the ECM to make it run when you hit the key. I know I can eliminate the wires for the idiot lights and airbag stuff and anti lock brakes since we dont have any of that anymore, but trying to figure out what we HAVE to have is interesting because as of now I don't know of anybody doing this kind of swap before... If it was easy then everyone would be doing it....

TDTech 04-10-2013 11:23 PM

cam sensor, crank sensor, map sensor, coolant temp sensor, o2 sensor. that's all i can think of at the moment. those need to be hooked up for it to run the way it should. it'll run without the coolant and o2 sensor but it will run real rich.

Kalali 04-11-2013 07:06 AM

Take that orange filter off that motor before you get too much flak...What you need is the wiring diagram. I'm sure someone here has it. Or get the FSM.

cruiser54 04-11-2013 07:14 AM


Originally Posted by Kalali (Post 15279974)
Take that orange filter off that motor before you get too much flak...What you need is the wiring diagram. I'm sure someone here has it. Or get the FSM.

Were you referring to me? About the flak, I mean. LOL.

Diamond-x 04-11-2013 11:57 AM

You'll save a lot of time by starting with a non-security ECM and a complete harness, unplugged, not cut.

Paint looks nice!

buildin1XJ 04-11-2013 12:29 PM

Cool Project. With the cut wiring harness how do you plan to wire the Transmission control module?

The time now is 05:06 AM.

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