My oil pressure gauge fluctuates quite a bit when it shouldn't (cruising/turning/stopping). Sometimes the analog drops to 0 for 1-2 seconds and the red "Check Gauges" light comes on. Then it goes back up. Other times it will drop very low momentarily, but not all the way to 0.

It just started doing this a couple weeks ago after I had my front control arms replaced and other suspension work done on my car.

Do any of you know if oil pumps usually go bad? 113Kish miles on my '95 Auto daily driver.

I'm going to have the sensor/sender replaced... hopefully that will fix it.

 

If your oil pressure is dropping off to zero, its time to stop running your engine. It needs to be diagnosed ASAP.

If it is the oil pressure sensor you are in luck.

Mechanical parts are not eternal, some last longer than others.

This thread will generate a lot of posts.

 

How is the oil level?

First, I'd put a mechanical guage on it. Also, maybe the connection was knocked off a bit when the work was done, although it isnt really in the same vicinity as the worked performed.

My guage fluctuates a lot but it has never hit zero with any idiot lights coming on. It is either around 40 at a hot idle or 60-70 when above 1500 rpms. 1991 guages are iffy at best.

Mike

 

I'm guessing your issue is not the oil pump. They don't fail "intermittently".

 

Check your sending unit probably taking a dump.
My DD same thing, started fluttering at idle and slowly losing pressure wouldnt build press. like it did. Oil pumps either work or they dont. Rare to "go bad"

 

I was doing a google search on "LT1 oil pump", and I saw these:

http://www.pro-jectioneng.com/ops.html

http://www.herronperformance.com/sto...&productId=317

Has anyone heard of these before?

 

You should consider diagnosing your problem before you start throwing parts at it.

 

I just replaced my oil sender a few weeks ago, it started fluctuating while cruising .. I hooked up a manual gauge to check it out , then replaced the sender with a AC Delco , problem solved.Can't believe the original only lasted 23 years, what junk.......WW

 

An oil pump is nothing more than two gears and a spring loaded valve. Not much there to fail. Wear, yes but that happens very slowly.

 

Oil pumps are mechanical devices. Once damaged or worn-out they are worn out...no self help with pumps.
As they wear so does the display or the pumps output. It would show as a consistant line that slowly dropped to the point where it is today...unless there was a catastrophic failure that caused instant failure of some sort..broken shaft, or pick up tube fell off...where it would be dead and stay dead. Oil pumps get the best lube, are low stress and simple in design. They are VERY reliable and have great longivity but they can wear out...generally after everything else does.Long after...113K is brand new.

Your problem in all likelyhood is electrical. The signal from the OP sender is measured in resistance...and resistance can come from dirty connections, loose contacts, a change in conditions in which the signal operates and travels....almost ANYTHING can effect resistance and a change in resistance IS a change in oil pressure....

First thing...find the wires to the sender and pull them off and clean and replace. Observe the difference in the display. If it changes or stabilizes you have solved the most common of ALL C4 problems..electrical system integrity.
If after the cleaning the gauge stays the same then look for the grounds for the harness on the block near the oil filter. Check ALL other harness grounds that you can find. Worst case would be getting a new sender. Be sure to buy the name brand...the cheapo chinese copies seem to come with faulty readings. You can install a mechanical gauge to sooth your nerves if you like but thats not the permanent fix...just to diagnose.
Service work OFTEN means a gorilla like approach to yanking harness sections out of the way because a tech is too lazy to d/c things and do it as if he were changing his own kids diaper. Its amazing how sensitive the harness can be to being tugged and pulled around...old wires are brittle and break, connections get loose, systems start to fail due to poor signal integrity.
Your FSM will show you where all the ground points are and where all the sensors and other related componants live.
So, there is a LOT to do before you spend a dime and chances are that you will solve the problem before ever having to reach in your pocket.

 

I had similar symptoms with a stuck bypass ball/spring on an old Pontiac I rescued years ago. However, I agree with others that its likely an electrical issue with the sending unit or gauge.

 

Niether do rod or main bearings. I'm guessing the problem is low oil level or a faulty oil pressure sending unit.

 

And the gears are always spinning in oil. Very little wear that way. I have a sender from the aftermarket and sometimes it sticks. May stick on 11, may stick on 48. Usually if I shut the car down and restart it, things go back to normal.

 

an issue with the sending unit/ gauge.

Drive on!

 

You may have lost the pick-up tube on the oil pump. I have a '95 Z28 with that problem.
Its ok on flat roads and modest driving, but oil pressure goes away on hard braking. Does
your car do that?

 

I've read each and every one of the responses, haven't had time to look at the car more. Will be replacing the sender unit later this week.

Interesting, I see that leesvett mentioned it too. Yeah I've noticed that the pressure usually is drops when my foot isn't on the gas pedal (as it should be). Additionally, the lowest points seem to be when I'm braking/turning.

 

Thats normal.

 

With the LT1 - there is a pressure switch on the top rear of the block. With no / extremely low oil pressure - it turns to power to the fuel pump off. So - if the car actually had no oil pressure it would probably stall out in seconds.

SO - the liklihood is that the problem is with the gage BUT since very very little time with extremely low or no oil pressure will do very expensive damage - this is not a place to hope everything is OK. Either change out the pressure sensor and see if that solves the problem or hook up a mechanical oil pressure gauge to the engine and verify that you do have good oil pressure even when the gage says you don't.

Previous posts are correct - if the oil pump is "worn" out - it won't get better and worse, but if the oil pickup has seperated from the pump inlet - you would get good oil pressure at times (when the oil level was above the pump inlet port), and virtually no oil pressure when the port was uncovered. Pressure would be related to the level of oil in the pan, and how fast it was draining back from the upper part of the engine.

GOOD LUCK

 

Eh, look at that again... The ops does (on older) have voltage that's sent through and to the fp relay, but this only happens after you build about 8psi. There are 2 "turn on" signals for the fp relay. If for some reason you lose the one from the ECM/ignition, it will be triggered by the ops.
BUT even if you unplug your oil pressure sender, you will not lose your fuel pump. Guaranteed. That's a backup for starting, and in no way was meant to shut off the pump in the event you lose oil pressure.
GM did this on a lot of cars. It's well documented.