Oil Pressure
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Oil Pressure
I have an 89 ford F150 and I also have a problem. My oil pressure guage on my dash moves around, when it is cold it is at zero and the check engine light comes on but when it warms up the gauge is in normal. Then after it rns for a while the gauge slowly goes back down untill the check engine light comes back on. Whats the deal
Elder User
Joined: Jul 2003
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From: Weston, Nebraska
Maybe it's your guage, mine never worked right in my 86, said it was low all the time, wouldn't even get to the N on normal, so I put a mechanical in and it has 50 psi. all the time almost. Very good for a 220K engine.
What weight of oil are you running? That could explain the drop after warm up if it's to light, but I don't why it would stay low when cold, my truck when started up runs about 30psi then once it's been on high idle for a little while it's up to 50psi within a minute.
Redneck-Cowboy
What weight of oil are you running? That could explain the drop after warm up if it's to light, but I don't why it would stay low when cold, my truck when started up runs about 30psi then once it's been on high idle for a little while it's up to 50psi within a minute.
Redneck-Cowboy
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Right now I am running 10w 40. I know the guys that I bought that truck from ran 10w30. What do you run, or what do you suggest running. Its realy wierd. It will run about on the M when it is warm but the is slowly declines after about a half hour.
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From: Weston, Nebraska
10w-40 should be good, I'm just running 10w-30. I can see it declining after a half an hour, but it shouldn't to the point that the light comes on. How do you drive the truck? If your in town a lot idling then it might go down, but if your going down the road at a decent RPM it should stay at least for a wore out oil pump 15psi.
Redneck-Cowboy
Redneck-Cowboy
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The oir pressure wil l drop even if it as a steady rpm. But then if I push in the clutch the pressure will go back up. Do you think it has anything to do with the oil pump. I hope not because I think, and correct me if Im wrong, you have to lift the engine off the mounts to swap it.
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From: Weston, Nebraska
Yeah he's right, there's nothing to hooking up a oil pressure guage, it's right on the drivers side between number 5 and 6. All it takes is a 9/16 and 7/16 wrench to put in the sensor. Then hook up the oil line and start up the truck, you can just set it on the fender or something and leave the truck run for awhile to see.
Redneck-Cowboy
Redneck-Cowboy
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From: Charlotte
Check the hose leading from the oil sender to the gauge. Might be a kink in it. Also try going to a larger hose. quicker response.
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Laughing Gas
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From: Parkville, MO (KC)
He said it goes up when he clutches. That's bad news in my books, as I am assuming that the RPMs go up when he clutches. The fact that the guage shows good pressure sometimes and goes up when he clutches makes me think the guage is not the problem.
I think I agree that I'd check the pressure with a different guage once before I replaced the oil pump -- but I think I know the outcome of that endeavor already.
I think I agree that I'd check the pressure with a different guage once before I replaced the oil pump -- but I think I know the outcome of that endeavor already.
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Joined: May 2003
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If I hold my motor at 1500rpm ( in neutral in my driveway) and them floor the clutch the engine continues at 1500rpm. If this is what you are doing (and not driving down the highway) maybe it is a wiring problem being affected by the clutch pedal.
Is there a hose leading form the sender to the dash or is it a wire, I think it is a wire, I dunno. Let us know
There is a mod you can do th the idiot guage to convert it to a useful gauge. It involves changing the sender for a unit of a pre 85 unit ( from a truck with a real electric oil gauge) and shorting out a resistor in the dash gauge ( I serched for the original post but coundn't find it). Maybe someone can remember the details
Is there a hose leading form the sender to the dash or is it a wire, I think it is a wire, I dunno. Let us know
There is a mod you can do th the idiot guage to convert it to a useful gauge. It involves changing the sender for a unit of a pre 85 unit ( from a truck with a real electric oil gauge) and shorting out a resistor in the dash gauge ( I serched for the original post but coundn't find it). Maybe someone can remember the details
Posting Guru
Joined: Jan 2000
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From: Cullman Alabama
Worn center main bearing!
I cant remember the sequence but an old Mechanic told me about the oil pressure going down as you accerlerate, and back up as you lower the RPM and than falling off an a warm Idle.
Get an aftermarket Mechanical guage and you will get the facts.
The Oil pump is usually good at an Idle and low Rpm's. If it's the pump, the delivery falls off as you accelerate and the engine will begin to rattle. It's usually the lifters doing the ratteling, but it can be the bearings too.
Any way you look at it though, a low reading at a warm Idle is a sure indication of worn bearings.
I cant remember the sequence but an old Mechanic told me about the oil pressure going down as you accerlerate, and back up as you lower the RPM and than falling off an a warm Idle.
Get an aftermarket Mechanical guage and you will get the facts.
The Oil pump is usually good at an Idle and low Rpm's. If it's the pump, the delivery falls off as you accelerate and the engine will begin to rattle. It's usually the lifters doing the ratteling, but it can be the bearings too.
Any way you look at it though, a low reading at a warm Idle is a sure indication of worn bearings.
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Hey,
Thanx a lot for your replys guys.
Thudpucker, The engine only raddles when it is cold. After the gauge goes up once it stops raddleing. I actually drove it for about an hour yesterday and it never raddled. But the engine light was on and the gauge was all the way down.
CDHerman the RPMs go down when I use the clutch. Usually at 65 it is at 2500 rpm. So at low rpm hte oil pressure is fine.
76390FE how much do you think a replacemant would cost?
Thanx a lot for your replys guys.
Thudpucker, The engine only raddles when it is cold. After the gauge goes up once it stops raddleing. I actually drove it for about an hour yesterday and it never raddled. But the engine light was on and the gauge was all the way down.
CDHerman the RPMs go down when I use the clutch. Usually at 65 it is at 2500 rpm. So at low rpm hte oil pressure is fine.
76390FE how much do you think a replacemant would cost?
Posting Guru
Joined: Dec 2002
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From: Remsen, NY
I'm pretty sure his gauge isn't the "on/off" gauge on his '89. I think, from the wiring diagrams in my Haynes, that that showed up in 1990. His gauge should actually follow pressure like you'd expect, but it's obviously not very accurate. The sender for the old style stock gauge is a round almost bell shaped thing about 1 1/2" across, this is how you can tell. I don't think he needs the mod for the stock gauge, but obviously a mechanical aftermarket gauge would give a clearer picture.
I've heard that the oil pumps go out of these 300's but I don't understand why? I thought oil pumps should outlast things like bearings and valvetrain parts, there's not that much to wear in them, just gears spinning. Is it true that oil pumps are a common failure in these? Is it because the pickup screens seem to get clogged?
I've heard that the oil pumps go out of these 300's but I don't understand why? I thought oil pumps should outlast things like bearings and valvetrain parts, there's not that much to wear in them, just gears spinning. Is it true that oil pumps are a common failure in these? Is it because the pickup screens seem to get clogged?
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From: NC
oil pump
bhanna4d,just did oil pump swap last month. Have you changed brands of oil lately?My truck had sat a few years before I bought it.I put in fresh oil before a 700 mile trip,and 1 wk later,the pickup tube and 1"in the bottom pan was full of sludge. I got alot of strange oil pressure readings hot or cold ,but lifters rattling was the give away. Only had to jack up motor 5-6 inches.Just make sure you don't stretch the ps hose or fuel hoses too much.It took me about 5 hrs ,mainly waiting for fresh paint to dry,Ford blue of course.Good luck Mark.
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