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Stealth and 3000GT General Info General Questions and Comments regarding the Stealth and 3000GT. Newbie questions welcome.

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  #1  
Old - December 11th, 2005, 04:38 AM
ARC ARC is offline
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Join Date: Dec 2005
Location: KY
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'91 Stealth TT - MFI relay / ECU ????

I have 1991 Stealth RT/TT that will crank but not start. CE light not working.

Power is not being supplied to ecu from MFI relay. I can get the car to start and run by jumping power to both sides of the relay. The CE light will come on, the car will start and run fine. (only a quick test, I don't wont to drive it this way- don't know what may fry -- does anyone know the possible consequences of jumping the relay from a switched power supply?)

I think that the relay has two power supply wires, but I am not sure. One side is 'hot', the other side seems to be dead. I replaced the relay, no change.

The ECU fuse in the driver side kick-panel is fine.

The ECI fuse under the hood is fine, and power is reaching that point.

I intend to pull the fuse panel under the ECI fuse and make sure that the wiring is sound. I've heard that this is occasionally a problem.

What is left except for the ecu itself? Is there an 'trigger' circuit that supplies power to the MFI relay?

Any other suggestions on what would stop power from being delivered to the MFI relay?

I really appreciate the help.
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  #2  
Old - December 26th, 2005, 02:17 PM
steve steve is offline
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Join Date: Feb 2004
Location: St. Charles, IL
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Quote:
Originally Posted by ARC
Is there an 'trigger' circuit that supplies power to the MFI relay?
The trigger circuit doesn't supply power, it pulls the one side of the MPI relay coil to ground when the ignition switch turns on to energise the relay and switch the voltage from pin 10 to pins 4 & 5.

You can test if this is the problem by grounding pin 8 (Blue w/Green stripe) on the MPI relay and see if the Check Engine Light comes on for five seconds (ECU booting) and car runs.

I see this happen alot on DSM's where the capacitor leakage can eat the circuit traces involved. On 3S ECUs I see it when people miswire a turbo timer and blow the transistor that pulls the relay low but capacitor damage could also cause problems.

Have you pulled and checked your ECU. the 1G ECUs are prone to capacitor leakage. I fix the DSM and 3S ECUs all the time.

Steve
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  #3  
Old - December 26th, 2005, 10:06 PM
ARC ARC is offline
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Join Date: Dec 2005
Location: KY
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Thanks for the info. I have replaced the relay and checked the ECU in another car - it started and ran in a different car (same year and model). I am thinking that it may be a wiring problem between the fuse box (under hood) and the MFI.

Could the ignition switch cause this?

Thanks,
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  #4  
Old - December 26th, 2005, 10:37 PM
steve steve is offline
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Quote:
Originally Posted by ARC
Could the ignition switch cause this?
It could but it should cause other problems too that would keep the car from running if all you did was jump pin 10 to pins 4 and 5 before.

What did you do?

Steve
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  #5  
Old - December 27th, 2005, 01:56 AM
RT-TT RT-TT is offline
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Did you ever remove your dash?

I was having the exact problems, but there was a little plug under the dash behind the passenger side vent that wasnt plugged in here is a link

http://img218.imageshack.us/img218/4...12260192nv.jpg

Its the white one on the right in the foreground.

If thats plugged in chech the connector at the fuel pump. Also check the fuel pump relay and resistor underneath the airbox.
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  #6  
Old - December 27th, 2005, 04:21 AM
ARC ARC is offline
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Quote:
It could but it should cause other problems too that would keep the car from running if all you did was jump pin 10 to pins 4 and 5 before.
This is all that I did. BTW, if I remember correctly there are only 9 actual pins on my relay. What colors are the wires going to pins 4, 5 and 10 and where do they go? I have a manual but it does not show wire colors.

I have heard from someone that the underhood fuse box sometimes fails and causes the symptoms that my car has. I am out of town for a day or so, but by the end of the week should be able to return my ecu and recheck things.

Quote:
Did you ever remove your dash?
I have never removed the dash, but I have removed the digital display unit for the AC in the center of the dash (above the stereo) and the climate control computer. In fact, the only removal that I have done is from the center area while repairing climate control and stereo.


Would it be possible that the plugs would have become accidentally disconnected by my working in the center area? The car was running fine, I removed the climate control unit (display unit) and the car hasn't started or ran since.

Thanks, any suggestions appreciated.
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  #7  
Old - December 27th, 2005, 12:14 PM
steve steve is offline
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Quote:
Originally Posted by ARC
This is all that I did. BTW, if I remember correctly there are only 9 actual pins on my relay. What colors are the wires going to pins 4, 5 and 10 and where do they go? I have a manual but it does not show wire colors.
Pin 1 N.C.
Pin 2 Black/Blue (switched power output from pin 3 to Fuel Pump)
Pin 3 Black/White (power input from 15A Ignition fuse 12 for Fuel Pump and Fuel Pump Relay coil 2)
Pin 4 Black/Red (switched power output from pin 10 to ECU pin 12 and 25)
Pin 5 Red (switched power output from pin 10 to Engine Harness)
Pin 6 Black (ground for Fuel Pump Relay coil 1)
Pin 7 White/Red (ECU pin 8 control line for Fuel Pump Relay coil 2)
Pin 8 Blue/Green (ECU pin 108 control line for MPI relay coil)
Pin 9 Black/Yellow (power from Starter Relay for Fuel Pump Relay coil 1)
Pin 10 Red/Black (power input from 20A EFI fuse 1 for MPI)

All of this is in the real Factory Service Manuals under the MPI Circuit in the fuel section or in the electrical manual. Also, on the 3S Manual CD
http://www.manualcd.com

The box called the MPI relay has two independant relays inside, one actually for the MPI circuit and one for the Fuel Pump (not to be confused with the Fuel Pump voltage relay under the hood).

Steve
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  #8  
Old - December 27th, 2005, 11:04 PM
RT-TT RT-TT is offline
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Quote:
Originally Posted by ARC
This is all that I did. BTW, if I remember correctly there are only 9 actual pins on my relay. What colors are the wires going to pins 4, 5 and 10 and where do they go? I have a manual but it does not show wire colors.

I have heard from someone that the underhood fuse box sometimes fails and causes the symptoms that my car has. I am out of town for a day or so, but by the end of the week should be able to return my ecu and recheck things.


I have never removed the dash, but I have removed the digital display unit for the AC in the center of the dash (above the stereo) and the climate control computer. In fact, the only removal that I have done is from the center area while repairing climate control and stereo.


Would it be possible that the plugs would have become accidentally disconnected by my working in the center area? The car was running fine, I removed the climate control unit (display unit) and the car hasn't started or ran since.

Thanks, any suggestions appreciated.

yeah dude mine did it after i removed my ac system. Trust me check that connector.
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  #9  
Old - February 22nd, 2011, 10:15 PM
vr4nin vr4nin is offline
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Re: '91 Stealth TT - MFI relay / ECU ????

OLD POST but hope your all still here. I have a problem identical to this. My car ran fine a 92 vr4. It was missing driving home last week I got it home. I kept it running and looked all under the hood then turned off car. tried to start it within minutes now It wont spark now and wont start at all. It has a real bad key ignition switch and it will crank but not start. I need help and Im no mechanic. Need help bad. I hope this post is not to old. Please tell me how you solved yours? I am sending my ECU in to be rebuilt/tested if needed but it never leaked and I replaced the caps 6 months ago anyway. This came out of nowhere and I need help bad. I live in Utah. dave email please, im limited to PC access and it comes to my company paid phone , email is vr4nin@msn.com NO SPARK. I have checked all I have read and no luck. HELP,. SOS this is our only car right now cause of my job loss.. Dave
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  #10  
Old - February 14th, 2017, 03:30 PM
Vr4 fast Vr4 fast is offline
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Re: '91 Stealth TT - MFI relay / ECU ????

new here ...dont understand it all , need help tho..
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  #11  
Old - February 14th, 2017, 03:33 PM
Vr4 fast Vr4 fast is offline
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Re: '91 Stealth TT - MFI relay / ECU ????

would like insight ..from u
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