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EJ swap noob questions


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7 replies to this topic

#1 rxleone

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Posted 09 May 2012 - 05:07 AM

I've recently picked up a EA82T GL-10 with a 3AT in it (badged as a Leone GT-AT, JDM) but the engines pretty buggered and I've wanted to do an EJ swap for a long time. Been on the USMB for a few years now, watched builds and I'm quite excited and motivated to do it. Thinking about a JDM EJ20D from an 89-93 model Legacy with a 5sp D/R. I know you guys didn't get the early DOHC engines, so don't worry about that.

I'm not worried about the gearbox swap, I figure that'll be the easy part, along with the mechanical side of the EJ swap. I'm just wondering about the harness stripping.

I find the EA2EJ swap guide pretty informing, but there's a lot of grey area with the whole stripping the harness side of things. What's the best way to go about it?

I've seen a lot of people sort of say "just identify the parts you need and strip everything out" but how do you identify that you need? From what i gather you need, crank/cam sensors, water/oil/knock/air sensors, fuel pump relay, etc. Do you basically strip everything that doesn't come out of the ECU-side plug?

In short, is there some sort of "idiots guide to stripping harnesses" I can use? I'm really keen to do this and I know the learning curve will be steep. I just want to know what I'm letting myself in for with the wiring side of things.

#2 LPGsuperchargedBrumby

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Posted 09 May 2012 - 06:34 AM

check that the DOHC ej will fit between the frame rails....

i know the EA82 chassis is wider than the EA81 ones i'm used to but the DOHC donk is a pretty wide motor across the belt covers

lol a SOHC EJ will drop in like its meant to be there

#3 Gloyale

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Posted 09 May 2012 - 11:11 AM

I find the EA2EJ swap guide pretty informing, but there's a lot of grey area with the whole stripping the harness side of things. What's the best way to go about it?

I've seen a lot of people sort of say "just identify the parts you need and strip everything out" but how do you identify that you need? From what i gather you need, crank/cam sensors, water/oil/knock/air sensors, fuel pump relay, etc. Do you basically strip everything that doesn't come out of the ECU-side plug?


a few main engine connectors, the transistor, and the MAF plugs. That's all your gonna need from the engine bay. trace back between those connecotor and the ECU.

You'll never figure it all out in your head now. Just get the whole harness out, and start stripping off wiring....there will be a moment where you go "AAAAHHHHHHHGGGGGHHHHHH!" and feel overwhelmed, keep working.....and eventually you'll start to make sense of it.

#4 El Presidente

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Posted 09 May 2012 - 03:34 PM

I just stripped two obd1 harnesses and I couldn't find any good writeups or threads that helped much. Yes, a lot of responses are just "strip everything you dont need", which is very vague considering most people don't know what they need! Even finding a strategy to get started with is tough. I was able to get the help of another board member to help me out and things went much easier, if you can do this, do it. If you can't, don't sweat it.

First, strategy...start at the plug ends and not at the ecu end of the harness, you'll work from the ecu end once all the extra stuff is gone.

Identify all plugs needed by plugging them into the motor. Depending on the year, you'll have two or three engine harness plugs, these are light grey and square..don't confuse them with plugs for an auto tranny, if it came with one..they look very similair, but a majority will go back to the TCU. The harness for the Maf is the longest and there is another group for the O2 sensor, and the tps and aic(i think). If IRCC theres only like 5 plugs you need. There are some exeptions to "cut out everything that doesn't plug in" things like the fuel pump and ignition relay(which is mounted together on a little plate), on a abd1 i'd leave the check connectors and I also left my SSM(Subaru Select Monitor..Subaru's obd1 diagnostic port), If its obd2, leave the obd2 port.

Start cutting, if its unidentified, you don't need it, because you've already isolated everything you do need. I found it easier to just cut the connectors off and leave the wire in the harness, once you have all the connectors cut you don't need, pulling the wire is easy and will come out by the handfuls. I always cut an inch or two from the connector so if I make a mistake, I have something to solder onto. Do not cut the shielded wire, they are for critical sensors and very voltage sensitive

Once you have all unnecessary wires in the harness out, you'll realize there are cut wires going to the ECU...don't panic...these are for things like power to the ecu, grounds, VSS sensor(which is in your car already behind the instrument cluster), check engine light, starter, etc. This is the point when you work from the ecu end. Get a pin out of the ecu(its in numbchux ej writeup) and identify every cut wire and give it what it needs, there may be some that stay cut so don't be alarmed. Once you do one, the next one is a breaze..my second harness took 2 hours to strip from still wrapped in tape. My experiences are based on obd1, so yours will be different, but much of what I said should apply. Good luck

Josh

#5 rxleone

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Posted 10 May 2012 - 12:44 AM

I'm fairly sure the early JDM EJ20D is OBD1, which is good news. So basically what you're saying is to cut the plugs off the end of anything that isn't related directly to the ECU, bar the Fuel Pump relay and the Ignition relay, the dash meters, and the diagnostic plugs?

Also, if I swap a dual range box in, how do I wire the neutral switch? And do I wire it to the clutch pedal or the gearstick?

#6 WoodsWagon

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Posted 10 May 2012 - 03:55 AM

The clutch switch input is more important to the ECU to prevent stalling when coasting up to a stop. It cuts all fuel injection when coasting, the clutch switch warns it to start fueling the engine again because you're about to de-couple it from the wheels. I don't think I ever hooked up the neutral switch on the transmission because some of my d/r's were from carbed cars and others were from EFI so it was a crapshoot if it would have the switch or not.

I went though a lot of transmissions.

#7 Numbchux

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Posted 10 May 2012 - 09:35 AM

Start cutting, if its unidentified, you don't need it, because you've already isolated everything you do need. I found it easier to just cut the connectors off and leave the wire in the harness, once you have all the connectors cut you don't need, pulling the wire is easy and will come out by the handfuls. Do not cut the shielded wire, they are for critical sensors and very voltage sensitive


I really don't recommend this. I think it's absolutely worth the time to trace every wire through the harness and get rid of it. If it goes to a plug that you know you need, identify it and label it.


Also, the ABS system uses some shielded wires.....you don't have to save those :D

But yea, be careful around the crank and cam sensor wires. Those can cause problems.

#8 Uberoo

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Posted 12 May 2012 - 12:33 PM

when you are pulling the harness itself from the car cut connectors that you KNOW you will not need.Lights,heater fan,wipers, cruise control(unless you want cruise control) etc.When you have the dash off the car you will see that the harness splits in the middle of the car.One bundle of wires goes through the firewall DO NOT CUT THESE WIRES.The other bundle heads over to the passenger side of the car and from there it goes and feeds into stuff like taillights,seatbelts,power windows..there is only ONE wire from there that you will need.Its a black wire with a red tracer, it goes to the fuel pump from the fuel pump relay.However you can cut that whole bundle of wires.It might be worthwhile to keep the fuse box in the harness for as long as possible to help figure out where power needs to be. take the time to unbolt any grounds you come across.Many will just fall out of the harness after you remove a few wires. the ignition relay needs a ground,but you wont know which wire that is until you can trace it to the ignition relay.The connector that goes to the instrument cluster can be cut although a few wires a needed and those go the ecu.these are things like check engine light,tach,vss,etc. You can also remove all the other relays from the ej car other than the ignition relay and the fuel pump relay.Those are relays are for things like headlights,wipers,turn signals.Stuff that isn't needed because the car you are putting the engine into will have all those and those relays arnt needed to make the engine run.
Are you running air conditioning?if not cut the connectors to the AC related stuff.Are you running an auto or a manual transmission?If your running a manual and the donor car came with an automatic you can cut all the wires under the hood leading to the transmission, same with the wires leading to the TCM, its the gold box under the dash.the engine ECU is the silver box with yellow connectors..

that should get you started.Once you get the harness home take the tape off and start tracing and removing wires that were cut when you removed the harness.

just keep track of the powers.My own EJ swap wouldn't start for a while because I didn't have power where it was needed.Once I added those power wires the engine started up and idled smoothly,Even if it did SHOUT that it was alive.Y pipe only is pretty loud in a garage..

hope that helps.




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