Help! Changing na/auto 87 targa to turbo/5-speed. Bought a jdm engine&trans from Canada and got burned badly, but latest issue is turbo wiring harness is way to short to reach the firewall hole for ecu hookup. Wtf? Do I have to cut and splice, or is there a better way? Also, what are the small heat sink type boxes on both fender wells? Thanks for any help.
Engine swap new harness too short
- Thread starter rustfarmer
- Start date
One of the heat sinked boxes is a fuel pump resistor and the other IIRC is the head light resistor. Dont hold me to it as i havent had those on my car for years. Have you looked them up on the TSRM or EPC?
http://www.cygnusx1.net/Supra/Library/TSRM/MK3/default.aspx
http://www.cygnusx1.net/Supra/Library/TSRM/MK3/default.aspx
Buy a new harness.
The JDM engine sits in a RHD car and the glove compartment and therefore the ECU is in the left hand side of the car.
The harness is therefor shorter on a JDM engine.
So new harness or splice.
The JDM engine sits in a RHD car and the glove compartment and therefore the ECU is in the left hand side of the car.
The harness is therefor shorter on a JDM engine.
So new harness or splice.
Thanks very much for the info. I wondered if this might be the case, as the heater hose hook-up also seemed backwards. If I hook heater hoses up reversed, will I have hot water in the heater core all summer when trying to cool? Thanks again, RF
rustfarmer;1436761 said:
Just did this job. Even with a new harness, there is a lot of rewrapping, soldering or crimping (if you have to right tools to do it nice), replacing some wires, etc. This is to make any harness reliable again after 20 years. If you extend the harness it is a lot more work than it looks, prone to error, and definitely not worth it, IMHO.
Also, get a harness as close to the body style of the receiving car, engine type, and trans type as possible. If you have an 89 its dicey, because there were changes throughout that model year. It is critical that the ECU and Harness match, preferably from the same car. If not check all the connectors, starting with those to the ECU.
I didn't run into heater line problems because I used the piping from the original motor, not the JDM. If you go backwards - you're kidding about cooling and heat being mixed up, right? That wouldn't happen. IDK if the coolant could run in reverse, but I can imagine lots of ways it might not work and make a mess. Why not run a longer hose and get the direction right?
Victor Charlie;1437275 said:
Ok and thanks for the info. I didn't mean heat and cooling mixed, but just that if the cut off valve is on the exit side of heater core instead of entrance I would expect hotter water to be in the core even when shut off. You are right, however, I just plumb the thing correctly and feel kinda dumb for not noticing this before installing the engine.
As for ecu, the one that came with the engine has an extra 4th plug on the side of box with wires that run around the exterior and then enter the ecu at what looks like a factory entrance point on the back. The harness that came with this jdm engine has the usual three plugs which fit the ecu ok, but also has another 3 wire plug not found on the old automatic harness. Is this likely the plug for the clutch pedal no start switch, and if so, how do I simply jumper it. I don' care if it will crank with the clutch out and in gear as this can sometimes be quite useful.
Thanks again. Can't believe how great you forum guys are to a sometimes dumb old fart.
rustfarmer;1437643 said:
I'm about the least experienced guy on the forum, so take what I say with a grain of salt. i just answer the questions that I'm pretty sure of to take the pressure off the smart guys. I have no idea about your ecu, haven't seen any talk about it, but that doesn't mean anything. You can jumper the clutch pedal at the switch under the dash. Definitely get to know the electrical wiring diagram online. it shows the circuit the switch is in. It simply opens the circuit triggering the starter relay, so no harm if it is always jumpered. All the manuals and parts catalog are here:
http://www.cygnusx1.net/Supra/Library/TSRM/MK3/default.aspx
maybe try cutting a hole through the firewall near the speedo and feed it through there, or find a place in the engine bay and extend the body plugs....hth
boostindoo;1438249 said:
??? Just get the right pipe, plumb it right. It's not expensive, its not too time consuming. Why hack up a perfectly good supra?
If you do decide to extend your harness, cut and extend the wires one at a time to be sure you dont mix them up. Use stranded wire. On old wires such as these using flux would be a good idea.
see post #6 in this thread, OP was talking about a related problem with the heater hoses in motors from RHD cars going in LHD chasis. I thought you were referring to that post, sorry for the confusion.
I still really think you guys should get the right harness, having just finished working out the same problem myself. I was itching to start cutting and soldering and extending the JDM harness, and I was really glad I waited a week for the right harness to come in. They are pretty cheap used, and even if you work at MickyD's. I'm not a great mechanic, but I'm good with electrical stuff and soldering. IMHO it's not cost effective to spend your time fussing with the wrong harness for a bunch of reasons that tend to crop up as you put the car back together. If you really want to do it, I've seen posters who have done it on one of the supra forums, search and you'll find pictures of the job.
I still really think you guys should get the right harness, having just finished working out the same problem myself. I was itching to start cutting and soldering and extending the JDM harness, and I was really glad I waited a week for the right harness to come in. They are pretty cheap used, and even if you work at MickyD's. I'm not a great mechanic, but I'm good with electrical stuff and soldering. IMHO it's not cost effective to spend your time fussing with the wrong harness for a bunch of reasons that tend to crop up as you put the car back together. If you really want to do it, I've seen posters who have done it on one of the supra forums, search and you'll find pictures of the job.
if u really, really have to extend it, stagger the wires and do them one at a time. definitely use flux. but yeah, get the right wiring harness.....
Thanks for all the input guys. Done a lot of rewires over the years so guess I might as well give it a shot. I'm bet your right about cost vs time but at the moment time is cheap. I'll take pics for anyone who wants and post them in my album at rustfarmer's photos.