No Oil Pressure 89 f-250

The other day my oil pressure game went to low. and you can tell it's not getting oil because you an here it in the motor. Sometimes when i first start up the truck it had oil pressure just fine. After driving
for 10 or so minutes it drops to nothing. But if i shut off the truck and start it back up it goes right back to normal.
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Less time lookin for nookie, more time on maintenance?! ;)
Clues may exist on dipstick and oil filler cap.
Foamy light chocolate? Black Sludge?
--
Yeh, I'm a Krusty old Geezer, putting up with my 'smartass' is the price
you pay..DEAL with it!
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ncrocket wrote:

I'm not sure just when Ford went from a "real" oil pressure gauge to a idiot light with an analog readout, but it probably was late 80s for the truck lines. If there's a button type sender at the oil pressure output port, it's a fake gauge that closes a switch around 7 psi and then reopens it at say, 5 psi. Put a mechanical gauge on the oil pressure port and see if the readings are consistent with the factory "gauge". If so, you have problems, ranging from a dirty sump (oil pickup screen gets clogged) to worn main bearings or crankshaft. If not, it's the gauge itself, the sender, or the sender wiring.
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Since the late 60's at least, '71 for sure.
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351CJ wrote:

No, they had idiot lights back in 1949 or so; I'm talking about the fake gauge that's driven by an on-off switch like the idiot light, but appears to be an actual needle-type gauge. That piece of trickery didn't happen until the late 1980s on Ford trucks, and Ford-made cars with apparent gauges in the early 1990s.
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Well I have an '82 pickup or bronco, or an 89 pickup, take your pick, with a factory idiot GAUGE, not the light! If you need a picture the gauge and it's sending unit, I'll gladly post if on a binary Usenet group for you. I don't have my 71 truck anymore, The oil pressure gauge in that one may have been after market.
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351CJ wrote:

Check the sender on the '89. It's most likely the button-type, and the "gauge" in the cab is a fake. If it is a button (snap-switch) sender, look at one of the Ford truck websites for a how-to conversion to a real gauge, or if it doesn't bother you, do nothing.
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ncrocket wrote:

Oil pickup screen is plugged.
For some reason, quite common on the 5.8/351.
I'll bet that's your engine...?
Rob
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With the audible noise, likely the gauge is NOT lying to you. As another poster told you, probably sludge is being sucked up to the oil pump pickup screen & causing engine to starve. Shutting off engine allows sludge to 'fall away' from the screen & let pressure go back up when you next start it--then the cycle repeats. Some will say to have pan removed, remove & clean/replace screen/oil pump/oil pan. Much quicker, cheaper, and quite effective procedure would be to drain oil on Friday evening. Replace plug. Pour in 4-5-6 qts.--equal amount to # of qts of oil it takes-- of carb cleaner (the kind that is used to soak entire carbs in). On Monday evening, drain oil pan COMPLETELY. This brings out now-diluted sludge along with the carb cleaner which has now washed the pan & oil-pump screen and to some degree, the pickup tube. Replace plug & refill with oil and change oil filter too--just to say you did. Drive truck for few minutes until it reaches full operating temperature, bring it back and change oil & filter again IMMEDIATELY WHILE STILL HOT. Problem solved! It works, I know, 'cause I've done it several times! Donate $ saved to your local church/charity. s
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