Oil Pressure Question

[fx4wannabe]

Well I drove the truck to work a couple days ago for the first time in 2 years. Except for running a little hot all was good until on the way home I started losing oil pressure. Ever since I bought it has only had about 10 psi once it warms up but it usually has 40psi cold. Coming home it only had 10 psi cold and dropped to about 5 psi. First I am going to make sure my gauge is reading right before I get too worried. What psi are these things supposed to have? I am reading from the stock location on the turbo. Would running Auto-Rx through it do anything for the oil pressure?

 

[chris142]

cold oil pressure dont mean much.hot i have 38-40 driving 2500 rpm or so and 14-16@idle,it will drop to 12 if its really hot,like after pulling a long hill. using 15w40

 

[FarmerFrank]

Maybe a couple quarts of Lucas would help

 

[jayro88]

Check to make sure the gauge is right first. Is your gauge electric or mechanical. My electric gauge senders don't last too long on my gauge. I think it has to do with the vibration of the engine.

I am assuming you checked the oil level. You can also look into the pressure regulator that is in the oil cooler. It can get debries in it and cause it not to regulate/close properly.

 

[DaytonaBill]

I thought our OBS trucks used sensors that was either 'on' or 'off'... Mine does...

I read here somewhere where you could soldier a certain ohm resistor on the temp gauge and then you could use the pre OBS senders which used a varying signal depending on the actual temp reading.

That's all I remember, sorry...

 

[snicklas]

On the bricknose and OBS trucks, the oil pressure "gauge" is a ~7PSI switch. If you have more than 7PSI of oil pressure, the needle moves to the center of the gauge to give you a "warm and fuzzy" feeling. On the slantnose and earlier trucks, it is an actual pressure gauge, that does move with oil pressure. There are no numbers, but it is not simply and "idiot gauge".

On the brick and OBS cluster, you can bridge a resistor on the gauge cluster itself (not sure which one, but it has been discussed before), and replace the pressure switch, with an older truck spec sending unit. Again, it will move with pressure just like the older vehicles did, but alas, there are still no numbers for reference.

Now on the vans, I am not 100% sure, but I think it is still a "real gauge" up to the body change in 92. I think if it still has the 70's design 3 "pocket" instrument cluster (This was the cluster in the 73-79 F-Series Pickups and the 73-91 E-Series Vans.). I don't think they modded that dash to be an idiot gauge. Just like in the medium duty F-Series trucks with the slantnose dash and cluster, I think it still functioned as a gauge until the major overhaul of the medium duty F-Series around the same time as the F-150, F-250 - F-350 SuperDuty split in the late 90's.....

As far as I know, the 7PSI "gauge" is still what they do today, I know my 03 6.0 is the 7PSI switch........

 

[sjwelds]

^^^which is one of Ford's dumbest ideas ever..................

 

[snicklas]

Agreed..... it is a Warm and Fuzzy that doesn't get the vehicles brought back in for "low oil pressure"..... That is ALL that is.

 

[IDIoit]

^^^which is one of Ford's dumbest ideas ever..................

This is not a big deal, aftermarket gauges are cheap.
IMO the worst things they have done are
A) the F250 pivot differential.
B) deleting the tool box in the bed at the end of the camper special.

 

[fx4wannabe]

I still haven't gotten a chance to check into whats going on but I do have a mechanical gauge. I have never seen more than 10 psi once it warms up. I guess if they are putting a 7 psi switch on them stock then as long as I am seeing 10 I should be fine. I just want to make sure my sure turbo and heads are getting oil.

 

[FarmerFrank]

I'd be checking the bypass in the oil cooler ASAP. I still had 50 psi of oil pressure with 2 spun main bearings in my 4x4 when it **** the bit. Engine had 234k on it with the original oil pump.

Search here about it then pull the filter off and check on that stuff. I'd even replace the oil cooler header if you can't find anything wrong. If that doesn't help I'd think about pulling the engine and replacing the oump

 

[fx4wannabe]

I did some searching on here but didn't find much. Not really sure what I am looking for though. If I pull off the filter what am I looking for exactly? Not sure exactly how the bypass works. I don't have any oil in the coolant or coolant in the oil. I do have 2 spare oil coolers so I can pull one apart to look at it if someone tells me what I am looking for.

 

[79jasper]

It'll be the only thing in the end when you pull the filter off.
http://www.ford-trucks.com/user_gallery/sizeimage.php?photoid=220156&.jpg=

Sent from my SM-T537R4 using Tapatalk

 

[Shadetreemechanic]

Check the gauge before working too hard to diagnose. Swap it out with a new one.

 

[PwrSmoke]

The '94 factory manual lists the following oil pressure specs for a 7.3L IDI fully warmed up with the specified grade (15W40) oil in it:

curb idle- 10 psi
2200 rpm- 40-70 psi

I concur with the recommendation to double check the gauge. If it's a mechanical, you could have a kinked line (been there, done that). Is it 10psi at all speeds including idle? If so, that points to the gauge because if it can only generate 10 at, say, 2000 rpm, then it would be on the zero peg at idle. The bypass is located in the oil filter base. remove the filter and look up at the base. You will see a flat circular doo-daa in a housing staked into the housing. Push on it with you finger or a dull object and there should be some spring tension on it. The IDI has a pretty robust oil pump so even if it were stuck partly open, more than 10 psi is likely... seems to me

Other things to check... massive fuel dilution (such as from a bad injector) can dilute the oil to the point that it's like water. Pull the dipstick, sniff and feel. If it's diluted badly, it could be overfull by a lot as well. Not a common problem but I've seen it more than once (though not on an IDI).

To me, the key bit of knowledge to seek is whether the oil pressure is the same at idle as at a higher speed. If it's the same, that definitely points to the gauge. I would definitely iron this out before driving it a whole lot more. If you TRULY have only 5 psi at times, the engine is not long for the world if you continue to run it.