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throttle position switch / trans vac reg valve

Discussion in '1982-Present GM Diesel' started by DieselBurb, Nov 8, 2002.

  1. DieselBurb

    DieselBurb 1/2 ton status

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    Why does a mechanically injected diesel need a throttle position switch /forums/images/graemlins/1zhelp.gif? Mine is unattached to the injector pump and I need to know where it goes. Also, how is the transmission vacuum regulating valve hooked up to the vacuum lines? There are not any vacuum lines hooked up to it...what does it do /forums/images/graemlins/1zhelp.gif?

    /forums/images/graemlins/burb.gif
     
  2. arveetek

    arveetek 1/2 ton status

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    The TPS is needed for the transmission.

    On a 700 equipped truck, the TPS is used to control TC lockup functions.

    On a 400 equipeed truck, the VRV (a form of a TPS) is used to control shift points.

    Which do you have? You should have either a TPS or a VRV, not both. The TPS is held to the side of the injection pump with two screws, and it has a few wires coming out of it with possibly two electrical connectors. I'm not totally sure what a VRV looks like, but it will have vacuum ports instead of wires.

    Casey
     
  3. AzzKicker

    AzzKicker 1/2 ton status

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    good post.


    How do you know if its working though. I believe its a orange wire correct? Runs from the gas peddal to somwhere in the tranny. The reason I ask is because when I bought the truck I noticed something connected to the drivers side of my 400, but until recently I found out what it was. I wanna make sure its working, how do i know. Because when I connected the closest wire(which was orange) to the switch on tranny I really didnt notice any change. So I followed the wire up to the firewall and into gas peddle, and there it seemed connected right. Is it suppos to go from peddel to the switch on the engine with 2 screws.
     
  4. DieselBurb

    DieselBurb 1/2 ton status

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    Right now, I have both, because I am finding out that sometime in the /forums/images/graemlins/burb.gif's life, the 700R4 came out and a TH400 was put in instead. The vacuum vale is on the injector pump right now and the electric TPS is just loose (well its zip-tied). How are the vacuum lines supposed to be routed? The vac modulator on the tranny is hooked up directly to the vac pump.
     
  5. arveetek

    arveetek 1/2 ton status

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    Here's what I do know:

    The VRV should be between the pump and the tranny. So basically, the lines should go from the vacuum pump, to the VRV, to the tranny. You can throw away the TPS, it's not needed for your rig.

    Passing gear (kickdown) is controlled by the switch on the accelerator inside the cab. If you don't have one, you'll need to get one in order for this function to work properly.

    Casey
     
  6. azblazor

    azblazor 1/2 ton status Premium Member

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    Mike,
    Don't throw the TPS away!! Send it to me I'll pay shipping - I need it.
    Thanks
    Mark
     
  7. BARRAZA

    BARRAZA 1/2 ton status

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    The TPS is also for control of the EGR valve on LH6/"C" code engines. It is not used at the same time as the vacuum regulator valve because Turbo 400's only came with "J" code engines, which in turn didn't have EGR. If the vacuum modulator line is hooked straight to the vacuum pump, the trans will think that the engine is always under light or no load and cause minimum speed, soft shifts. The vacuum regulator valve / transmission modulator inputs to the tranny are completely separate from the electrical downshift connection on the drivers side of a turbo 400. The electrical connection provides 12v to the solenoid when the throttle is nearly wide open for downshifts.
     
  8. DieselBurb

    DieselBurb 1/2 ton status

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    Hey, Mark. I got the old TPS off, but before I got it off, I noticed that one of the terminals had been broken off. It might could be soldered back on, but I can't guarantee that it works, especially since I don't have the trans to check it with. Let me know.

    Mike
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  9. DieselBurb

    DieselBurb 1/2 ton status

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    Thanks for the info /forums/images/graemlins/grin.gif. I got it hooked up like it was supposed to be and it made a world of difference. Thanks.

    Mike
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