oil light at 55psi

[prowney]

I just purchased a 76 spider locally and have really enjoyed reading the plethora of info this forum has put together. Unfortunately, I have an issue that I haven't seen addressed yet. My car has an oil gauge in the dash that seems to function normally. It reads between 45 and 65psi (depending on rpm) when cold, and 0 in idle to 55psi at 3k rpm when hot. That didn't sound too bad from what I've read on other postings, but after about 10 minutes of driving, even though the pressure stays at a steady 55psi, the little red oil light comes on. I was wondering if anyone had seen something similar to this? I would think if the oil pump has issues, that the light would be on when the engine is cold as well. Thanks for any help in advance.

Paul

[kilrwail]

Does the oil light come one when you first turn the key, before starting the engine? The electrical gauge is notoriously unreliable. I suggest you spend $30 for a mechanical oil pressure gauge to see what you've really got. You can install it in either sender port (light or gauge), with the correct adapter. NAPA has them. Zero oil pressure doesn't necessarily relate to an oil pump issue - it could be bearings! You need to find out what the real pressure is ASAP.

Then take a minute and go to the Introductions page and tell us more - with pictures if possible. Welcome to the forum.

[mbouse]

i'd suggest that the oil pressure GAUGE sending unit and the oil pressure LIGHT sending unit are two different sensors, and that either one or both of them could be bad.

when i added an oil pressure gauge, i tried three different sending units before i got one to make the gauge work.. the entire time i was experiementing, i relied on the light & its sender.

i suggest trying a different/new oil pressure light sender.

[kilrwail]

The mechanical pressure gauge would fit either sender PORT, and does not rely on a sender. The light only tells you when pressure goes to zero and by then it's too late. Fix the light if you want to, but get a reliable gauge to be sure.

[prowney]

The light does come on when I first turn the key before engine start. It also comes on as the oil starts to warm up and the idle pressure drops below 5 psi. Finally, as stated above, if driven long enough it will come on regardless of pressure and stay on. I'll look into a mechanical gauge and replacing the sending unit and see what happens. Thanks!

[So Cal Mark]

sounds like the warning light is working properly, and adding a mechanical gauge will start the process of repairing the motor before it fails

[prowney]

I installed a mechanical oil gauge. The adapter it came with is aparently close because it fits, but not an exact match because it leaks where I attached it in place of the electric pressure sender. Results were 40-85psi when cold, and 15-55psi when warm. Thoughts?

[pope]

One quick thing to look at is to see if the oil pan is dented on the bottom where the oil pickup is located. It could be starving the entire system.

[kmead]

I installed a mechanical oil gauge. The adapter it came with is aparently close because it fits, but not an exact match because it leaks where I attached it in place of the electric pressure sender. Results were 40-85psi when cold, and 15-55psi when warm. Thoughts?

Normal

[mdrburchette]

If you're certain of the wiring for the idiot light, I'd be concerned about that light coming on. Did the car sit for a long time before you bought it? I bought a little Toyota Celica that showed great oil pressure but the oil light came on and the engine locked up because of sludge in the oiling system.

[prowney]

Looks like it was the sending unit for the light. After replacing that, everything works as advertised. I really appreciate the advise to install a mechanical oil pressure gauge. It works so much better than the stock electric one. Thanks for the help!