oil pressure gauge weirdness

nikkievix

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heres my issue. when i turn the key on, the oil pressure gauge shoots up to 40 psi and stays there, when i start to crank the engine, it bounces between 20 and 40 psi, when the engine is running, it doesn't move till i turn the electrical off. gould i have a bad gauge or sending unit? if it's the sending unit, can i use an automotive one?
 

Scott Danforth

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I would check your wiring.
could be the sender, you can check with a digital multi-meter
  • Zero pressure = 240 ohms
  • 1/2 gauge reading = 103 ohms
  • full gauge pressure = 33 ohms.
you can use any sender you want if its a 240-33 ohm sender
 

nikkievix

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thats for the fuel......my issue is with the oil. but i'll check the wire and see if i got short in it.
 

Scott Danforth

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same 240-33.5 ohm style gauges

guess what your water temp is too
 

sam am I

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If you don't see a wiring issue right off the bat,

As a static test of the gauge you could always use a jumper wire and short the "S" terminal to ground and deflect the needle fully.....but that can give a indeterminate at times depending on how things are failing,

If the water, fuel and oil all have same/similar resistive curves as per their respective temp/level/pressure as Scott has indicated and you want a bit more of a linear test (less having a potentiometer in the kitchen drawer like myself), then as a trouble shooting aid, I'd be inclined to be swapping a "S" wire from a known good sender (water, fuel) to eliminate or confirm a suspected bad gauge/sender (oil)........

For example, if the known good sender (fuel) is used and you have a half tank of gas (approx 100 ohms), you should read *50 psi of gas in the tank ;) connecting the fuel sender's "S" wire to the oil pressure gauge "S" terminal. If confirmed as such, this would be of course indication of a bad oil sender (or wring path).



See "fuel" and "oil" details/resistance values in the below images.

*assumes the oil gauge is a 100 psi full scale

TMTechCat-Instruments(v4_0)Tech Reference_Page_06.jpg TMTechCat-Instruments(v4_0)Tech Reference_Page_07.jpg
 
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nikkievix

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the water temp works....have to touch the connector remains to the terminal on the sending unit...need to replace that. the oil pressur sending unit seems plugged, sprayed carb cleaner in and a bunch of crud poured out, had a little better reading on the gauge...this time was 40 psi key on engine off, crank and the pressure moves to about 50psi and when running was about 80 psi...tells me the sending unit is shot. turn the key off and the gauge dropps to the left side like it should. so....i'm just going to replace the unit and wondering if an automotive unit for the chevy 153 would work.
 

nikkievix

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ok, i found one for a 1966 chevy II 153 4 cylnder..should be the same, i'll research it since the store has it for $11 for an AC delco brand.
 

sam am I

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Be sure you're not mistakenly installing (or replacing) a "pressure switch" rather than a resistive type "pressure sender" as it appears from the above dialog/s your gauge type requires/is.

The link below for the 66 153 is appearing to be showing only switch's, these obviously aren't made for your type analog gauge.......just say'n. Switches run lights/buzzers, senders run gauges/needles.

http://www.oreillyauto.com/site/c/se...make=Chevrolet
 
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Scott Danforth

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ok, i found one for a 1966 chevy II 153 4 cylnder..should be the same, i'll research it since the store has it for $11 for an AC delco brand.

you have to look at the resistance range, not what it originally came on. automotive may or may not be the same. there are about 10 different resistance scales for gauges that are used.

any 240-33.5 ohm sender will work. the 1966 chev ii with the 4-banger did not come with an oil pressure gauge only an idiot light on the dash.

skippy behind the counter at autozone wont be able to look up gauge senders by resistance code. go to NAPA or order on-line

http://www.iboats.com/Boat-Parts-Ac...-filter.prod_name?q=oil pressure sender&s=sol

use the forum code forums5 to save 5%

or do a google search https://www.google.com/search?q=240...+pressure+sender&safe=off&channel=fs&tbm=shop
 

nikkievix

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i put in a sender for a 1966 chevy 2 153 4 cylinder, turned the key and the neddle rises from the off position to 0, crank the engine and needle comes up to about 10 psi and fires up and stays at about 35 psi at idle and WOT hits a little under 70 psi. so it works now and have good pressure...basing the pressure readings on my 87 mazda B2000. when i drop back to idle, the pressure comes down at a reasonable rate. thanks for the advice and tips guys.. i know i may not follow instructions and advice alot...but i do appreciate the input :) now on to figuring out what to do for a fuel gauge...its sending unit works..been tested, but the gauge i wanna say is trash. gonna eventualy replace all the gauges and install a tach. so fuel gauge is gonna be first....thinking nice VDO brand :) get a dual gauge with a fuel level and temp in one unit, install an ampmeter, new oil pressure gauge and a trim gauge then a 4.5 inch tach. wanna do black face with blue back light and white needles. so..now...how to wire up an ampmeter in to a GM marine single wire alternator.
 
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