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Old 08-10-2010, 06:16 AM   #1
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Default Electrical Problems - No EFI

Hi all.
Been here alot to generally find help on all my problems but I cannot seem to find the answers anywhere so I am posting. Hopefully someone can help.

First of all my car is a JZA80 Supra MkIV 1994 with a 2JZ-GTE in it.

Just did a rebuild (bottom end, left heads on), and I cannot get the car to start. It cranks fine, but I do not hear the EFI relays or fuel pump when I first turn the key. Also no check engine light.

And I have plugged in ECU and most things ect... Though I might have missed somthing so feel free to point out the obvious.

Here are 2 things that may have had an impact.

1. Shorted the imobilser/alarm (mongoose M80). I replaced the fuse that blew and now the doors and started and fuel pump cut off function normally. I may have missed another fuse?
2. Shorted the +'ve battery terminal to earth briefly when doing up the battery strap (knew I should have been more careful, but I was excited to get my car going again ) Did not find a blown fuse.

Things I have tested.

Fuel pump -> jumped it with a battery and it runs.
Fuel pump ecu -> tested power comming in. No volts on the main power. do have 12 volts on the fuel gauge.

Checked all main fuses (all of them) and relays (EFI main and EFI 2) (main fuse box in the engine bay).
No power to EFI relays on the resistor side. There is power from the +'ve fuse terminal in the fuse box itself.
Checked earth from +'ve fuse terminal to engine and to chassis and get 12v

Thats as far as I have gotten so far.

I do plan to
: check the power to the EFI fuse
: check the power to the ECU input

I also want to check the 7.5A IGN fuse that is in the wiring diagram, but I can't for the life of me find it. Checked under the steering colum and kick well of the driver, So if someone could give me a general location that would be great.

I am still a bit suspicious of the imobilser cutting the power to the ECU.

I am aware that I still have to do some more testing before I can find the exact problem but if anyone has had these problems before and can give me some more things to test or simple things to check would be great.

Thanking you in advance for your help!

Last edited by Sapar; 08-11-2010 at 05:27 AM.
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Old 08-12-2010, 04:13 AM   #2
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Default Testing stage 2

Ok I have found that I do not have the 12v power from Ignition switch to ECU. I do have power from other pins.

I have checked the power from the 7.5A IGN fuse in the drivers foot well and I am getting 12 Volts there.

Somehow I lose the power in the transition from the IGN fuse to the ECU and I am leaning towards the Immobilizer as the culprit.

Studding a the wiring diagram a bit more, but if someone has done immobilizers before on a supra, where do you splice into the Ignition wire? I can't seem to find anything so far.
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Old 08-12-2010, 07:09 AM   #3
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Default Power at Igniter

Just checked the power at the igniter as it gets its power from the Ignition switch. I have 12v at the noise filter and the Black and Orange wires on both A and B igniter.

So I am getting power from Ignition 2 switch from the key. (as proved by having 12v at the 7.5A IGN fuse.)

Now my Diagram says that the power goes like this.

Battery -> 30 Amp fuse (Checked) -> Ignition SW -> IG2 position -> I20 Junction (no idea where that is) -> splits to igniter (has power) / splits to 7.5A IGN fuse (has power) -> Then somehow into ECU which is the other side of the car, but also being part of the engine wiring harness. I think it hooks up on the igniter plugs. to ECU A-plug at position 1 (no power)

I am convinced that this is my problem. Somehow I do not have power from the fuse to the ECU.

One interesting thing to note is that with the -'ve terminal off the battery, I have 12V from Resister activator side or EFI Main relay to -'ve Battery Terminal. While I cannot get the 12v at position 1 on relay with the battery connected and the keys on.

Is this something note worthy? Did I forget to reinstall a ground? Or am I grounding the wire somewhere where it should not be?

I allways have 12v from 3 on the main relay.

Anyways I am getting reads but no one seems to know whats going on.
Hoping someone can through me some ideas!

Last edited by Sapar; 08-12-2010 at 07:29 AM. Reason: more info
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Old 08-12-2010, 08:22 AM   #4
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Default Found problem area

I had found junction II1 (big orange plug that goes near the ECU), I could not use the search function in the PDF manual to found it and I sort of stumbled onto it.

Located it in my car, unplugged it and turn my car to on (I switched the immobilize). Ran a multimeter onto the input wire from the 7.5A and I had 0 volts. So somewhere along the way I had lost the signal from one side of the car to the other.

I only had one other power as well, but I am assuming they get their power from relays ect that I cannot power up cause I am missing the IGSW signal.

I am not sure how I am not getting power at the moment, as there is no more fuses/splices from one point to the other. Maybe I am back to the immobilizer being at fault, as I did short it out way back at the begging of this problem.

Once again would appreciate anyone's help on general splice locations for the IGSW single for immobilizers (somewhere after the Fuse but before the orange junction plug) as it was a really good job on the immobilizer install. the box itself hidden well, and the wires are soldered and capped, and covered well back to mask the presence of the wires.

Hoping someone can help me out!

I am tempted just to splice the BATT and IGSW together at the moment... Or run a wire from the fuse and splice that directly into the ECU plug
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Old 08-14-2010, 05:59 AM   #5
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Default Fixed it

I fixed it!

I just ran a wire from a gutted fuse in the IGN fuse to a fuse holder and then directly to the IGN wire to the ECU.

It must have been damaged somehow.

Now I have a funny ticking noise, and it bogs down every now again.

I think the bogging down is from fouled plugs. I did have the engine upside down for 2 weeks, so oil could have got to them.

I will work out the ticking noise, could be the little guide washer that goes to the gear box, or it could be an imbalance on the crank, since I changed the conrod bolts.

Anyways That's the end of my not starting problems. No one posted but then again I sorted it myself anyways. Maybe next time?

Have a good one!
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Old 08-14-2010, 04:02 PM   #6
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Thumbs up Congratulations

Wow - glad you got it fixed!

Many thanks for posting your troubleshooting steps and your solution.

Please pardon my delayed viewing of your posts - I had been away on business travel.
Phil '94 Supra Turbo, 6spd, 'APU'+
Displacement is no replacement for boost.
Life begins at 30psi.

NB: Please consider posting any help requests in a new thread instead of asking me for help privately. About 99.9+% of the time, private help requests end up covering great information that could be very valuable to other forum members. If you have a good reason for needing the help request to be private, I'll consider it. If not, then why not give everyone else the opportunity to pitch in too, and/or learn from the information? Remember, there's no such thing as a dumb question. We're all here to help within this family of Supra owners.
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Old 08-16-2010, 09:33 AM   #7
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Default No Problems

Thank you for you comments. Maybe someone else will have the same thing and it can help them out.

On a side note all the manuals I used for the rebuild and diagnosing can be found here


click download and it has ALL the manuals for the Supra MKIV, I know it says 1997 but they are all pretty similar. Its also the American Left hand drive. But it has units in both metric and imperial.

Good manuals deffinatly worth having. Might have been mentioned before but if someone does read this and they start wondering how I knew what went where, I got it all from here
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ecu, efi, fuel pump, starting

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