Oil pressure help!

I have a 1991 Caprice wagon with the mighty 305 TBI, all original. Couple of days ago I noticed that when first crank car the oil light stayed on for say 30 seconds or so, which is longer than it had been staying on. Yesterday it stayed on for a little longer say a minute. Today it stayed on for about 5 miles. When rpms went down it would flicker then go off, when accelerating it would come back on. After about 5 miles went off and stayed off for rest of way to work. No unusual noise, I do have oil, no skipping, runs as good as always. Thinking a bad sending unit? Needing opinions. Thanks!!

Before you panic change the oil and filter. If that does not help, change the sending unit, they're cheap.

305's run FOREVER...

Probably a dirty oil pump pickup screen, that is if you're done regular oil and filters changes.
Doesnt sound serious! Famous last words which will no doubt come back and bite my ass!

You should also hook up a test gauge, mine was showing really low, then I hooked up my test gauge and it was at 40psi at start and dropped down to 30 when reaching temp.

^^^^Put a mechanical gauge on it. They are cheap, and you will know exactly what you have. I put a mechanical gauge on mine, and had no pressure at idle, and 5 psi at 3000rpm. I swapped to a low mileage 350.

It could be the relief valve in the pump. It is spring loaded, and the spring could fail. I had one stick closed, and it pushed the gasket out from under the oil filter. Gauge went full high, then the oil shot all the way across the street.

I have a good 305 from my 91 OCC for cheap if you are interested. I believe it needs a rear main seal, and maybe a seal for the oil cooler adapter. It has good oil pressure, and ran good prior to removal.

Guys, thanks for the help. Saturday I changed the oil and filter, and bought a new sending unit. Took old filter off and after draining it it weighed like 2 - 3 pounds. I think the culprit was a clogged filter. Didn't have a 1" deep well socket to change sending unit with. It is 12-15 miles from my house to anywhere to buy anything, so decided to change oil and see what happened. Light went off just like supposed to and running like a top since!! Thank ya'll again for the help.

That's one heavy filter Glad the problem is solved.
Pete

chevy5seven wrote:

Guys, thanks for the help. Saturday I changed the oil and filter, and bought a new sending unit. Took old filter off and after draining it it weighed like 2 - 3 pounds. I think the culprit was a clogged filter. Didn't have a 1" deep well socket to change sending unit with. It is 12-15 miles from my house to anywhere to buy anything, so decided to change oil and see what happened. Light went off just like supposed to and running like a top since!! Thank ya'll again for the help.

I have changed the oil pressure sender with a crescent wrench. It is tight, but it will work. Having read the rest of the post, it does not seem like you need to change it anyway, so it is a moot issue.