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Oil Pressure Light On After Timing Chain Replacement

S

Scott Kane

New member
Just recently did the following:
-Timing Set w/ new gaskets
-Water Pump w/ new gasket
-Oil Change 5qts 10w30
-Belts
-Hoses
-Tensioners
-Coolant Elbow
-SC Coupler

I packed the oil pump gears with petroleum jelly prior to reassembling. I was sure to install the oil pressure relief valve and spring correctly. All galleries were cleaned while disassembled. It did sit for a few days with no oil while everything was apart. I did turn the motor by hand (without oil) a few times when checking the timing set. Just for clarity, I never started the motor without oil

After reassembling everything, I cranked the motor and let it idle while checking for leaks. Initially there was some chatter while warming up. Found a few coolant hoses that needed tightening. Turned the motor off. Tightened up loose hose clamps and moved the car outside. Only the low coolant light was on at this time. While I let it continue idling outside, I replaced the windshield washer pump (~5min or so). At some point while doing this, the oil pressure light came on. I noticed it would flicker some and then stay illuminated. Not wanting to damage anything, I killed the motor when I noticed the light. Checked oil level - good, just did an oil change with the timing set (5qts Quaker State 10w30 w/ Purolator filter - was going to run Seafoam so this was only temporary before going to Castrol GTX w/ AC Delco filter). Don't see any leaks. Haven't jacked the car up yet to check the oil pressure sending unit. Also didn't rev the engine to see if the light would go out. Figured I'd post here first to prevent any damage. No chatter since motor warmed up.
 


I bet that jelly gummed up in the oil pump, you should just put some oil in it then prime the system by cranking the engine with fuel disabled.
 
Didn't want to pull the front cover again so I pulled the plug wires and fuel relay. Turned the motor over for about a minute. Plugged everything back up. Cranked it up and let it run for about half an hour. No more oil pressure light! (Knock on wood.)
 


99% of the time when the dummy light comes on...your motor is toast. Consider yourself VERY lucky.
 
bluegtp91 said:
99% of the time when the dummy light comes on...your motor is toast. Consider yourself VERY lucky.
Click to expand...

I've always felt the light should say "replace engine soon" rather then "oil"

On another note, I thought somewhere along the line GM had the fuel pump wired so if the oil light was triggered it killed the fuel pump. Was this only an 80s thing? Or did I imagine the entire thing.
 
Nope...my oil light came on and the car was still driving. Definetly didn't cut power to the pump...that's for sure.
 
Some cars do have an oil pressure switch that kills the pump, these dont. I think it was like you stated an 80s thing.
 


I don't use the stock oil level sensor or oil pressure sensor. They come on at very low pressure when your already ****ed. Rarely do you see a problem with the car losing oil pressure with these motors unless they have been rebuilt or heavily modified. With the oil level sensor unplugged, the light comes on at times, but is never constantly on. Go figure.
 
IT'S BA~ACK...:mad:

(The Point)
Anybody know the ohm range for a functioning oil pressure sending unit? I assume this is something I can check like an injector or other sensor.

(The Rest of the Story)
So I started up the GTP and pulled her out of the garage to recharge the AC. Probably sat idling for about an hour. No oil light at start up. No oil light while recharging the AC. While disconnecting the manifold gauges and packing up, I noticed the low oil pressure light came on again--flickering at first then somewhat steady, but always fading in and out. I immediately killed the motor and went inside to do more research (YAY working on cars :th_bangheadonwall:.) Anyway after reading a few minutes I start the GTP back up and pull her into the garage yet again. No low pressure oil light during this. Jacked her up and put her on stilts. Disconnected the oil pressure sending unit and cleaned the bung and connector with non-chlorinated brake cleaner followed by dielectric grease. I plugged it back in, but haven't run the GTP since. I also removed the oil filter and drained the oil from it, replacing with new and inspected what I could with a mirror looking for any leftover petroleum jelly.
 


I agree with everyone else, A gauge is a must at this point.

You don't know whats triggering the light. I don't know about new ones but 1970s-80s GM's had the lights triggered right around 10PSI.
 
It souns like the pressure drops after it gets hot? I wouldn't think there would be any jelly left if you ran it for an hour. If it starts out good and drops when hot you may have a bearing issue. But I would def get a gauge and check it!
 
The Results Are In:

Start Up: 65 psi
Operating Temp (Idle 750 rpm): ~37.5 psi
Operating Temp (1850 rpm): 60 psi

I also tested the old sending unit vs new sending unit:
Old: 0.9 ohm
New: 0.5 ohm

So, I guess it's the sending unit after all. Let's hope this is the end of it. Thank you every one for the advice.
 
Scott Kane said:
The Results Are In:

Start Up: 65 psi
Operating Temp (Idle): ~37.5 psi
Operating Temp (1850 rpm): 60 psi

I also tested the old sending unit vs new sending unit:
Old: 0.9 ohm
New: 0.5 ohm

So, I guess it's the sending unit after all. Let's hope this is the end of it. Thank you every one for the advice.
Click to expand...

Don't you love when the outcome is like this?
 
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