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mechanical or electric oil pressure gauge on TBI

Discussion in 'The Garage' started by az ranger, Dec 10, 2006.

  1. az ranger

    az ranger 1/2 ton status

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    I am looking to put in an aftermarket oil pressure gauge on my 88 jimmy with TBI what are the pros of going with the electrical gauge, is it worth the extra money.
    thanks
     
  2. 1979jimmy350

    1979jimmy350 1/2 ton status

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    are you planning on replacing your stock sensor or adding a adational one? The oil pressure sensor is a integral part of the fuel system, so be carful with what you remove
     
  3. 4X4HIGH

    4X4HIGH 1 ton status Premium Member GMOTM Winner

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    What do you mean by this? I know that the ECM looks for oil pressure for the fuel pump but it is a different switch than the oil pressure gauge switch (at least on my 89 blazer).

    az ranger, i would install a mechanical gauge, more accurate than an electric gauge.
     
  4. 1979jimmy350

    1979jimmy350 1/2 ton status

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    some trucks do only have one sending unit that controls both the gague and the fuel pump circut
     
  5. 4X4HIGH

    4X4HIGH 1 ton status Premium Member GMOTM Winner

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    I thought that was where you were heading with it. At any rate, the switch is only in case the fuel pump relay goes bad then the fuel pump will still work as long as there is oil pressure.
     
  6. az ranger

    az ranger 1/2 ton status

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    I plan on adding an additional one, the stock gauge is not working properly now, and I want to upgrade to auto meter gauges

    do both types of gauges connect at the same point on the back of the distributor.

    how does the stock gauge work is it mech. or electric?
    thanks for the replies
     
  7. 1979jimmy350

    1979jimmy350 1/2 ton status

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    the stock gague is electric, you can add the new one in in the same place by using a adaper T fitting our you can run it off any other pressrure port on the block like down near the oil filter
     
  8. ntsqd

    ntsqd 1/2 ton status

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    FWIW I've never seen anything to support the idea that mechanical gauges are more accurate than electrical gauges. There are those, Gene Berg included, who argue that no guage under $250 is accurate regardless of it's mechanism. I think they are probably right, but not very realistic.
    When it comes to oil, fuel, & coolant I prefer electrical as then you don't have extra possible leakage points.
     
  9. 4X4HIGH

    4X4HIGH 1 ton status Premium Member GMOTM Winner

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    An electrical gauge can become inaccurate as the wire goes bad and starts to have more resistance than when new.
     
  10. neverendingproject

    neverendingproject 1/2 ton status

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    I completely agree, I dont want oil leaking in the cab at anytime. I would much rather deal with wires under the dash. Mechanical will also make it tricky to get the guage cluster out if you have a copper tube attached to the back of it.
     
  11. dyeager535

    dyeager535 1 ton status Premium Member

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    And mechanical pieces like torque wrenches don't need to be calibrated periodically?

    I don't buy into the mechanical aspect either, I'm no expert in aviation, but I suspect 777's and Apache helicopters don't have lines holding fluid running into the cabin to provide pressure readings.

    I won't argue the fact that it wouldn't be a bad idea to check an old gauge against another, but as mentioned, cheap gauges, just like cheap thermometers, have no guarantee they are really accurate either. Not saying they don't work of course, but for the average person to slap a new gauge in the vehicle and just expect it to be 100% accurate would seem a bit naive.
     
  12. az ranger

    az ranger 1/2 ton status

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    So if I understand correctly a mech. gauge will connect at the back of dizzy and run a copper or other hard line to the back of the gauge in the cab

    but a elec. gauge will also hook up at the back of the dist. and the copper line would be replaced with a wire sending a signal to the gauge.

    or I could hook up either at the port near the oil filter.
     
  13. dyeager535

    dyeager535 1 ton status Premium Member

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    At least a couple of taps..over the oil filter there is typically a plugged oil pressure tap, as well as where the stock sending unit is placed. Not sure if the port that is typically found on 4 bolt blocks near the timing cover could be used/accurate.

    It's resistance to ground actually...the pressure is figured out with a mechanical device, however the data is gathered for the gauge via a wire instead of a setup where the pressure gauge is directly hooked to the oil pressure tap, and that moves the mechanism to move the needle. Since a mech gauge goes to "0" when there is no pressure, it means there is at least some sort of spring mechanism that is hooked up, which introduces a source for error, just like wiring.
     

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