No power to injectors

[Highway420racer]

Whats up guys I have a '91 talon awd auto and its not getting power to all 4 injectors i replaced the ECU, every sensor i could think of even the efi relay and still get nothing. I've used a test light and get no sign of life from the wires but it gets spark. I'm starting think that part of the wiring harness might of dead but I'm not sure ??? any ideas ???

 

[steve]

If you look at the wiring diagram you'll see that the injector circuit is very simple.
Power comes from the battery through the MPI fuse to the injector resistor pack on the firewall where it runs to each of the 4 resistors and from there to pin 1 of each injector.

Each Pin 2 on an injectors runs to a unique pin on the ECU where it's grounded when the ECU want to fire the injector.

So with your voltmeter black probe grounded you should find 12v at the battery and both sides of the MPI fuse on the positive terminal. You should also see it all the time on pin 10 of the MPI relay in the center console and on pins 4 and 5 when the ignition switch is on.
While the ignition is on you should see 12v on the red wire running to pin 3 of the injector resistor connector and on the other 4 wires in that harness while it's connected. Lastly you should see 12v at the injector connector on various black with some color striped wires running to pin 1. With the injectors plugged in you should also see battery voltage at the ECU pins for the injectors since it the ECU isn't causing any current to flow ther isn't any voltage drop. The fact that you see battery voltage at the ECU in between firing the injectors is one what the ECU can tell if the injector or wiring is broken and throw a code.

So take a look and figure out where the process breaks to find your problem.

Steve

 

[1gcrazy]

If you look at the wiring diagram you'll see that the injector circuit is very simple.
Power comes from the battery through the MPI fuse to the injector resistor pack on the firewall where it runs to each of the 4 resistors and from there to pin 1 of each injector.

Each Pin 2 on an injectors runs to a unique pin on the ECU where it's grounded when the ECU want to fire the injector.

So with your voltmeter black probe grounded you should find 12v at the battery and both sides of the MPI fuse on the positive terminal. You should also see it all the time on pin 10 of the MPI relay in the center console and on pins 4 and 5 when the ignition switch is on.
While the ignition is on you should see 12v on the red wire running to pin 3 of the injector resistor connector and on the other 4 wires in that harness while it's connected. Lastly you should see 12v at the injector connector on various black with some color striped wires running to pin 1. With the injectors plugged in you should also see battery voltage at the ECU pins for the injectors since it the ECU isn't causing any current to flow ther isn't any voltage drop. The fact that you see battery voltage at the ECU in between firing the injectors is one what the ECU can tell if the injector or wiring is broken and throw a code.

So take a look and figure out where the process breaks to find your problem.

Steve

Wow...I feel privileged to share your first name...Nice job, I bet you did that all by memory too huh.
Us Steves are just slick like that

 

[steve]

I cheated and looked up the wire colors and pin numbers for accuracy

 

[steve]

I took a test light and I'm getting power to the injectors but some how they are not triggering. I'm not sure if its a ground or something but I replaced the ecu and the efi box next to it. It has fuel in the fuel rail and I replaced the injectors twice.

I'm not sure what pins are for the injectors on the ecu so I don't know how to test it or how to go about it.

Do you have any ideas?

ECU pinout in in the VFAQ site http://www.vfaq.com/mods/ecu-harness-1G.html
91-94 wiring diagram from the people at Manual CD http://www.ecanfix.com/users/manualcd/gift/dsm/1g_circuit_diagram.pdf

Since your really suffering from a no start condition make sure you've read through Clair's tech article. I can't find the link ATM.

Steve

 

[bling5tatus]

Hey Steve, can you find that Clair's tech article you spoke of? I would like to look, I will also check google.

 

[steve]

Clare is femmeDSM. The article in question is http://www.dsmtuners.com/forums/showthread.php?p=1825130

 

[redeclipse7782]

Do 1g's have that electrical box that bolts to the middle of the firewall and looks sort of like a rectangle tent, with 4 semi-thick wires going into it? I know 2g's have this, this is what controls your injectors, make sure its plugged in and if it is try replacing it with a new one and see if it resolves your issue.

 

[steve]

The injector resistor pack doesn't control the injectors. It limits the current so that the low impedance injectors don't burn out the drivers in the ECU which does control the injectors.

Steve

 

[big_country]

I just want say thanks for the knoledge bestowed upon me in this post which should allow me to solve my no start problem. after 1000 dollars at two shops it is time to take matters in my own hands and actually fix something!!

 

[ShawnsGarage]

If you want something done right do it yourself that way you have noone else to blame.