Crazy Electrical issue with EFI system

cre · 04-29-2010, 02:26 AM

Okay, sorry... I looked back over what you're doing and see what you're doing... powering +B and +1B from the BATT line. IMO it would be better to bypass the relay directly than to introduce power from a line which is already running all over the place (noise) and may be suspect itself.

Oh, and the circuit opening relay which powers the fuel pump is switched by the main EFI relay AND the ECU has an emergency shutoff should it believe there is no air flow... so ECU and main EFI relay are both possibilities for no power to the fuel pump. The relay is more likely unless you've had a blown heater core steam the innards of the ECU.

Cameroonski · 04-30-2010, 01:45 AM

I switched out the ECU and the ignition switch today and still no luck. All my relays are good, they have been tested and switched and juggled and they work. My problem is this...

M-REL only has .08 volts at the computer, as well as at the EFI main relay with the ignition on. When I apply voltage to the computer side of the the resistor side of the relay, it works and the car turns on but with funky idle issues.

What i will do tomorow is do this bypass and see if im getting voltage at M-REL... i think. If i am, I know the wire is good, if not there is another problem somewhere else and im SOL.

Cre, thanks. Any other advice? I am totally confused here...

Cameroonski · 04-30-2010, 11:11 PM

Here's the update...

The Check Engine light was not coming on with the ignition on. It DOES come on when terminal W is connected to E1 (computer ground) as well as a body ground. The computer ground into the engine block is good.

I'm also getting these voltages...

BATT has 12v
M-REL still has about .08v
IG S/W had about 1.23v
+B is not getting anything

Also, on the Diagnostic Box...

From +B and the battery i have 12v, and from Fp and the batter i have 12v, but both to the same side of the battery and when i test it in between them it is 0v. Im not sure if this means anything...

All of this seems like the ECU is funky, but i have tried two different ECUs, and i find it highly unlikely that the same odd problem would lie in both. So short circuit somewhere maybe?

Please i need some help..

88'sup · 08-13-2022, 12:22 PM

What was the problem here? I have exact thesame issue! who can help me bringing my fully rebuild 88' back on the road again?

Bru · 08-16-2022, 09:22 PM

Describe your particular symptoms. Does it crank but not start? Does it not crank when it's hot unless you cycle the switch many times? If that's the case then check the EFI relay behind the battery. These can go bad from heat soak and give an intermittent failing. Here is a link to the online wire diagram on the starter circuit page. http://cygnusx1.net/Supra/Library/TS....aspx?S=D&P=32

04-29-2010, 02:26 AM	#1
cre Toyota Racing Development Join Date: Apr 2007 Posts: 5,038	Okay, sorry... I looked back over what you're doing and see what you're doing... powering +B and +1B from the BATT line. IMO it would be better to bypass the relay directly than to introduce power from a line which is already running all over the place (noise) and may be suspect itself. Oh, and the circuit opening relay which powers the fuel pump is switched by the main EFI relay AND the ECU has an emergency shutoff should it believe there is no air flow... so ECU and main EFI relay are both possibilities for no power to the fuel pump. The relay is more likely unless you've had a blown heater core steam the innards of the ECU. __________________ If something breaks or you need to contact a member of the administration please post HERE. Unless it's a private or administration matter please post it on the forum. It benefits no one else if car related questions aren't posted for future users and takes away from the time I'm able to spend helping on the rest of the forum. If you're so inclined I'm always more than happy to accept tips via PayPal. Tip Jar ---> Last edited by cre; 04-29-2010 at 02:31 AM.

08-13-2022, 12:22 PM	#4
88'sup Stock Join Date: Aug 2022 Location: Holland Posts: 1	??? What was the problem here? I have exact thesame issue! who can help me bringing my fully rebuild 88' back on the road again?

08-16-2022, 09:22 PM	#5
Bru Bone Stock w Upgrades ;-) Join Date: Apr 2010 Location: Tampa Bay Posts: 214	Describe your particular symptoms. Does it crank but not start? Does it not crank when it's hot unless you cycle the switch many times? If that's the case then check the EFI relay behind the battery. These can go bad from heat soak and give an intermittent failing. Here is a link to the online wire diagram on the starter circuit page. http://cygnusx1.net/Supra/Library/TS....aspx?S=D&P=32 Last edited by Bru; 08-17-2022 at 03:04 PM.

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04-30-2010, 01:45 AM	#2
Cameroonski 3" Exhaust Join Date: Dec 2009 Location: Austin, Tx Posts: 68	I switched out the ECU and the ignition switch today and still no luck. All my relays are good, they have been tested and switched and juggled and they work. My problem is this... M-REL only has .08 volts at the computer, as well as at the EFI main relay with the ignition on. When I apply voltage to the computer side of the the resistor side of the relay, it works and the car turns on but with funky idle issues. What i will do tomorow is do this bypass and see if im getting voltage at M-REL... i think. If i am, I know the wire is good, if not there is another problem somewhere else and im SOL. Cre, thanks. Any other advice? I am totally confused here...

04-30-2010, 11:11 PM	#3
Cameroonski 3" Exhaust Join Date: Dec 2009 Location: Austin, Tx Posts: 68	Here's the update... The Check Engine light was not coming on with the ignition on. It DOES come on when terminal W is connected to E1 (computer ground) as well as a body ground. The computer ground into the engine block is good. I'm also getting these voltages... BATT has 12v M-REL still has about .08v IG S/W had about 1.23v +B is not getting anything Also, on the Diagnostic Box... From +B and the battery i have 12v, and from Fp and the batter i have 12v, but both to the same side of the battery and when i test it in between them it is 0v. Im not sure if this means anything... All of this seems like the ECU is funky, but i have tried two different ECUs, and i find it highly unlikely that the same odd problem would lie in both. So short circuit somewhere maybe? Please i need some help..