This applies to the oil gauge-equipped tach clusters for 84-88 trucks and 84-89 4Runners.

Matching the general consensus, my oil gauge bite the big one. I read just a smitch above the 1/4 mark at cold, high idle and at the bottom with warm idle.

There have been a few posts on related issues with these devices, but with no helpful results other than "it's just that way". To me this is unacceptable. My '73 Z car electric oil gauge works flawlessly and is 11 years older. The mechanical tripod gauge setup on my inclinometer is view blocking and hoaky. So I'm setting out to find the primary responsibility for the defect of the stock oil gauge.

I have tested my sending unit via a 5 watt light bulb. The bulb dimness varies with engine speed, suggesting a rise and drop in oil pressure. CHECK.

According to the FSM, the wire to the sending unit should supply roughly 4.5V to the sending unit. FAIL. It supplies 12V.

Due to this mismatch, the next step is to measure resistance between posts A & B (as labeled in the FSM) to read resistance values. Anything not closely related to 44 ohms equals a default "receiving unit" ala oil gauge.

I will be testing the resistance late tomorrow and will post my findings. Following my pre-estimation that this gauge unit will be labeled BAD, I shall proceed to the junkyard for a suitable replacement.

 

whats the gauge do? mine seems to always rear about 1/4 unless reved past 1800 which it goes to about 1/2
thought this was odd because my a/m gauge on my 94 always read ~70psi which i thought was high, but this is also a turbo motor so maybe 70psi is only 1/2 way up lol

 

See mine drops to the bottom at idle. I have never seen my stock gauge even MAKE it to the half way point. That's how bad it reads. It's not oil pressure because my mechanical gauge reads 50psi at warm cruising and almost 80psi at high idle cold.

I intend to finish this diagnosis but it'll be a couple days. Got a lot of projects going on right now. Need to find time to pull the gauge cluster out, maybe tomorrow.

 

Any progress on this? I have the exact same problem. Sending unit tests ok with the bulb test and I gots 12v coming from the gauge.

 

Where'd you go off to ?????

 

i know how to fix this, but it's ugly....


install an aftermarket oil pressure gauge, that has an oil line running to the back of it. lol

 

i think our trucks have less than 10psi of oil pressure at warm idle (750rpm)

i heard that somewhere on here..from an FSM

 

Nope !!!! Put the SR5 cluster in there for a reason and I'm going to make it work dammit !!!! Put my manual gauge on there a bit ago and have 25PSI @ hot idle (800RPM), and 78-80 @ 3000 RPM. That is with a thin 10w30 in there on a 350k mile engine that has not been opened up yet !!!!

 

So, anyone have a known good gauge from a SR5 cluster in good shape ?