After a long series of diagnostics on my 86.5 I have discovered that the probable cause for why I'm not getting any spark is that somewhere in my wiring harness there is a problem with getting juice to the distributer. I have no power to the M-REL, or between terminal +B and body ground. I got to the ECU with a voltmeter and started testing things as per the TSRM, but I've come to the point where all it tells me to do now is check the wiring harness. Has anybody else had this problem? And is there a way for me to determine which wires need replacing and where? or should I just look for a completely new wiring harness(where? all ebay has are turbo harnesses) If anyone can offer advice or point me in the direction of a thread that addresses this problem I would greatly appreciate it. I have a friend who is a toyota mechanic, but he says he isn't particularly skilled at electrical diagnosis, so if somebody can help us get past this roadblock hopefully I can get my car running!
Wiring Harness Diagnosis...Repair/Replace?
- Thread starter kwutzo
- Start date
kwutzo;1031968 said:
I don't have an 86.5 diagram, but will use the online 89 version.
Since your 86.5 can't be that different from the later, you don't have power to the distributor. It generates a signal on its own. Uless you are talking about spark from the coil.
http://www.cygnusx1.net/Supra/Library/TEWD/MK3/manual.aspx?S=Main&P=56
M-REL? A relay you are looking at? You have an open wire between the battery and B+ in the diagnostic connector A good place to look is your EFI fuse, and the EFI relay. Assuming your ground is hooked up to the battery.
Yes. Depending on where you live, wiring could be more common than component failure. Especially in the rust belt.
What is your symptom?
No spark?
It took a long series of diagnostics to find the ECU is not being powered? I'd say the distributor is the least of your problems.
You're not going to have +B until M-Rel closes. That's not going to happen until IGSW is input to the ECU. Course, BATT needs to be hot before any of this can happen. And answer CRE's question...
You're not going to have +B until M-Rel closes. That's not going to happen until IGSW is input to the ECU. Course, BATT needs to be hot before any of this can happen. And answer CRE's question...
All of the electrical systems have power, windows, locks, lumbar support, tems, the only thing that doesn't work or register is the fuel gauge. The EFI fuse and relay tested good.
There is no spark and no electricity at the four wire connector going into the distributor. Most of the wires at the ECU show that they have between 11 and 12 volts going through them from the battery (as per the tests in the TSRM with the ignition in the ON position).
There is also electricity going into and out of the igniter and coil.
I was wondering if it could be a bad ground wire?
The car cranks all day, but doesn't generate spark. My friend whose shop the car is at used to be the head mechanic at a local Toyota dealership and he tested the distributer for me and said it was good. I was also considering bypassing the existing wires from the ecu to the distributer by cutting them and splicing in new wires, do you guys think that that would be a reasonable approach?
There is no spark and no electricity at the four wire connector going into the distributor. Most of the wires at the ECU show that they have between 11 and 12 volts going through them from the battery (as per the tests in the TSRM with the ignition in the ON position).
There is also electricity going into and out of the igniter and coil.
I was wondering if it could be a bad ground wire?
The car cranks all day, but doesn't generate spark. My friend whose shop the car is at used to be the head mechanic at a local Toyota dealership and he tested the distributer for me and said it was good. I was also considering bypassing the existing wires from the ecu to the distributer by cutting them and splicing in new wires, do you guys think that that would be a reasonable approach?
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jetjock;1034180 said:
Not sure off the top of my head what the CEL is, (I'm at work right now) what I meant by no power at M-REL was that at that wire coming out of the ECU with the key in the ON position there was no measurable current. I'm going to check the continuity of the relay itself either tonight or tomorrow morning.
kwutzo;1034587 said:
The same as the MIL.
So he said the distributor worked okay, what else did he say?
The distributor has to be spinning to generate a signal. Did you look at the EWD?
I pulled up that diagram since I think you didn't. The ECU supplies ground to that relay, not power. That is typical for it to be that way.
But lets go back to no power at B+ in the check connector. JJ pointed out that the EFI relay has to close for that. The relay has a control side and an operational side. That is the small pins and large pins. Does your EFI fuse have power on both sides of it?
I'm going to recheck everything tomorrow morning and get an exact report on how he tested the distributer. Thanks again to everybody for your help and giving me this crash-course in 7mge electrical. Hopefully I'll be able to get it running soon.....
BTW I feel retarded now for not realizing what you meant by CEL. The super monitor alternates between no codes and only code 52. Usually says Engine OK
BTW I feel retarded now for not realizing what you meant by CEL. The super monitor alternates between no codes and only code 52. Usually says Engine OK
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OK, some updates.
I now have power to the ECU and all electrical systems are go. Thanks everybody for your advice. CEL comes on with the key, but SuperMonitor says Engine OK.
Problem....Still no spark from the distributor! I have spark coming from the high tension cord to the distributor, but no spark from the distributor to the plugs.
The green connector is connected securely, the 4 wires test good from the distributor to the ECU with an ohm meter, there is no current at any of the wires with the key in the ON position.
The resistance coils in the distributor test good.
Is there supposed to be power at this connector from the ON position? My mechanic says that he believes there is supposed to be power here in order for the distributer to know which cylinder to fire? Is that really how it works? If so, how do I get power to it? If not, what else might be my problem here?:1zhelp: :3d_frown:
I now have power to the ECU and all electrical systems are go. Thanks everybody for your advice. CEL comes on with the key, but SuperMonitor says Engine OK.
Problem....Still no spark from the distributor! I have spark coming from the high tension cord to the distributor, but no spark from the distributor to the plugs.
The green connector is connected securely, the 4 wires test good from the distributor to the ECU with an ohm meter, there is no current at any of the wires with the key in the ON position.
The resistance coils in the distributor test good.
Is there supposed to be power at this connector from the ON position? My mechanic says that he believes there is supposed to be power here in order for the distributer to know which cylinder to fire? Is that really how it works? If so, how do I get power to it? If not, what else might be my problem here?:1zhelp: :3d_frown: