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Oil Pressure Issue

 
Old 07-06-2013, 09:25 PM
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Hey All,
I have a 94 F150 4.9 with serious gremlin issues!!!! Most pressing, my oil pressure gauge "works" intermittently. In short, I replaced the pick up screen in October due to low/ no pressure and tons of carbon build up in the motor. The screen was completely blocked so I installed a new one. Afterward, the motor showed no oil pressure so I parked it until this week. Low and behold after a jumpstart, the pressure was fine.... for a day. the next morning, no pressure. Turned the truck off then back on and it worked fine. Today again, no pressure and no amount of off/on fixed it.
I checked the oil both with the engine off and running, and there is oil on the dipstick which does run higher up the ds while running. Also pulled the filler cap and can see oil on the tops of the valves. Shut it down and let the oil drain back to the pan. Checked valves again and there was no oil standing on them. Restarted truck and oil was again present on the valves and I watched it "seep" across the space between them.
Question is, how much pressure should be flowing over the valves? And what could be causing the flightyness of the gauge? Bad pump, bad sending unit, bad connections, or bad gauge? I've read a mechanical gauge is the best way to check the op but have no idea where to hook one up. Also read/ heard a higher weight oil might help and that the oil filter could be the culprit....
Help?
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Old 07-06-2013, 10:22 PM
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Do yourself a favor and pick up a manual oil pressure gauge from Autozone or another parts store, install it and check your oil pressure the old fashion way. I have had two older model F-150's that for some odd reason began having the same symptoms. One was a '78 model with a 351M and the other is my '93 Lightning. Changed the sending unit on both and it did not help. Installed a manual (liquid, not electric) gauge and found the oil pressure was fine. Problem actually seems to be the gauge in the dash. Hope this helps.
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Old 07-06-2013, 10:36 PM
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chance is about 99% the sensor switch is bad or the wire connection is oil soaked and loose as stated above the best solution is install a mechanical gauge to learn your true oil pressure That thing on the dash is not a gauge it's just a idiot light with a pointer that tells you there is some oil pressure when its working it always reads the same regardless of actual pressure
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Old 07-08-2013, 04:34 PM
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Thanks for the tips... Installed a manual gauge now I'm wondering what the "normal" range is. I'm fluctuating between 30/35 in park and 25 idle to 45 accelerating.
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Old 07-08-2013, 04:48 PM
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Originally Posted by DadsOldTruck View Post
Thanks for the tips... Installed a manual gauge now I'm wondering what the "normal" range is. I'm fluctuating between 30/35 in park and 25 idle to 45 accelerating.
That's well within normal range.
You will note the pressure will vary with oil temp but even if it drops to 5psi at hot idle you are good to go
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Old 10-26-2017, 07:58 PM
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Hey everyone. I have 94 f150 I bought recently. It didn't run when I bought it. It needed a new head and gasket. Did all that and have it running but it has very low oil pressure. It's not totally out of the normal range but is very close to it. I'm wondering if something i did putting the head and everything back on could cause this. Or if it's just the oil pump
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Old 10-26-2017, 09:05 PM
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Does your oil pressure gauge actually ever move once the engine is running? If you have a real working oil pressure gauge it will move with engine RPMs and engine temperature.

These just come with an idiot gauge that goes up to some point in the normal range of the gauge as long as you have adequate oil pressure. That " some point" may be at the low end of the normal reading on the gauge. If you don't have adequate oil pressure the gauge will go clear to the left.
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Old 10-26-2017, 09:12 PM
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It has the typical stock gage that has the word normal
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Old 10-26-2017, 09:15 PM
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Originally Posted by Dbford94 View Post
It has the typical stock gage that has the word normal
Then I assume the gauge never actually moves once the engine is running?
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Old 10-30-2017, 03:48 PM
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It moves from the L to just over the normal line on the Guage.
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