Recently, when I have started my car, the oil pressure has shot up to and past 60psi. I know this is an electrical problem and not a true reading of the oil pressure just because of the behavior of the guage. After driving a while, the needle drops down and begins reading properly. Has anybody had a similar problem with their car? Which component is the culprit and where is it most likley to be found.
Thanks for your help.

 

the oil pressure sending unit on these cars are known to be unreliable. I'd go ahead and change it.

 

mine have always done that. is it possible that the reference gas in the pressure sensor needs to warm up to give a (more) accurate reading? i just changed the sensor a few months ago after inadvertently breaking it, but it didn't change anything.

 

That's pretty much normal behavior.
When the oil is cold, it has a high press due to its increased viscosity and resistance to flow.

 

that's possible. One thing I forgot to add. This only started happening after not driving the car for 4 months (winter storage) except starting until warmup once a week or two. I don't know what effect this has on the system, or whether it will work it's way out.

 

no hes right, oil pressure is always high until the engine is warmed up, oil is thicker when it's cold and thus you get more oil pressure

 

Trust me. This is an electrical issue. I watched the guage, it was above 60 and not moving at all, even when the engine was warmed up, then randomly when I was driving down the road, the needle dropped down to what it normally reads almost instantly. Does anybody know where the oil pressure sensor is on the 91 model. I know it was combined with the swich, but i don't know exactly where. The component location is too vague in my haynes manual and it's too wet and dark and ...late... out to see for myself.
thanks

 

Most likely it's down by the oil filter. If not then up top near the distributor. I forget which motors have it where. I know my 88 L98 had it up top, and my 91 has it at the bottom.

 

OK, if it drops down instantly, it is electrical.
Look for the sender unit right behind the intake manifold.
To the drivers side of the distributor.
Its piping to the block should almost be touching the intake manifold.
Once you find it, disconnect the wire, start eng and check gauge to confirm that was the right sender. Might try just cleaning the connector with some contact cleaner before you go replacing anything.

 

So on the 91 cars, is there a sensor by the oil filter? if so, what is it's purpose vs. the one next to the distributor.

 

the unit near the filter will be a sending unit/oil pressure switch combo and will have i think 3 wires going to it instead of one. it sends power to the gauge on the dash and also servers as an alternate source for power to the fuel pump if the relay fails. the unit near the distributor is only a sender, not a combo.

 

so what does the unit near the distributor send to? and if my pressure guage is malfunctioning, do I replace that one or the one near the oil filter?

 

you're only gonna have one sending unit either at the top or bottom. my 88 L98 had it at the top and i replaced that when the gauge was giving me erratic readings. now on my 91 i don't have one by the distributor. instead it's now mounted at the bottom and is also an oil pressure switch combo. i ended up changing that one also.

 

this is what the combo unit looks like

 

is your 91 a 305 or 350 tpi?

 

91 350.

http://www.yearone.com/serverfiles/h...p?hid=G14AO169

the second on the list is what I have now near the oil filter. the third is what i had on my 88 350 near the distributor.

 

Thanks for your help:hail: