Dakota Digital VHX (88-94 gauges)

Discussion in 'Audio + Electronics' started by D_EATON, May 22, 2016.

  1. PlayingWithTBI

    PlayingWithTBI Desert Old Guy

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    On my 88 there's 2 different oil pressure switches/senders. The fuel pump is a switch mounted vertically behind the china rail. The sender for the gauge is just below the head on the block.

    upload_2021-2-11_14-10-30.png
     
  2. Flurvin

    Flurvin Newbie

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    I have recently installed a Dakota dash in my 91 C1500. I used the supplied oil pressure sensor in the stock location of the original. This as I found out later doesn’t work since the original controls fuel pressure.

    Where do you get your oil pressure reading from? My truck doesn’t have a second oil pressure sensor location as the above diagram shows.
     
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  3. AK49BWL

    AK49BWL GMT400 Forever!

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    It's not supposed to control fuel pressure, that's the regulator's job. If you're not getting fuel, then you need to check your fuel pump relay. The oil pressure switch is only a backup for that relay.
     
  4. Flurvin

    Flurvin Newbie

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    When I installed the Dakota oil pressure sensor in the stock location, the truck didn’t run right. Seemed like it was missing only on idle and rpms were between 300-600. Then it just wouldn’t start. I started chasing down all the ignition components. Replaced distributer, coil and wires. I still couldn’t get it to run.
    I had someone crank it over so I could check timing and get in the ball park of 0 degrees with no advance from the ecu. To prevent it from flooding out I disconnected the fuel relay. It then fired right up and ran on the fuel in the throttle body. So I plugged the relay back in. Truck fires up but was back to running rough.
    I then changed the Dakota oil sensor back to the stock one and it is now running great. Back to normal.

    This leaves me with no oil pressure gauge. Just wondering how others got there gauge to work.
     
  5. PlayingWithTBI

    PlayingWithTBI Desert Old Guy

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    When I installed my DD dash I used the OE oil pressure sender on the block as per the drawing I posted above. Works great. The switch (not a sensor) you were messing with bypasses the fuel pump relay and turns on the pump. Note: the only sender we replaced was the temp sender in the head between #s 1 & 3.
    I've had it this way for over 6 years now, I think.:33:

    BTW, there's hardly any fuel in the throttle body unlike a carb, just a pressure spring and diaphragm going directly to the injectors. How long did it run? It sounds like you have an issue with your fuel pump relay. Either wiring or it's bad too.
     
  6. Flurvin

    Flurvin Newbie

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    Unfortunately I believe my truck doesn’t have the oil pressure switch like in the diagram. Only thing on the block in that location is a block heater.

    The truck doesn’t run long with the relay unplugged, maybe a few seconds and very rough. Seems like it just clears whatever fuel is in there. Once I plug the relay back in then it starts and runs fine.
     
  7. PlayingWithTBI

    PlayingWithTBI Desert Old Guy

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    Did you have an oil pressure gauge before? Can you trace it down? You can always install a Tee under the oil pressure switch, then install your sender.

    Then you have an issue with your fuel pump relay.
    1988 Fuel Pump Diagram.JPG
     
  8. Flurvin

    Flurvin Newbie

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    I have been doing some searching on the internet and I think I may have my fueling issue figured out. I replaced the coolant temp sensor on the top of the intake with the one from DD to get my temperature reading.
    This leaves the factory plug disconnected and the ecu flooding in the tbi cause the ecu is receiving a cold reading.
    Tomorrow I will move that sensor to the one between 1 and 3 cylinder and reinstall the sensor on the intake.

    Hopefully this works
     
  9. Flurvin

    Flurvin Newbie

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    Thank you for the wiring diagram. Although your diagram shows only 2 wires on the oil pressure switch.
    My plug on the oil pressure switch has 3 wires.


    70816E5C-8CB9-4CA5-938A-7A6FF9B663E9.png This is diagram I used to get most of the wiring from. Not even sure how the factory gauge received signal
     

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