1st Generation Specific (1979-1985) 1979-1985 Discussion including performance modifications and technical support sections

oil pressure odd-ness

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Old Apr 24, 2013 | 04:35 PM
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wankel=awesome's Avatar
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oil pressure odd-ness

So I was out testing one of the carbs Im currently building for FB's, (more on that later) and I looked down over my gauges during a spirited drive and noticed the oil pressure gauge spiked past 110 psi, pegged to the outside of the gauge.

I stopped alongside the road to look underhood and disconnected the pressure sender...the pressure stayed spiked. Started driving home, and it mysteriously returned to normal. Now, when I start the car it doest read any oil pressure, yet climbs past 0 slightly while im giving the car gas, then returns to 0 at idle.

Grounding the wire causes it to peg every time. Im sure the engine is getting oil pressure bc It should have destroyed itself after a few hours of running with 0 psi.

Any ideas what this can be? I already replaced the sender, am I missing something?
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Old Apr 24, 2013 | 06:03 PM
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79 w 13B4port
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Sounds to me like you may have an intermittant short in the wire that goes from the sender to the guage.
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Old Apr 24, 2013 | 07:15 PM
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Wankel
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Originally Posted by rwatson5651
Sounds to me like you may have an intermittent short in the wire that goes from the sender to the guage.
^This
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Old Apr 24, 2013 | 07:44 PM
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Would an intermittant short cause the oil pressure to read low?
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Old Apr 25, 2013 | 04:03 PM
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79 w 13B4port
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I dont think it would, but it would cause it to spike and may have let the magic blue smoke out of the guage, causing it to be screwy and give erroneous readings. I have discovered that all electronics work because of the magic blue smoke, cause everytime I let it out the device quits working!
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Old Apr 25, 2013 | 04:04 PM
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79 w 13B4port
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Another thing that will cause erroneous reading of the gauges is a poor ground connection.
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Old Apr 27, 2013 | 01:48 PM
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magic blue smoke?
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Old Apr 27, 2013 | 02:34 PM
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kiwi from downunder..
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hes joking blue smoke =dead gauge lol

I would check the wire do a resistence test from cluster plug to the engine bay.sorry if im vauge.
baby in my arms..

and advice above is good to..
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Old Apr 27, 2013 | 02:52 PM
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Figured as much. I actually think i figured it out.

The wire from my condenser grounded out on the engine block, and then it made my gauge readings retarded high. It stayed that way until it burned up the gauge, bc now I can see it moving with oil pressure, just not where it should.. if that makes sense.

When engine is cold, oil pressure reads 10 psi, when warmed up its far beyond 0. Steady increases in RPM and blips of the throttle make it climb to where 0 is on the gauge, then as the engine returns to idle it lowers back to the far left hand indication of the gauge. Like the oil pressure is moving the gauge, but the gauge isnt giving the right reading anymore.
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Old Apr 27, 2013 | 04:12 PM
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Sounds like you let the magic blue smoke out!
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Old Apr 27, 2013 | 04:16 PM
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Exactly. The gauge is now bad, the condenser grounding out caused it, and the only fix for it now is to replace the gauge.
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