When turning the vehicle off, is the oil pressure dial supposed to drop down to 0?

...mine stays at the last position it was in while the car was running. And when the key is put in the ignition and turned to ACC all of the other gauges spring to life while the oil pressure dial then drops to 0.

Vehicle turned off (the oil pressure was low when turned off -- if it had been at 40 the needle would read 40 in the below picture):



ACC position:




I'm trying to troubleshoot my low oil pressure problem and have a good feeling it's just the oil pressure sender. Curious if this was a sign affirming that...


Thanks!

 

Does your oil pressure read constant when driving

 

No, it moves around (not erratically).

On a cold start the gauge will read 40psi and slowly drop from there as it warms up.

I haven't driven the vehicle in three days since I noticed the oil pressure being on the low side and the "check gages" light flickering on occasion at full stops -- don't want to risk damage.

I looked around by the distributor and think I see signs of wet oil by where the oil pressure sender would be, so i'm hoping that's the cause of my problem.

 

if it gets low enought to illuminate the check gauges light in could be a problem, but the gauge staying where you leave it when you turn the key off is normal.

 

Thanks, Andrew! That's what I was curious to know...

 

When the ignition is in the RUN position, engine running or not, the dash gauge will indicate the oil pressure. When the engine is running, and you shut it off, the gauge will continue to indicate the last reading before the ignition was shut off. Yours is working as it was designed to. As for accuracy, you'll need to install a manual gauge to test the oil pressure and compare it to your dash gauge.

 

If your oil presure is only running at 40psi at start up its on the low side.If the engine has no problems with brearings or anything it should start up at 60 psi cold and run about 45 or psi.The 4.3 can run safely at lower oil presures.I had one in my van that would run 25psi engine hot and start at 50 psi cold.Mt 94 gmc truck starts at about 58 psi cold and runs at 45 psi hot.Hopefully its just the sending unit and not the intake manifold leaking.Also could be a valve cover leaking also with the oil dripping back behind the engine.

 

Thanks for all the responses!

It's actually my brother-in-law's truck, so i'm not able to confirm what the oil pressure has read in the past, but it's definitely reading 40psi from a cold start now. It's a 2000 4.3L V6 4x4.

I picked up a new sending unit this afternoon and will attempt to install it tomorrow. Hopefully that does the trick. If not, i'll be sure to pick up a manual gauge to get a better understanding of what's going on.

As far as oil leaks, I haven't seen anything too obvious or concerning. And I've spent a good deal of time poking around this vehicle from all angles these past few weeks, putting new brakes on it and dropping the fuel tank to install a new fuel pump, etc... I'll be sure to give it a good once-over while i'm working on it tomorrow.

Thanks again!

 

Some hints: at the very least the distributor must come out to even see the oil pressure sensor much less remove it. And a pathway to take the dist out is required, so ignition module, coil, evap relay, etc will likey need to be removed.

That oil pressure sensor is at the very back of the intake, under the fiewall. I can get to the one on my Corvette easier than the one on the Blazer.

Have plenty of "Band-Aids" available for numerous scraps and cuts.

Good luck on this one. Might be a good time to put a new cap and rotor in, perhaps plug wires too.

 

If the spring in the oil pressure bypass valve gets weak, it will cause oil pressure to be low. Pretty simple to replace or "tweek" the pressure up a bit. Remove the oil filter adapter, (rear of engine where the oil cooler lines attach). Remove the bypass valve and either replace it, (under $10) or put a washer under the spring to increase the spring tension.

A leaky intake manifold gasket will not cause a drop in oil pressure, unless it leaks all of the oil out