308 Oil psi Gauge - Ferrari Life
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post #1 of 8 Old 09-18-2004, 04:16 PM Thread Starter
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308 Oil psi Gauge

I have a 1980 308 GTSi and am wondering about the oil pressure sending unit and the pressure gauge. My car runs like a top, good power, doesn't use very much oil at all, but the oil pressure seems to show a bit off??? The gauge is a 0 - 85 - 175 lb version, and the warning light works, so I'm not really concerned that I have an engine problem but the gauge never goes above 85. It mostly runs about 65-75, but when the engine is at full temp and at idle it's hardly above the 0 mark. Is this gauge just way oversized (i.e. the range is to large that the pressure will always appear at the lower end) is my gauge bad, how about the sending unit??? Couple of questions for you pros. Thanks

1980 Ferrari 308 GTSi
2002 Mercedes Benz C32 AMG
2004 Triumph Bonneville - Cafe Racer
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post #2 of 8 Old 09-19-2004, 07:32 PM
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From memory (and for the 328 motor) the pressure should be 75-83 psi at 6000rpm, FULLY warmed-up (= oil temp around 200deg F ?). If below 65psi at this speed then you have a problem to be addressed.

I will check these numbers tonight but it looks like the gauge just is over-scaled.
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post #3 of 8 Old 09-20-2004, 02:17 PM
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OK, the numbers for a 328 are:
Oil pressure to be between 71 & 85psi at 6000 rpm with oil temp 212 degF.
If less than 64 psi under these conditions then back off & get it checked out. Note: this is for a wet-sump engine.
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post #4 of 8 Old 09-20-2004, 04:00 PM
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As a note the 3 series oil gauges are notorious for being mis-calibrated. You might want to pull it and have it recalibrated.
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post #5 of 8 Old 09-22-2004, 05:34 PM
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I took the oil pressure sender out of mine and hooked up a mechanical pressure gauge in it's place. I then performed a test from cold start up to full temp, at idle speeds and up to 6,000 RPM. I recorded all of these numbers in my record book.

I now know exactly what my engine does at any tempurature and RPM. I calibrate my eye to compensate for the inaccuracies of the OEM gauge.

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post #6 of 8 Old 05-15-2005, 09:58 AM
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oil pressure gauge

I have a similar problem with mine too. Sometimes I have about 85 while driving then down to about 0 at an idle. Sometimes someplace inbetween. Then it will switch and I'll have just above 0 at speed and about 85 at an idle. It can't seem to make up its mind. The red light never comes on. And if I look in the oil filler cap I see good oil flow. And she runs like a top too. All temps. oil/water stay fine too. If I tap the sending unit with a screw driver the pressure goes back up to around 85 again. I think the culpret is the sending unit. If you replace yours, would you be kind enough to let me know the results. I have yet had the time to replace mine. I'm 99.9% its the sending unit, but that .1% still eats at me!


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post #7 of 8 Old 05-18-2005, 01:09 AM
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The sending units on the gauges are well know for being problematic. Do you have any other reasons for being concerned ?
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post #8 of 8 Old 05-18-2005, 01:20 AM
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Identical problem with mine. I replaced the sending unit with an aftermarket replacement (much cheaper than the original). The gauge worked properly for about a week until the replacement sending unit failed. I've been living with it but I guess one day I'll have to get the original replacement unit. At least I know what the problem is. And like you guys said, the red light does work. I verify that every time I start the car.

Capt. Pete
'79 308 GTS, '82 Jeep CJ7 Jamboree
"Time is what prevents everything from happening all at once."
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