Oil Pressure
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Mountain Pass
Joined: Jun 2007
Posts: 197
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From: Kansas
Oil Pressure
After spinning a rod bearing and wondering why I didn't see any pressure variations when it went, I find out that the "pressure gauge that's in my dash is not a gauge that would give useful information but just a idiot gauge that might as well be a light. It only gives a warm and fuzzy that you have at least 5 psi of pressure...big deal. I have since put a real pressure gauge on my truck and now need some average base line information that others with real gauges could give me. The book gives a wide spread between 10 and 60 psi. What are people seeing for pressures at operation temp at idle and highway speeds?
Tuned
Joined: Feb 2015
Posts: 333
Likes: 0
From: So. Ca
My 2000 7.3 has a gauge. It shows me a reading about 5/8-3/4 to the max reading, and steady.
I'm assuming that's a great indication.
Can anybody chime in on how that gauge reads equating to psi of actual oil pressure?
I'm assuming that's a great indication.
Can anybody chime in on how that gauge reads equating to psi of actual oil pressure?
Lead Driver
Joined: Jun 2004
Posts: 6,340
Likes: 588
From: Amarillo, TEXAS!
The gauge is essentially an idiot light on a stick. The "sensor" is merely a pressure switch that closes at about 7 psi, so all you can really deduce from it is whether your oil pressure is at least 7 psi or not.
Fleet Mechanic
Joined: Jul 2003
Posts: 1,614
Likes: 22
From: Springfield, PA
In the 2002 SD Wiring Manual (from Tugly's links) it clearly shows the oil pressure sender as the on / off switch you mention. But is the actual gauge in the dash a real gauge? i.e., a 0-5V or 4-20mA gauge? I mean, if we placed an actual pressure sender mounted onto the HPOP reservoir, could we get a real low pressure indication? Does this signal go anywhere else?
Lead Driver
Joined: Sep 2010
Posts: 7,793
Likes: 50
OP...i'll answer your question with my "reading"...pressure sensor mounted on bypass setup, at the frame, pre-pump to be exact. I see 20 at idle when cold, and 30-40psi when running down road/freeway. i do see a varience when engine is warm/idling..anywhere from 2psi to 10psi...go figure.
I think, if i tapped sensor to the hpop resivoir, i think i'll clearly see different numbers. My bypass oil filter is also not a freeflow one. Needs 7psi to open.
I think, if i tapped sensor to the hpop resivoir, i think i'll clearly see different numbers. My bypass oil filter is also not a freeflow one. Needs 7psi to open.
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Mountain Pass
Joined: Jun 2007
Posts: 197
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From: Kansas
Yes, for all of you looking at that factory gauge in your dash, that just telling you, you have some pressure. Has anyone seen it move from it's parking spot once the engines started cold or hot? No. It's not going to tell you that there's a sudden drop in pressure if it doesn't drop to less than 7 psi....Just a warning to people out there that look to gauges for information about the health of their ride. With that being said, I took my pressure from the tap in the left rear corner of the block. I get about 65 psi at idle on a cold start and a steady 50 psi warm at speed. Warm idle speed it runs around 30 psi. Does that sound right to others with aftermarket gauges installed?
Lead Driver
Joined: Jun 2004
Posts: 6,340
Likes: 588
From: Amarillo, TEXAS!
In the 2002 SD Wiring Manual (from Tugly's links) it clearly shows the oil pressure sender as the on / off switch you mention. But is the actual gauge in the dash a real gauge? i.e., a 0-5V or 4-20mA gauge? I mean, if we placed an actual pressure sender mounted onto the HPOP reservoir, could we get a real low pressure indication? Does this signal go anywhere else?
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Mountain Pass
Joined: Jun 2007
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From: Kansas
I think its awful deceptive on Fords part to put a "gauge" in a panel that really should of been just a light.
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Butt-Head
Joined: Apr 2004
Posts: 9,448
Likes: 2,934
From: Reed Point, MT
Originally Posted by puffen:D
I think its awful deceptive on Ford's part to put a "gauge" in a panel that really should have just been a light.
A basic rule of thumb is that the engine oil pressure should be around 10 PSI for every 1000 RPM when warm. If you can maintain that, be happy. But then again, it's all relative. Take a 351M/400 for example. They'll run for YEARS with 2-4 PSI of oil pressure when hot. Oil pressure is overrated.
Butt-Head
Joined: Apr 2004
Posts: 9,448
Likes: 2,934
From: Reed Point, MT
Order up a gauge from your manufacturer of choice.
Use the supplied fittings to attach the pressure line (or sender depending on gauge brand).
Route the hose (or wiring) to the gauge.
Watch the gauge.
Use the supplied fittings to attach the pressure line (or sender depending on gauge brand).
Route the hose (or wiring) to the gauge.
Watch the gauge.
Fleet Mechanic
Joined: Jul 2003
Posts: 1,614
Likes: 22
From: Springfield, PA
Funny guy 
One of these days I'm gonna go out and measure the voltage in the oil sender lead, and the resistance of the sender to ground with engine off and engine running. If I find that the dash gauge will react to a varying voltage, then it *should* be able to work with a true sender, with the correct resistance range. Still wondering if that signal goes anywhere else, I don't see anything in the 2002 SD manual from Rich. Anyone? Anyone?
Having an actual value on the gauge isn't really important as Cody mentioned earlier (I've had one 351M, one 400M, and a 351C in my life, all in Torinos), but if the reading starts fluctuating, then at least you've got a warning that something is going on, and maybe save you a headache somewhere down the road.
Definitely not a high priority item.
One of these days I'm gonna go out and measure the voltage in the oil sender lead, and the resistance of the sender to ground with engine off and engine running. If I find that the dash gauge will react to a varying voltage, then it *should* be able to work with a true sender, with the correct resistance range. Still wondering if that signal goes anywhere else, I don't see anything in the 2002 SD manual from Rich. Anyone? Anyone?
Having an actual value on the gauge isn't really important as Cody mentioned earlier (I've had one 351M, one 400M, and a 351C in my life, all in Torinos), but if the reading starts fluctuating, then at least you've got a warning that something is going on, and maybe save you a headache somewhere down the road.
Definitely not a high priority item.
Thread Starter
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Mountain Pass
Joined: Jun 2007
Posts: 197
Likes: 0
From: Kansas
The gauge that I've installed on my truck is digital in 1 psi increments and it fluctuates quite a bit but at operating temp and at steady rpm it reads a steady reading. I know at 60mph it shows 50 psi and at idle it shows 30 psi. Now if for some reason if I'm going 60 and it drops to 30 I know somethings a-miss and I'll be checking it out ASAP. If I wait until the factory gauge drops to 0 psi, because it has to get under 7 psi, that maybe be the difference between a just a rod bearing and a rod bearing, rod, piston, crank, and maybe a block. But then again you have to be smart enough to know what to look for.
