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2G No power to ecu

talonater619

Probationary Member
11
1
Mar 22, 2021
riverside, California
The car is a 95 talon with a 99 engine swap.
Car cranks but won't run I have tried 3 different ecu, one 95, 97, and a 97 with ecmlink v3 and none work. I'm pretty much stuck at this point and seeing if I can get any help.

My ecu light does not turn on then off when I turn the ignition switch and am not getting fuel or spark.

Pin 80 on ecu has 12v with switch on or off
Pin 82 on ecu has 12v with switch on or off
Pin 12 has 0v with switch on or off
Pin 25 has 0v with switch on or off
Pin 38 has 0v with switch on or off
Pin 71 has 0v with switch on or off

With my mpi unplugged the black and white wire has 11.7v
with the mpi unplugged the all red wire has 0.1v

With the mpi plugged in the all red wire has 11.7v
With the mpi plugged in the black and red wire has 11.7v
With the mpi plugged in the blue green wire has 0v with the switch on or off
With the mpi plugged in the two red and black wires have 0v with the switch on or off.
Grounding Pin 5 on my mpi activates the fuel pump

I have also ran a 12v wire to pin 12 and 25 on the ecu with no luck.

Only my headlights and emergency and interior lights and door locks work, windows don't work and tach doesn't move as car cranks
 
Last edited by a moderator:

dustyboner

DSM Wiseman
1,365
620
Mar 13, 2016
abq, New_Mexico
With the mpi plugged in the two red and black wires have 0v with the switch on or off.

check fusible link #4
upload_2021-3-23_20-52-16.png



This pic is borrowed from THIS THREAD
100_4748-jpg.286794
 

dustyboner

DSM Wiseman
1,365
620
Mar 13, 2016
abq, New_Mexico
if your fusible link #4 is good, you have a problem in the wiring between FL #4 and the MPI relay
 

randman2011

Proven Member
379
164
Feb 26, 2012
Indianapolis, Indiana
Summary that you're probably familiar with but I'm just thinking out loud since I just had to set up a Megasquirt to handle this exact process.

Pin 71 is active high signal for key on ACC or ON and should only be GND with the car off. I don't actually know how or if the ECU uses this signal, though.
Pin 82 is active high signal for key in ON, so it should be GND with the car off or in ACC.
When 82 goes high and is detected by the ECU, the ECU sets pin 38 to GND.
Pulling pin 38 to GND triggers MFI relay providing power to pins 12 and 25 as well as the fuel pump relay.

A lot of your observations don't make sense and indicate two separate problems with the ignition switch, a problem with the pin 38 pull up circuit or a short at the ECU, and an open circuit between pin 38 at the ECU and the MFI relay.

With the ECU unplugged, can you recheck the behavior of pins 71, 82, and 38? Then with the ECU still unplugged, if you short pin 38 to ground, does the MFI relay activate? That could at least rule out a fair number of things.
 
Last edited:

dustyboner

DSM Wiseman
1,365
620
Mar 13, 2016
abq, New_Mexico
If i remember correctly, one of the red/black wires provides B+ to the activation coil. Since the is no voltage on the red/black wires, grounding pin 38 will do nothing.
 

talonater619

Probationary Member
11
1
Mar 22, 2021
riverside, California
Summary that you're probably familiar with but I'm just thinking out loud since I just had to set up a Megasquirt to handle this exact process.

Pin 71 is active high signal for key on ACC or ON and should only be GND with the car off. I don't actually know how or if the ECU uses this signal, though.
Pin 82 is active high signal for key in ON, so it should be GND with the car off or in ACC.
When 82 goes high and is detected by the ECU, the ECU sets pin 38 to GND.
Pulling pin 38 to GND triggers MFI relay providing power to pins 12 and 25 as well as the fuel pump relay.

A lot of your observations don't make sense and indicate two separate problems with the ignition switch, a problem with the pin 38 pull up circuit or a short at the ECU, and an open circuit between pin 38 at the ECU and the MFI relay.

With the ECU unplugged, can you recheck the behavior of pins 71, 82, and 38? Then with the ECU still unplugged, if you short pin 38 to ground, does the MFI relay activate? That could at least rule out a fair number of things.

Pin 71 and 82 is ground, pin 38 is nothing I gave it a ground from my power probe and didn't hear the mpi relay click

check fusible link #4
View attachment 625393


This pic is borrowed from THIS THREAD
100_4748-jpg.286794


I put a new fuse in and still nothing

I just noticed on my 95 fuse box the 100amp alternator fuse is by itself, but on a spare fuse box from a 99 there is big fuses there 1 60amp fuse +B and next to it is the 100amp alternator fuse. The alternator fuse is in diffrent spots and the 99 has a extra. I have attached a photo showing my current 95 fuse box in the car on top and the spare 99 below it not attached I cut it out of a 99 car a while back.
 

Attachments

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Last edited by a moderator:

talonater619

Probationary Member
11
1
Mar 22, 2021
riverside, California
Alright I got the dash lights to work and I added a 12v wire to pin 12 and the check engine light shows up but vehicle still won't start its not getting fuel
 

talonater619

Probationary Member
11
1
Mar 22, 2021
riverside, California

Steve I'm not getting power to the red wires with black stripes pin 4 or 8, so I'm assuming the wire is broken somewhere from the mpi relay to the fuse box I'm going to run a new wire from the fuse box directly to the pins 4 and 8 and see if it gets power, thanks for the diagram and post

I added a new wire from fuse box to the those and it worked. Check engine light turns on n off as it should and fuel pump is getting power. Both pin 4 and 8 on relay now have power at all times so it must of been a damaged wire somewhere in between. Vehicle still won't start so now gotta figure out why it's getting no spark
 

talonater619

Probationary Member
11
1
Mar 22, 2021
riverside, California
Just a little update changed out the spark plugs and car fired right up. The only problem now is that after I start the car it will run fine but if I shut it off and try to start it again it will run for a few seconds then shut off. If I try to start it again it will start everytime but will shut off after a few seconds. If I disconnect my battery then connect it it will start up and run again no problem. Or if I remove the ecu then plug it back in it will run no problem but as soon as I turn it off it and try to start it again it dies within a few seconds.
 

talonater619

Probationary Member
11
1
Mar 22, 2021
riverside, California
I don't know where to start. The fact that it works when you reset the ECU is puzzling. Do you have anyway to log the ECU to see what it sees?

The fact you have one harness issue makes me suspect about others.

How is your Engine Coolant Sensor wiring?
Does the mpi relay give power to pin 12 on the ecu? I'm suspecting that may be the issue. If I can't solve this issue soon I'm going to just install a new fusebox harness,engine harness and mpi relay from a donar car when I find one
 

steve

DSM Wiseman
13,713
815
Feb 3, 2002
Boulder, Colorado
Does the mpi relay give power to pin 12 on the ecu? I'm suspecting that may be the issue.

I'm forced to assume you didn't look at the prior link very closely so this may be my last response.
95mpi.gif


As you can see the battery voltage is provided to both ECU pins 25 and 12 from the output on pin 3 of the MPI relay. You should also check that the circuits that A and B feed receive battery voltage when the MPI relay activates. Get the FSM for your car to reference the rest of the wiring diagram for those circuits.
 

miguelmcv

Supporting Member
2,716
240
May 3, 2009
Fresno, California
Looks like the harness is all messed up, the problem gets worst which you are not looking for the problem (bad wire) but instead you are adding another line to source the current.

Doing it that way and not getting results makes me think the bad wire is shorting some how and making the system crazy.

Your best bet is to open the harness and fallow the wires that are bad and fix it, don’t just forget the wire and add another one, but take a look at the line and see what is wrong,

I know is a lot of work but in the long run it will be better, it will be more reliable.
The signal from the ecu to the mph relay (fuel pump) is present only when the engine is cranking, you won’t see it que switch is ON or OFF.

If you add pics or the wiring, we might catch something that you are not seeing.
 

Mironex-DSM

Probationary Member
10
0
Apr 13, 2021
Stuttgart, Europe
Hey guys i have (nearly) the same Problem On 96 eclipse.
I also dont have any voltage on pin 12 and 25.
My mpi and fuel relay doesnt trigger although there is b+ on pin 3 and pin.
I dont know if its related or not but my room Illumination (Dash light, heather panel light and keyring light) doesnt lightning.
If my key is in On Position, ill have System voltage(12 V) between
Pin 80 and ground
Pin 82 and ground
and Pin 38 and ground
My car cranks but it doesnt fire up
Im losing all my hope...
 

steve

DSM Wiseman
13,713
815
Feb 3, 2002
Boulder, Colorado
Hey guys i have (nearly) the same problem on 96 eclipse.
I also dont have any voltage on pin 12 and 25.

If my key is in On Position, ill have System voltage(12 V) between

Pin 38 and ground

The ECU should be pulling pin 38 to ground to activate the MPI relay which should then provide 12v to pins 12 and 13.

When did this start happening and what happens if you ground pin 38?
 

Mironex-DSM

Probationary Member
10
0
Apr 13, 2021
Stuttgart, Europe
The ECU should be pulling pin 38 to ground to activate the MPI relay which should then provide 12v to pins 12 and 13.

When did this start happening and what happens if you ground pin 38?
It started once after i was parking, suddently my rpm started to drop and then my car went off.
As i tried to start it, it just Cranks. Somethimes like 1 in 100 cases its firing up, but if i turn it off and on again it wont start.

If Pin 38 has 12V and i ground it, wouldnt ist be a short circuit ?
 

steve

DSM Wiseman
13,713
815
Feb 3, 2002
Boulder, Colorado
If Pin 38 has 12V and i ground it, wouldnt ist be a short circuit ?
If you look at the wiring diagram above you'll see that power for both the ECU and the MPI relay comes from Fusible Link #4 on the Red with Black stripe wire and splits off to connect to pins 4 and 8 or the MPI relay.

MPI relay pin 8 is the coil of the relay and has a diode in series to block any reverse current. The relay coil has resistance so the combination of diode and coil limits the current that can flow from power to ground. It's not a short because of this resistance.

In normal operation when the ECU isn't trying to activate the MPI relay the voltage at ECU pin 38 floats up to battery voltage and no current is flowing but when the ECU wants to activate the MPI relay is pulls pin 38 to ground causing current to flow in the coil and the relay to close the contacts between pin 4 and pins 2 and 3, switching power to ECU pins 12 and 25 as well as powering the other things on the MPI circuit.
 

Mironex-DSM

Probationary Member
10
0
Apr 13, 2021
Stuttgart, Europe
If you look at the wiring diagram above you'll see that power for both the ECU and the MPI relay comes from Fusible Link #4 on the Red with Black stripe wire and splits off to connect to pins 4 and 8 or the MPI relay.

MPI relay pin 8 is the coil of the relay and has a diode in series to block any reverse current. The relay coil has resistance so the combination of diode and coil limits the current that can flow from power to ground. It's not a short because of this resistance.

In normal operation when the ECU isn't trying to activate the MPI relay the voltage at ECU pin 38 floats up to battery voltage and no current is flowing but when the ECU wants to activate the MPI relay is pulls pin 38 to ground causing current to flow in the coil and the relay to close the contacts between pin 4 and pins 2 and 3, switching power to ECU pins 12 and 25 as well as powering the other things on the MPI circuit.

Okey , ill try to ground pin 38 later.
I have an original MUT 2 Tester, if i test my Voltage with it, its showing me 0V. Shouldn't it show me my onboard Voltage (12V) ?
 

Mironex-DSM

Probationary Member
10
0
Apr 13, 2021
Stuttgart, Europe
If you look at the wiring diagram above you'll see that power for both the ECU and the MPI relay comes from Fusible Link #4 on the Red with Black stripe wire and splits off to connect to pins 4 and 8 or the MPI relay.

MPI relay pin 8 is the coil of the relay and has a diode in series to block any reverse current. The relay coil has resistance so the combination of diode and coil limits the current that can flow from power to ground. It's not a short because of this resistance.

In normal operation when the ECU isn't trying to activate the MPI relay the voltage at ECU pin 38 floats up to battery voltage and no current is flowing but when the ECU wants to activate the MPI relay is pulls pin 38 to ground causing current to flow in the coil and the relay to close the contacts between pin 4 and pins 2 and 3, switching power to ECU pins 12 and 25 as well as powering the other things on the MPI circuit.
So i connected Pin 38 to ground, the cel turned on, mpi and fuel relay clicked.
As i tried to start it was just cranking but didn´t fired up.
I also connected 12V to Pin 12 and Pin 25 (Power source), cel went on and same as before just cranking without firing,
sometimes its "tried" to fire up like for 1 second but went straight off
 

dustyboner

DSM Wiseman
1,365
620
Mar 13, 2016
abq, New_Mexico
could i be an issue with the immobilizer? if its keeping the fuel pump relay from activating it would explain the no start. If the CEL is on what trouble codes are you getting?
 
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