My 82 has an oil pressure issue. Here is the scenario:

Oil pressure is normal at start up around 35-40 psi. The car warms up and the oil pressure drops. At idle RPM the oil pressure is almost 0 maybe around 3-5 PSI, at 1500 RPM it will read around 20 PSI, at 2,000-3,000 RPM it will read around 25 PSI.

I have changed the sending unit twice. With the first unit I thought to be bad, the needle on the gauge would jump all over the place it would hang out around 40 psi and then tack all the way right to 80 and tack all the way left to 0 psi. I then changed the sedning unit (GP product)and it worked perfect for a few weeks it stayed right around 40 psi, then it would read 0. I removed the wires and reattached them and it worked for a little while the would constantly read zero again. Thought I had another bad sending unit so I changed it (Borg-Warner product). The new unit is reading what I mentioned at the beggining of this thread.

I know the oil is diluted and that can cause low oil pressure but almost zero at idle? I pulled the dipstick and the oil level is full. (the car does not loose much oil) I gave it a good sniff and there is a fairly strong gasoline odor in the oil. I am going to change it and see if the oil pressure improves. I am going to put a thicker oil in the car like 15w-40 or 20w-40.

Does anyone have any suggestions or Ideas what could be causing the probelm other than diluted oil?
Any oil recomendations?

Thanks

Kent

 

The only way to know for sure is to install a mechanical gauge to check it. I can say that I see a few 82s that have gauge problems in my shop. You need to check the wiring from the sending unit all the way to the gauge. There are lots of places that are potential problem areas from the connectors to the printed circuit board.

 

BlueSilver82. A comment on the oil pressure.

When I picked up mine, the PO was using a 10-30w Mobile1. I did notice once the engine warmed up the pressure, at idle, was darn near zero. (which I understand is OK....but......just didnt like that). I switched out immediately to the Valvoline 10w30 VR1 series (I also use in my other cars), and even with the heat around here, it has not changed yet. Stays 37-40 at anything above idle, and never gets below 10. I'm sure if I used their 10w40 or 20w50 it would peg the needle.

On-to-the-gas-smell. You very well may have a bad fuel pump. When they go bad, the diaphram "can" start to leak some fuel back into your crankase. (lets just say I had 1st hand experience on a BB 454). What I started to notice was the smell at first........ when it got worse (and that didnt take long) the oil level was higher.

 

I did have bad fuel pump and I changed it. However it is an electric fuel pump in the tank and not a mechanical fuel pump on the block.

 

Sorry bout' that.....didnt know. (I see you are local to me.............curious as to what oil you are using anyway).

 

What did you mean when you said, " I know the oil is dilluted"?

 

Had a similar issue with my 80 and found that it was a ground issue. Believe the oil pressure sender is just providing resistance to a ground and the meter reads this resistance.... checked and cleaned all of my ground connections and the problem went away... and my fuel guage began to work properly as a bonus.

 

Vettepower.......I think he may be saying that because of the gas smell to the oil.....possibly. (dont know). (my "didnt know" was related to the fuel pump......once past 74' I'm not up on how the cars came equiped for fuel delivery)

 

Check w/ a mech gauge. If your rpessure really was 0 the switch would cut off power to the fuel pump and the engine would stall.

 

If you know you have gasoline in your oil, why on earth are you running that engine? Unless or course you are trying to make an excuse to your significant other that you need/want a new engine! Gasoline is a solvent and negates much, if not all, of the oil's lubricating capabilities. For the cheap cost of an oil and filter change, DO THAT FIRST. Then check your oil pressure.

The obvious things are: proper oil level (too much can cause foaming which acts like a low oil level), weak oil pump, bad gauge, etc. Once you eliminate the proper oil level as an issue, look at the sending unit and gauge.

Gary

 

Marck,

If the wiring is removed from the sending unit wouldn't that send a no oil pressure signal and cut the car off like you said? My car will run with the sending unit disconnected and completely removed from the car.

 

The 12V wiring for the fuel pump goes through the switch and the relay. The relay only makes contact during starting and ign. on, the rest of the time the oil press switch will complete the circuit. Check if your fuel pump still runs without a fuse, if not then the problem is in front of the fuses and only the battery relay and pressure switch are located there. If you pull the black pressure switch connector the fuel pump should shut off

 

I have pulled the black pressure switch connector off the oil sending unit(the wire connector with three prongs ath the top rear of the engine near the fire wall) and the car still runs.

 

also did you use teflon tape on switch threads?really shouldnt do that-can cause bad ground

 

Someone either hotwired your pump directly to the ign. switch. Bypassing the press. switch won't work because the power comes directly off the battery and this means that if the switch was bypassed or the conenctor is shorted internally (not possible) the pump would run all the time, even w/ the ign. off

Did you check if the pump goes on w/ ign. in the run pos and then cuts out, only to start again when ctanking? If you turn the ign. to run and then off again you have to wait about 30 secs for the ECM to prime it again when turning the ign. on.

 

The pump works with the ignition. You can here it prime when the key is turned to the run position.

 

yeah but does it shut off after a couple of secs or does it keep running? If it continues to run it's hotwired to the ign.

 

Shuts off after a couple of seconds.

 

that's how it's supposed to be...weird.

 

Change the oil. GM has a cleaner additive for 10 bucks. Try it. If your tank was gummed up I wondering ig anything else may also be gummed up.

I was running synthetic and noticed my pressure was low...maybe 14-15. I had the system flushed. I changed the oil to factory spec and had the cleaner put in. I'm 20 at the low end now with about 42-45 on the high.

With you reading zero I suspect the problem is something else but try the basics first...

Are you getting a ping on excelleration? Or valve chatter?

Jim