jimep

Just got done throwing a 3 sve in my 91 4 runner that my brother rebuilt. The first time I fired it up a couple of days ago there was oil pressure but yesterday when I went to take it for its first test drive after bolting everything else back up I noticed the oil pressure guage was the whole way down... is there any way that it is possible to mess up the guage in the instrument cluster by running an idiot light sending unit instead of the gauge style sending unit. doing an ohm check on both of them I am getting an infinate resistance reading on the gauge style and a 0 resistance reading on the idiot light style. So I guess my question is will it screw something up by using the wrong style sending unit. I swapped it back to the original one and its still not working. I also tried using a spare 22RE one that looks identicle to the original one and that is also reading o pressure.

MudHippy

One is a "sending unit" the other is a sensor. They look very similar.

An oil pressure sender is used to send the oil pressure readings it detects to a gauge that displays the actual oil pressure. This is done via a varying resistance circuit within the unit itself. As oil pressure increases it causes the resistance in the circuit to decrease(allowing more voltage to be sent to the gauge)and the needle on the gauge moves up showing this change.

An oil pressure sensor senses low oil pressure and is basically just a pressure-sensitive switch that controls the oil pressure warning light in the dash. The switching circuit is closed(warning light is on/resistance is 0) when oil pressure is, or drops, below the minimum safely allowable with the ignition switch on. At all other times during engine operation, providing the pressure remains above that lower limit, the switch is open(resistance infinite) and the warning light is off.

I can't see any damage occuring from trying to use one in place of the other. But, I can't see it working either.



P.S. Try a using a new oil pressure sender. And/or make sure nothing is obstructing the oil flow to it.

jimep

Yea, did that. Pulled it out and cranked it over for a litlle. didn't work. still read 0 on the guage. ran it for a little then did the same thing with the filter and changed the oil while I was at it. still nothing. went out and got the cheapest oil pressure guage i could. fired it up and it went the whole way up past 100 on the start up. Once it warmed up and the idle settled down It dropped down to around 35 so I guess I got good presssure. got a little piece of mind at least now. I guess the gauge is messed up.

toyota4x4907

Where did you get this oil pressure gauge you speak of? I'm in need of one to check the actual PSI, not just the gauge. Is it a mechanical or electrical gauge you used?

jimep

Just ran into autozone and picked up the sunpro one for $12.99. the pipe thread adapter seemed like it didn't want to thread into the block right. I think Toyota uses a British pipe thread in their block which is close but not exactly the same as the standard pipe thread fittings in most kits. It worked temporarily for me to get an idea what the oil pressure was, then I pulled it out. I don't like the idea of having a vital thing like oil running through a cheap plastic line under the hood.

MudHippy

I hear ya, a steel line would be the way to go.

I've got one like yours I haven't installed. I don't have nothing but the gauge itself, no fittings/adapters or lines to work with yet.

'Til then the dummy light is all I gets.