Ok so i have a 91 Z28 305, and it runs great, but the problem that i am having is upon start-up, the oil pressure gauge shows is sticking straight up and down at 40...then once she is all warmed up, it pretty much pegs itself into the red...now the idle does not change, the oil burns the same way it always has, and there are no new leaks, atleast not from what i can tell...Now the only thing that I do know needs to be replaced is the EGR Valve, I am just having a hard time finding one that is not 200 bucks...so yea, could that have something to do with it? I just want to make sure that its not something dramatically wrong??? Thanks in advance for anyone's help...

//Eric

 

Chances are your oil pressure is fine and it's a bad sender and/or gauge.

 

That is what I thought...But how would the gauge be bad...I thought it was a mechanical gauge...

 

The gauges are all electric.

 

ok...thanks for clearing that up...so is it cheaper to just by a new gauge, or just replace the whole inlay?

 

I don't know if new gauges are still available. Usually the whole cluster is sold used.

 

ok cool...well you know anyone or anywhere i can get either or...let me know...or should i just get aftermarket?

 

Try the classified boards, or eBay. Nothing aftermarket will be a direct replacement. You'll probably want to narrow it down to either the gauge or the sender first.

 

well if i am correct the sending unit is just above the fuel filter right? if it is there is oil leaking out where the connector is...

 

Above the oil filter, yes.

 

fuel filter......you mean oil filter. my 305 did the same thing, but now the gauge works fine. you can easily see it above the OIL filter. very simple to replace.

 

how easy is it, can i replace it when i do my next oil change? or is it more complicated then that...also do i have to replace the connector?

 

Just unscrew the old one and screw the new one in with thread sealer if it didn't come with any on it.

 

not sure, i am waiting as well for my next oil change to do it. im sure you can look it up on the internet or maybe someone will know how to.

 

ok cool, thanks i really do appreciate all the help, eric...

 

Depends, if it's a single wire connector yes, if 2 definitely not. If 3 wire then it's a pressure sender/idiot light and fuel pump switch combo.

If it's single, or 3 wire check for continuity between sensor metal body and engine ground there should be zero resistance any resistance means that the thread sealer/Teflon tape is interfering with the required metal to metal contact.

My '88 had the sending (single wire) unit behind the right: correction left head next to the distributor, the sensor above the oil filter is the fuel pump switch (2 wires.)

Oil filter has interl bypass valve to relieve pressure if it doesn't open, or open enough oil pressure will build up. I know this from experience and at an inappropriate time, during my cam break in (yes, my block isn't a roller.)

 

Ok I feel really stupid right now...because i know how to do most of the repairs on my car, but I am sure that what you are talking about is very simple, but I am really confused, either that or I am just reading to much into it...please help me get un-confused...

Thanks, Eric

 

Ok, here's a link to a picture I posted of my sensors (can't attach an image already posted.) I have them remote mounted on a common manifold, but should be easy for you to see difference.

It's on the last reply of this thread https://www.thirdgen.org/forums/tech...-pressure.html

 

I have just one more question...do you have to drain the oil in order to change the oil pressure switch...

 

No

 

so when I unscrew it, no oil will leak out...ok cool...thanks?!

 

Some oil may leak out, but it's above the level of the sump so it's not like it'll all come out.

 

ok cool thanks...

 

well replaced the unit...and works great...funny how the simplist things can fix so much...

 

glad to hear it