12.7 questions

Discussion in 'Heavy Duty Diesel Truck Mechanics Forum' started by Wanabe1, Jun 17, 2019.

  1. Rideandrepair

    Rideandrepair Road Train Member

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    @Shaggy76 might chime in on fuel shutoff selinoid. He referenced one on this forum a few yrs back.
     
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  3. Rideandrepair

    Rideandrepair Road Train Member

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    Well we know you’ve got fuel, Lol Sorry it didn’t work.
     
  4. Wanabe1

    Wanabe1 Light Load Member

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    Lol. And here I just thought I was cussing in the wrong language. Lol.
     
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  5. AModelCat

    AModelCat Road Train Member

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    As far as I can remember there is no need for a fuel shutoff because its all done at the injector. They're mechanically actuated electronically controlled unit injectors. A PWM signal from the ECM controls the spill port in the injector. No PWM signal, fuel doesn't get injected. It just continues on through the fuel passage in the head and out the return.
     
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  6. Rideandrepair

    Rideandrepair Road Train Member

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    I read once about a cracked ecm fuse, still lit up dash lights, but was actually bad. I’m out of guesses. Now I’m really curious what the problem is.
     
  7. Wanabe1

    Wanabe1 Light Load Member

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    Ok Swan. We are all pretty
    Oh. Yeah. This is sounding very logical just reading up all the posts will.have some lunch and button up fuel system.
     
  8. Rideandrepair

    Rideandrepair Road Train Member

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    What’s causing his RPM gauge to not work? Detroit couldn’t figure it out. Maybe a clue/ related?
     
  9. AModelCat

    AModelCat Road Train Member

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    I'm no Detroit guy by any means but if the ECM can't determine engine position, it won't inject fuel. So if the tachometer isn't reading I would immediately go check the speed sensor(s) and related wiring.
     
  10. Wanabe1

    Wanabe1 Light Load Member

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    Rpm guage? Me and detroit? Guage not working. Wanting to work truck. Took to Detroit as dealers are supposed to have computers that can just about pinpoint your problem. Also I wanted a professional to look at the truck before it went to work as my position is not one you really want to be in right now. They hook up their computer give truck clean bill of health and oh, we have signal all the way to the guage. So there is the second guage. And no refunds. After the third guage I am in there trying to show the supervisor that the wire to rpm guage is an independent wire and is he checking at the computer? Response is kinda like just shut up. We know what we are doing. Pretty common around here. And if you ain't paying any more shop time you can't have your truck on our property. I was like wow! That was educational and I will hurry right back first sign of my next problem. Lol so I take across town to this guy. He has a few wrecks over there and he is trying to learn too cuz they do the same to him. The voltage that is supposed to govern rpm guage is way high like 12.6 volts and when the truck does run voltage doesn't change more than a couple of tenths if a volt. And it is the same all the way to ecm. I finally did find the wire as it was in the wrong place in the plug. Finally I was looking at a spare harness and found the wire. We did a lot switched ecm momentarily but got lots of codes then. Must have been for different style ddec3. But finally it seemed to run fine and I didn't need guage to shift leased truck. Drove to my house to grease etc. Now this problem. Seems pretty sure we got fuel. The earlier fella made a lot of sense. There is a signal comes from your ecm to function injector otherwise she passes right on by. Will post some more in a bit, but I'm starving. Lol.
     
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  11. Wanabe1

    Wanabe1 Light Load Member

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    Oh. Speed sensors? Now, speedometer does work. This and engine sound is why I can shift without rpm guage. Are these the wires sticking out the rear of transmission?
     
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