New To Stangnet And Need Help

Discussion in '1994 - 1995 Specific Tech' started by vj318, Jun 2, 2014.

  1. vj318

    vj318 New Member

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    hello I,m new to stangnet and have already enjoyed reading some of the posts. my son and I are working on a 94 mustang v-6 with a 5-spd trans that he got cheap because it supposedly had a dead cylinder on the drivers side rear. a good motor came with the deal. before removing the motor and installing the other motor ,I decided to checkout the dead cylinder myself and found 150lbs compression. after pulling the intake off we cranked the engine over and could see that no fuel was comeing out of the injector. the injector next to it was squirting fuel like it should so I moved the wire connector to the injector that wasn't working and now it works good , so I know the injector is not the problem. with the key on the voltage on each connector is 12v. everything seems to be ok but that connector will not make any injector work. I pulled the large square connector apart that is next to the bulkhead on the passenger side. I found the correct pins that went to that peticular injector and put 12v to those pins and got the injector to squirt fuel, so I know the connector and wires are ok. that is about as far as my knowledge will take me and I really need some help. I,m hopeing someone can help me determine why just this one injector is not getting triggerd when I know the injector is good and there is 12v to it. I,m hopeing someone out there may have had this same problem and knows the fix for it. thanks in advance. will post some pics of the car as soon as I can figure out how.
     
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  2. Noobz347

    Noobz347 Stangnet Facilities Maint Tech... Er... Janitor
    Admin Dude

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    What you need:

    Multimeter
    Soldering Iron
    Solder
    Exacto Knife
    Shrink tube
    Cigarette Lighter

    Go back to the connector that was intermittent and identify the exact location of the problem with the intermittent connection.

    Surgically removed the insulation for the problem area. Solder and re-insulate the faulty connection using the shrink tube.

    Replace any other areas that look broken or brittle.

    If you do not possess the skills necessary to do these things then find a buddy who does and observe carefully.

    In place of a multimeter, you can also use a noid light.

    NOTE:
    I recommend that you never reinstall an engine bay connector without the use of a silicon based connector grease spread liberally into each connector that you reinstall/reattach.
    (this can cure a lot of weird (read: ghost) problems that can occur when the engine bay sees moisture)


    What's great is that you already have this specific problem localized so you shouldn't have much trouble fixing it.

    DO NOT do some hack job repair and expect it to last. Do electrical repairs BETTER than what came from the factory and never have to touch that piece again. Harnesses will drive you to the damned insane asylum if they are not repaired correctly.

    The soldering iron should be a decent one. Skip the hardware store and go to Radio Shack or hit up an electronics store. For most automotive applications, a pen type 60+ watt iron will do the job nicely. Skip the soldering gun unless you're trying to solder very large gauge wire.

    Watch a Youtube video about 1) seasoning and preparing the soldering iron tip and 2) how to solder effectively.
     
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  3. revhead347

    revhead347 I have face herpes.

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    Looks like you are using solid diagnostic technique, and have already isolated the problem very well. It will likely be a cheap repair if you follow the instructions as before. You can buy those injector pigtails at Advance and Autozone. Replacing that would help. Also check the main connection to the computer which is under the kick panel on the passenger side of the car. Use electrical contact cleaner to ensure good connections there. I think you will have this worked out quickly.

    Kurt
     
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  4. vj318

    vj318 New Member

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    Kurt[/QUOTE]
     
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  5. WhiteCobra95

    WhiteCobra95 Member

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    I think the guys have given some excellent advice.

    If I'm understanding your post correctly, Kurt is right; you're really close to figuring this one out.

    Most PFI injectors use low side drivers, where they have a constant 12 V on one side of the injector and the ECU switches the other side to ground to make them fire. You've already determined that that each connector has 12V (usually this comes from one 12V splice for all cylinders or a bank specific 12V splice if they're fused separately). You've also checked the harness back to the bulkhead connector, so the ground leg for the non-firing injector seems to be good, which means that the harness is probably good back to that point. The next step is to check the harness back to the ECU connector and verify that the ground leg for that injector is good at the ECU (by resistance check with an ohm meter between the injector pin and ECU harness pin). If that connection rings out as an open, then there's a problem between the bulkhead connection and the ECU connector. If it has continuity (low resistance, should be very close to 0 ohms), then the ECU injector driver might be toast. The driver stage going bad is far less common, but it does happen. There are also some inline testers that can be used for this check, but you're already 90% of the way there.

    Good luck!
     
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  6. vj318

    vj318 New Member

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    I guess I didn't explane the problem well enough, so I will try again. first of all there is no intermittent problem. I have 1 injector that is not being triggerd at all, either while cranking or when the engine is running. the injector is good. the connector and wires that go to the large square connector that is attached to the firewall on the passenger side are also good. when I separate this multi pinned connector and apply voltage to the 2 pins that go to the injector it spits fuel like it should. so I know that everything from the multi pin connector on the firewall to the injector is good. there is also good battery voltage getting to the injector with the ignition on. so basically the wires the connectors the voltage and the injector is good,but this one injector is just not getting triggerd. this is about as far as my knowledge will take me.
     
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  7. vj318

    vj318 New Member

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    thanks whitecobra95 your post came up on my computer after I tried to explane again the problem. thanks, as soon as I can get to it I will look for the ecu.
     
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  8. vj318

    vj318 New Member

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    ok I checked continuity from the ecu connector all of the way to the injector and it is good. I pulled the ecu out and opened it up and didn't see anything that might be burnt, but I did find a sticker on the outside of the ecu that said reprogrammed powertrain control module, and then the following modifications have been made. cal # f4zf-cd 5916. I have no idea what those #s mean. Is it safe now to assume the ecu is bad or do I need to check something else.
     
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  9. WhiteCobra95

    WhiteCobra95 Member

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    I hate to tell you to go and buy a new ECU in case that doesn't fix it, but it sure seems like you've check everything else and it's working fine. Do you have any salvage yards near by where you might be able to pick one up for a reasonable price? I've used www.car-part.com in the past to find local bone yards.

    The reprogramming sticker on the ECU surprises me. The ECUs used in the V8 cars were not re-flashable, so you can't change the calibration or software without physically changing the chip (EPROM). Maybe they did something different with the V6 controllers.
     
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  10. toyman

    SN Certified Technician

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    To clarify. Is this a V6 (3.8l) vehicle? If so the ECU is OBDII and can be flashed. This forum historically was the SN95 GT/Cobra and many may assume that issues are related to only these vehicles.
     
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  11. revhead347

    revhead347 I have face herpes.

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    The correct way to check the ECU is to send it in and have it test benched. Unfortunately that just isn't cost effective. I generally hate the idea of throwing parts at a car, but a new refurbed ECU is under $150, that might be your best option.

    Kurt
     
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  12. vj318

    vj318 New Member

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    fortunately I am in pretty good with our local wrecking yard and I am sure he will let me borrow a control module to use as a test before buying it.
     
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