Another oil pressure gauge/sender thread

So I bought the truck last year with a non-functional gauge. Replaced the oil pressure SENDER last Fall with an oem unit and the gauge came to life. Old sender looked like it was pulled from the Titanic.

Now this is where my memory gets a bit hazy. I think I recall the gauge hanging around the 1/4 hash mark once at operating temp and sometimes moving to 1/2 when accelerating. After winter it started to make fairly random trips to 3/4. I first noticed it in the Spring after powering up the 800 ft or so of elevation gain in 1 mile on the way up to my off-grid shack. Oil pressure sitting at 1/4 to 1/2 while flooring it up the rise, then moving to 3/4 while cruising or coasting on level ground for the remaining couple of miles.

Last weekend it would sometimes move to 3/4 while stuck in traffic with temps approaching 90 and the a/c on (engine temps via obd2 rock-solid throughout). Another new behavior this past hot weekend was that when I got up to cruising speeds above 70 mph it would sometimes but not always move to 3/4 and stay there. Below 70: sitting at 1/4. As all functioning gauges seem to do, it mostly sits around 1/4. But what if it is trying to tell me something?!

Now my hypothesis is that the damn sender is going out again. The gauge moving to 3/4 not corresponding with increased load (but actually often as rpms and load are decreasing) makes no sense, right?

Some other notes: the truck was missing its splash shield and I never bothered to get one so the thing got sprayed all winter. The engine sounds and behaves completely normally. Not losing or burning oil at 189k. Toyota filters and Mobil 1 synthetic. Gas mileage has been the same since I got it.

I recall seeing a multimeter diagnostic for testing the sender but can't for the life of me find it now. Wanted to do it before posting a thread but alas.... What do you all think?

 

IMHO, your simply seeing normal oil pressure numbers. The FSM shows the below readings one should expect @ idle and increased RPM's

You could also consider installing a pressure gauge for testing if you question what you're seeing.



More than you possibly but Toyota Mechanics has a good You tube channel for various Tundra issues....

 

Yeah, likely no need to be anxious about a reading 3/4 up the gauge. Would be nice if they had psi on it. Maybe I’ll just make believe that 85 psi hits somewhere between 3/4 and 4/4 and be happy my old engine has good pressure.

The two things that are odd to me is that the gauge is acting differently than it was when I first replaced the sender and that the rise in pressure doesn’t correspond with the current load or rpm on the engine. I can blast up a pass and see almost no movement on the gauge, then a see it rising when sitting still in traffic with the AC on. I also drove around all winter with cruise control set at 70 and the gauge at 1/4, but now it sometimes sits at 3/4 at that speed.

if this represents reality then I’d like to learn more about oil pressure. Something about higher outside air temps making it go up?

 

Stupid question, and maybe I overlooked it, but where'd you get the gauge from, and what brand?

 

Not at all. It is Sankei which I think is the OEM.

 

If it were me, I'd look at FSM to confirm the expected resistance, then get an ohmmeter/DMM and confirm it's what you're seeing.

I would assume it should be zero at rest, maybe you'd need the key in ON to test. Not sure.

Based on the video above, maybe it's normal for pre-05/pre-VVTi, I dunno. But I'd be skeptical of the sender.

 

I've been trying to locate exactly that info in the version of the FSM that I have and can't. Last year, before I swapped out my sender, I did see a pdf of that page and remember testing mine. I'd definitely be grateful if anyone could post that info.

Other option is to go swap it at my local NAPA since it is still under the 12 month warranty.

edit: found it. Attached to the combination meter. Just a simple continuity test at the sender end though.

 

I had a run a round with same problem. Turned out to be defective oil filter AND defective oil pressure sender. Don’t buy Wang Chung brand sender.
They don’t work. Buy a good one.