Oil Pressure, Weight

[Chris28]

I think my oil pressure is too low. Actually, I know my oil pressure is too low...way too low. Cold start is around 20 psi per 1000 rpm, so it's usually around 55-60 while I'm cruising. Once it warms up it's around 10 psi for every 1k rpm, so I cruise with it around 30 psi. Now if I drive for more than say 45 minutes, the pressure drops way down. On the way back to school (about a 4 hour drive) I would look at it every now and then and notice that the pressure was always less than when I last checked. By the time I was within a few miles of school it was about 20 psi at 3k rpm, and once I got off the highway it idled at like 1 psi. Even if I tapped the gas I didn't see a change in pressure, it wasn't until about 2.5k rpm that it even got above 10. By the time I got to my apartment it was like 15 psi at 3k rpm, and it didn't even show any pressure at idle. I drove it a few hours later and the pressure was back, but by the time I reached my destination about 30 minutes away I noticed the pressure pretty low again.

It's probably been about 1800 miles since my last oil change, I'm going to change it asap. Right now I have Wal-mart brand 10W-30 in there, I'm thinking about upping the weight so it's thicker and keeps my pressure up. I haven't driven my car very hard since the last oil change. Granted I did go to a track event, but I only got about 10 laps in so it's not like I was hot lapping the car all day.

I don't think it's my pump since the pressure is fine at cold startup, so I'm guessing it's the oil. The oil level is fine but the oil looked a bit dirty, could dirty oil affect the pressure this much?

Thanks for reading the wall of text, I always seem to have the most basic questions and I end up writing a freakin' novel haha.

[biggie]

With Mobil 1 10w-30 in my ka-t I'm at 45-50psi on cold start up at cold idle (1k rpm), 20-25psi at warm idle (600-700 rpm). Around 55psi at 3k rpm when warm.

Something seems off on yours for sure.

[Chris28]

Alright, thanks for the guidelines. I know I need to change the oil but I'm wondering if there could be anything else that would give me such low pressure. The pressure sender is less than a month old, and the gauge itself is about a year old, neither of which I think are bad. The way I described my pressure was pretty vague, here's a better explanation.

Cold idle 1000 rpm (first five or so minutes): 55-60 psi
Warm idle 700 rpm (five to 20 minutes): 35-30 psi
After driving for a while (30+ minutes): 30 psi at 3k rpm, 10 psi or less at idle, falls off from there the longer I drive.

[biggie]

This with boost again? Or you still NA?

Maybe the oil just sucks and/or is getting too hot.

[Razi]

Definetely way too low, Chris.
When I'm fully warmed up, I have a little over 20psi at idle.

Then I have about 50-60 psi at 3k rpm, full warmed up.
I have 10w-30 weight AMSOIL synthetic oil.

Maybe your oil pump is on it's way out?

[Chris28]

Yeah boost is present haha. It's possible that the oil is getting too hot, but I've never really had a problem before. I'll change the oil and see if it changes anything, chances are it will. I did use teflon tape instead of paste on the fittings, maybe it's blocking some oil from getting to the sender, but that wouldn't explain the normal pressure I see at startup and for the first few minutes of driving.

[biggie]

Didn't use anything on the sender did you? Most cases any sealant on the sender will hinder it.

[Chris28]

I did use thread tape on the sender, I'll check that as well.

[Chris28]

Alright, I changed my oil today as well as checked the pressure sender, and my oil pressure it still low. 40 psi on cold startup, 20 psi from 5-10 minutes at idle, and by the time I got back to my apartment complex it was idling at 1-2 psi.

When revving the engine the highest I ever saw was 40 psi. Anything above 2500 rpm and the pressure stayed right at 40, meaning I have a leak somewhere in the oil circuit. A friend suggested a stuck open oil squirter. Could this be the case? I'm looking at the FSM and it's possible that the spring in my oil pump snapped, or the regulator valve isn't closing correctly. The fact that it just stops building pressure at 40 psi no matter how many revs I give it is a definite sign of a pressure leak, but can anyone think of anything else that it might be? Can oil squirters really just get stuck open?

Either way I need to fix it before I drive it again, which possibly means a re-build.

[Razi]

Hmm, I was under the impression the oil squirters were always open, just a little pipe that's tapped into the block and aimed towards the piston.

I'd think it's more the oil pump's fault for the low pressure though.

Either way, I guess you'll have to take stuff off the engine and check out the oil pump and squirters.

[Chris28]

Yeah that's what I thought as well, but a friend of mine with a Supra said Toyota and Honda engines have a ball and spring mechanism inside so they only squirt at a certain oil pressure.

Regardless, I need to start tearing things apart to see what's wrong. I'll see if parents can dig the front cover/oil pump out of my parts pile in the garage and ship it to me, I'll take that one apart and re-build it with oem stuff to make sure it works then switch it out with the one currently on my engine.

I haven't seen the oil pressure idiot light come on yet, but I don't know at what pressure that comes on. Maybe I'll convince a friend to let me borrow his gauge to see if it's my gauge that is messed up.

[biggie]

Stock warning light is like less than 10psi or something I think.

Definitely seems like the pump or the pick up is clogged/blocked.

[Chris28]

Yeah I figured I would have seen the dash light come on, but it's either broken or my gauge is messed up.

Here's my most recent thought: the sender measures resistance and sends that info to the gauge via the signal wire. Since it measures resistance, the gauge/type of wire going between the gauge and sender has to be the same to ensure that there isn't any variable resistance. Say that during my last engine swap I just used like 4 different lengths of different types of wire spliced together when re-connecting the signal wire...one of those wires happens to be a huge 10 gauge wire. Since there's less resistance in thicker wire it could be messing with the signal being sent to the gauge, thus messing up the reading.

I'm about to run to Radio Shack and grab some wire that's the same as the original gauge's wire, maybe this is what my problem is haha.

[motoman399]

i have been following this a little bit... i really dont think its the gauge of the wire. i think the sender is a switch more than a resistance thing. i believe that when it gets too low of psi it grounds out the switch. meaning on one side of the bulb you have power and on the other side (the ground) it goes to that pressure switch and when low pressure occurs it cuts off.

try putting on a new oil filter and on first start up see if the light comes on. it always does for me right after an oil change.

[Chris28]

I'm talking about the sender for my aftermarket gauge, not the stock dash light sender. I don't think I've seen the dash light come on ever, even after an oil change. I'll check to see if that's working correctly while I re-wire my aftermarket sender.

At 1-2 psi of oil pressure I don't think the engine would run as smoothly as it does, but I'm not assuming it's the gauge until I ruled out every other possibility.

[Chris28]

False alarm everyone. I re-did the wiring and now it works. The ground for the gauge somehow got un-grounded, not sure how it was getting the readings it was showing. 20 psi at warm idle, 65 at cold ide, and it was around 40 psi cruising at around 2k rpm.

Thanks for the help/support, it's always the little things.

[Razi]

Yay!

[breadbox]

Good that you don't have to drop the pan now.

[motoman399]

lol good deal. hope your soldering everything

[Spring Break '92]

So Chris, does this mean you are coming out to DW8? I'll see you there if you go dude. Im STOKED about this.