no voltage at injectors

Posted by compression, Mar 18, 2011
Electrical Tech - Wiring, turbo timers, electronic boost controllers, gauges, fuses, wiring harnesses, wire tucks, car audio, and all other electrical component discussions.

  1. compression

    compression Proven Member

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    im supposed to get 12v from one of the pins in the injector plug im getting nothing.

    car wont start obviously, i am getting spark, injectors arent pulsing or anything, i have ecm link with speed density and im not sure if its set up correctly, but even with the wrong/no mafs the injectors should still pulse, or at least have voltage. i have been sick lately and my head isnt very clear so if im being to vague just let me know.

    ive checked the fuses, in car, underhood , and on the battery they were all ok as far as i remember,

    the resistor pack is plugged in to a connector with a yellow & black wire.

    the cam angle sensor is on and plugged in may or may not be 180* out ive swapped it both way just for curiousity.

    ecu is getting power (check engine light comes on then goes off after 5 seconds)

    im confused, sick and tired . any help would be EXTREMELY appreciated.
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  2. sniver

    sniver Proven Member

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    Ok so we need to figure out why the injectors are not getting power.

    If the ecu light comes on, I think its safe to say the the mpi is powering up. that basically leaves you a wiring problem. Ensure you have power at pin 102 on the ecu( with key on), and if you do test the voltage on plug that goes to the resistor. pin 3, its red just like pin 102 for the ecu.

    The injectors do not get a full 12volts FYI, they get something like 1.5-3. not positive on the exact though.


    If memory serves me correctly.. for the CAS proper setting, you set the timing belt like your going to change the belt, you know properly aligned at top dead center. Then you'll see the cas flag has a dot on one side, this faces up, install the cas, Then set timing as required.
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  3. steve

    steve DSM Wiseman

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    The injector resistor plugs into the connector with the black/yellow, red, black/blue, black/white, and black/red wires. The connector with the blue, red, yellow, white, red, and black wires is for the ISC.

    You may have them swapped, it's seems to be a common problem.

    It's battery voltage you'll see at the injector when there is no load. When the injector is firing the resistor and injector make up a voltage divider between the battery and ground.

    The injectors are powered from the MPI relay so you need to make sure the ECU is powering up and turning the MPI relay on.
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  4. compression

    compression Proven Member

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    cars at my fathers shop , going there tomorrow to try and get it get fired up. just need a little help for things to check for, last time my super huge major problem was , i didnt have something plugged in , im praying this is the same situation.

    come to think of it, the resistor is plugged into a connector that has a YELLOW wire, not a black/yellow (oh god please be so)

    i never really knew about the correct way of setting the cas, i usually just put it on if it doesnt run flip it. good to know!

    so for some reason if it ISNT the plug issue, i have to ensurepower at pin 102 on ecu. injectors get their power from the mpi , so if the mpi is getting power, which my ecu seems to be working fine because dsmlink connects and everything. is there any specific fuse that would cause an issue?
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  5. steve

    steve DSM Wiseman

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    If you can talk to the ECU with DSMLink the MPI relay is turning on.

    The red wire running to pin 3 of the injector resistor is the MPI power, just check it at that connector. If it's not there with the key turned on you'll have to trace it back ti the relay. No fuses between the two. The only MPI fuse is the one at the battery.
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  6. compression

    compression Proven Member

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    what would be the reason turning the key doesnt turn the starter? the tuning the key on will activate at least one of the fuses in the kick panel, i have my gauges wired to it. and could this issue somehow be related? im just trying to get all my ducks in a row, once i get there im pretty much internetless and on my own LOL.
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  7. sniver

    sniver Proven Member

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    I think Idescribed how to check the ignition switch. Maybe not?

    The mpi power is not what feeds the ignition switch.

    Did I link a copy of the fsm last time we talked?

    Either you have a bad switch,starter relay, or wire going to the starter. You have power to the switch, it turns the ecu on. And you make it work with a seperate button, so the starters good.



    Sent from my Droid
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  8. steve

    steve DSM Wiseman

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    The ECU doesn't turn on if you don't have power to the ignition switch since it gets a signal from the RUN position as input to activate the MPI relay.

    The starter signal comes from the ignition switch and runs through the theft alarm relay if present, then through the starter relay before going to the starter solenoid. If the clutch safety switch isn't depressed or bad the starter relay will block the signal from reaching the starter solenoid.

    If you don't have a copy of the FSM it going to be hard for you to fix whatever is wrong.
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  9. compression

    compression Proven Member

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    I'm not sure the frustration is getting the better of me. I fixed the injector issue. Was the plug. Now new issue. Car has fuel and spark but won't start. I'm getting a throttle position circuit malfunction code. I have a 90 but a 91 tps for the s90 throttlebody I'm running. Hooked all the wires up except the one all green wire think it's the ips . Could that cause it not to start?

    well i finally got everything back together and ready to run! wouldnt start. compression test came out as follows 1-4 , 0-90-30-30
    cylinder one has bent valve i think , with the cams out the valves should be completely sealed, it blows right through the exhaust and out the turbo. and with the cams out the other cylinders sealed perfect fine. so im not sure if theres a problem with the cams or the valves, they are 1mm os titanium and i have comp 101200 cams. i havent removed the head yet so i have no idea whats accually wrong, but thanks for all the help you guys helped me solve the original issue!
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  10. sniver

    sniver Proven Member

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    Well I can assure you of one thing, its definately a DSM.
    Sorry to hear you have additional issue, but it sounds certain the head has to come off. Either a valve is bent, or it has debris caught in a valve.



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  11. compression

    compression Proven Member

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    Dsm or not , everything thus far has been my fault :coy:
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