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WakeWorld Discussion Board » >> Boats, Accessories & Tow Vehicles Archive » Archive through November 17, 2003 » Oil Pressure: Guage or Sending Unit? « Previous Next »
By Craig Fulton (oldschool) on Tuesday, October 28, 2003 - 6:57 am:    Edit Post Delete Post
The guage just fizzled out. It had been jumping around for a while, now it's dead. The oil pressure is good though.

Wonder how I can tell if it is the sending unit or the guage that has died on me. Do I hook an ohm meter up to the sending unit and check for a reading? No reading=bad sending unit? Any reading=bad guage?

Thanks all!

 
By notidad (noti_dad) on Tuesday, October 28, 2003 - 1:53 pm:    Edit Post Delete Post
Gauges don't usually go bad unless there's condensation or something under the glass. Chances are it's the sending unit. Make sure you use one from your dealer that was made for that engine type. Parts stores carry sending units but they're usually generic for many gauges and sometimes give false reading eventhough they are new. That's been my experience.
 
By Phimple (phimple) on Tuesday, October 28, 2003 - 2:16 pm:    Edit Post Delete Post
Sometimes you can short out the sensor wire to see if the gauge goes up, if it does then its the sender, if not well it could still be either.
 
By Psyclone (cyclonecj) on Tuesday, October 28, 2003 - 9:25 pm:    Edit Post Delete Post
The sending unit is a strain gauge. A rubber diaphragm with a resistive element glued to it. As the pressure from the oil stretches the rubber, the resistance decreases. If you pull the wire off the sensor and short it to the block, the gauge should go to full range (ignition on or gauges powered) If not, it is the gauge. If so, it is the sending unit. They are calibrated differently for different engines, and versions of the same engine. They are a high failure item due to heat, pressure and vibration. Gauges rarely fail, sending units fail frequently. In a pinch, anything that fits will do, all you really care about is notification of a total loss of oil pressure, not a constant, accurate or relative measurement. My Toyota requires over 100 psi of oil pressure to actuate the advance mechanism on all 4 camshafts based on engine load. The sending unit screws up regularly, I am on my 4th. No biggie, it has nothing to do with engine condition, it's just an indicator.
 
By Craig Fulton (oldschool) on Wednesday, October 29, 2003 - 1:22 pm:    Edit Post Delete Post
Thanks Psyclone. I'll try to short the wire to the block and see if it jumps. Basically, shorting it to any ground should give me something I presume.
 
By Psyclone (cyclonecj) on Wednesday, October 29, 2003 - 4:58 pm:    Edit Post Delete Post
Short it to the body of the sending unit, that is the ground path normally as it is screwed into the block. The gauge should go to full pressure or thereabouts.
 
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