Need assistance determining what a wire is for

[vaboy]

I'm brand new here, this is my first post. I didn't start out in the introduction section because I have yet to purchase the car. The car is an 86.5 7mge 5 speed manual with 90k miles. I'm looking at purchasing it from a friend who can't get it running correctly. He currently has it hotwired, he added a wire from a wire receiving power to an orange wire with a black stripe that is located behind the battery. my hopes is figuring out what said wire is for and replacing it upon purchase or hoping it leads me to the problem, bad part good wire perhaps. If anyone knows what said wires purpose is, or has an electrical diagram with said wire they wouldn't mind sharing it would be most appreciated. He is also going to allow me to pull check engine light codes off the engine, I've found what the codes mean for a turbo'd ecu but can't find any for the 86.5 nonturbo. if anyone can help at all I would be most appreciative and I look forward to becoming a fellow supra owner. Thanks for your time

 

[jetjock]

http://www.cygnusx1.net/Supra/Library/TEWD/MK3/


Don't see an orange/black but black/orange is power for the injectors and ignition coil. Also used to fire up the ECU:

http://www.cygnusx1.net/Supra/Library/TEWD/MK3/manual.aspx?S=Main&P=54


Codes for both engines:

http://www.cygnusx1.net/Supra/TechTips/engine_error_codes.aspx

 

[vaboy]

Wow I am beyond grateful for your help. Thanks so much. Now I just hope I can get it running correctly

 

[super51fan]

If the car is hacked up in lots of areas i would look for a different car. It will be much easier and probaly alot less money to start with a unmolested platform from the get go. I saw the Mach 5 supra for sale in the general section. You could start with this car. Just kidding!!!! Don't be in a hurry to get your "supra". Spend some time to find the nicest staring point you can. Try to find one that has not been hacked on. You are basically buying someones problem that they could not make work. Nice 91 white with maroon leather in sale section with sunroof that needs an engine. Priced high at $4500 but at least it needs one thing. An engine. Not staring with a butchered wiring harness then get it running to find out engine is bad. Then how is the body, interior? Good luck with what ever you do.

 

[vaboy]

So i went back and check out the car again and got an update with dome correct information. There is a wire connecting a black wire with orange stripe(I presume ignition wire from my Haynes manual) to a black wire with a red stripe(fuel pump related wire also Haynes manual). The fuel pump has been replaced along with the filter. When these two wires are hot wired together it will start right up and run fine but when you turn the key off the car does not shut off. When the wires are not connected the car will only crank over and over. I'm hoping someone could help me out with what faulty part is being bypassed in order to create this continuous closed circuit or if it sounds like a bad wire(short perhaps). The person I bought it off of said he checked the fuel pump relay and it was good. I'm stumped. I appreciate any and all help. Thanks.

 

[jetjock]

For the engine to not shut off with the key both fuel and ignition would have to be hot wired. The first thing you should do is throw that Haynes manual in the trash and stick with factory documentation. Rather than try and figure out what's wrong with the wiring it's often easier to just return it to stock. Use the TEWD for that. All the information you need is there. If you have trouble interpreting any of it I or someone else here will explain.

 

[vaboy]

I'm really only using the Haynes for the wiring diagrams. Are they going to be wrong for wire colors? It's just hard to connect the drawings from the website. I am going to try and get colored print offs but until then it's strictly smartphone..

 

[vaboy]

I took a couple picture of where the solid red wire splices onto the black/orange, and the black/red. don't know if it helps..

 

[jetjock]

Yeah, that right hand pic is a connection to the fuel pump circuit. Disconnect it and use the diagrams to find the real problem. Why not just buy a TEWD for that model year? They're not expensive.

 

[Dirgle]

First, I would like to reiterate what Jetjock said.Throw the Haynes in the trash! That book is one of the single greatest pieces of misinformation, inaccuracy, and blatant laziness ever put to print. I'm sorry if you paid cash to get it, consider it an unfortunate, and costly lesson, and move on.

Secondly, I think he is bypassing EFI Main relay. He is pulling power from the injector circuit(B-O) and passing it to the EFI Main relay output(B-R). This is all powered by the IG2 ignition switch output.

This bypass works the opposite way when you turn the ignition switch off. Since the ign input for the ECU is also powered off of IG2 it gets powered by the EFI Main relay once it is active keeping the ECU on after the ignition switch is turned off.

 

[vaboy]

I honestly didn't know they sold them, thought it was kind of an online database kind of thing since all I've seen it referred to as was the websites. that's bad researching on my behalf. I will defiantly be purchasing one. So then in theory I have a bad EFI Main Relay that he bypassed to get the car running. Well that shouldn't be to bad to replace. I appreciate the help, I'll replace it asap and get back with everyone on if that solved the problem! Thanks again!!

 

[Dirgle]

In theory no, I don't believe the EFI main relay is bad. If it was, the the car wouldn't be able to operate after the key was turned off. If you can get your hands on a multi-meter, it would be better to troubleshoot rather than throw parts at it.

 

[vaboy]

But if they did bypass that relay and the car won't start without that connecting wire but with the hot wired set up will start but not cut off with the wire then wouldn't that relay be the most likely cause. The relay isn't there to stop the fuel system causing it to stay on? Got a multi meter l'll start digging around next chance I get. I'm just not 100% on what to check at this point. Never really had a problem like this on any vehicle.

 

[Dirgle]

The reason I suspect that the EFI Main Relay is still functioning is because you stated even if you turn the ignition off the engine continues to run. The only way this can happen is if unswitched power is still coming across the EFI Main Relay. To do this the EFI main relay must be working. The questionable jumper wire then routes power back onto the Injector power line, which which is connected to the IGN wire which tells the ECU to stay on. This is the only way I can see that the engine would continue running with the wires you showed us and the ignition turned off.

The operation of the EFI main relay can be checked with the ignition in the ON position, by looking for +12v at the +B pin inside the DIAG connector in the engine bay. Also look to see if the previous owner placed a jumper wire inside the DIAG connector between +B and FP.

 

[vaboy]

That makes sense. good explanation. We're going to test the relay tomorrow evening just to be safe. It's really starting to sound like a bad wire somewhere if we can rule out the EFI Main relay. Bypasssing the EFI Main relay explains why it won't shut off but not what the actual problem is with it not starting. Unless I am completely missing something. If it is a short it seems like it would be between the Circuit Opening Relay and the EFI Main Relay at least that's what I'm making of all this.

 

[Dirgle]

You should definitely troubleshoot the system. We're still missing something though, based on the information at hand I can't explain why the engine would start with the jumper wire but not without it. I have some ideas but nothing I can backup.

Remove the jumper wire and test:

At DIAG connector
W/IGN on check for 12v at +B
If good move to COR for testing
If bad move to EFI Main Relay

EFI Main Relay
Pull the relay and with the IGN on:
Check for 12v in the connector on pin 1. If bad check the 7.5A IGN fuse.
Check for 12v in the connector on pin 4. If bad check the 15A EFI fuse.
Check for continuity to ground in the connector on pin 3. If bad check ground point 'C'.http://www.cygnusx1.net/Supra/Library/TEWD/MK3/manual.aspx?S=Main&P=151
Test the relay as per TSRM: http://www.cygnusx1.net/Supra/Library/TSRM/MK3/manual.aspx?Section=FI&P=109

COR:
Test as per the TSRM:http://www.cygnusx1.net/Supra/Library/TSRM/MK3/manual.aspx?Section=FI&P=110

 

[jetjock]

Listen to Dirgle. The man knows of what he speaks. Again, remove whatever wiring isn't stock and then, using the EWD, simply troubleshoot and repair whatever is causing the problem.

 

[vaboy]

I really do appreciate all the help guys. If I stumble across the problem I'll defiantly let everyone know what it is. You again you guy were a tremendous help. I look forward to getting this fixed so I can enjoy supramania and learn more about my new vehicle. Thanks again

 

[vaboy]

So I checked everything that was said to check(after removing the jumper wire in all cases). All I came up with was that with the ignition Off pin 4 is showing 12v. it shows 12v regardless of ignition on or off. Both relays checked out and there is good continuity with the ground. in other news I see they had a very off way of pulling power off the positive battery terminal... I worry about whoever owned this car before me.

 

[Dirgle]

I assume you are talking about the EFI Main Relay. Pin 4 goes to the EFI fuse, which is unswitched and should always have 12v going to it, even with the ignition off.
http://www.cygnusx1.net/Supra/Library/TEWD/MK3/manual.aspx?S=Main&P=036

The next step I would take is to check with the ignition switch on, and the jumper wire removed, see if there is 12v on the Black/Orange wire that the jumper wire went to.

As for that other wire, that is just plain scary. Where does it go? It looks like a white wire, if so it is probably the primary power wire for the fuse box in the engine compartment.