what is oil pressure supposed to be at idle? I'm only reading 25-30 lbs just off idle ( 1200-1500 rpm). Seems to be way low to me. I'm scared to drive it

 

LOL!! No your good! At Idle a TPI only needs around 10psi to run..at high RPM if your getting over and around 45psi..your fine..don't worry. But if it makes you feel better..hook up a oil pressure guage and double check it.

 

Don't worry, if the pressure gets too low the fuel pump will shut off.

 

just wanted to be sure. my Lo3 was quite a bit higher. That's what I did, I went out and bought a cheap mechanical gauge to check it out. Thanx for the info.

 

Are you sure? I knoiw you can get a switch from Summit that does this but I didn't know our cars came with it. Anyone got any more info on this like where the switch is located?

 

I suppose it would depend on what year you are referring to but in my 89 shop manual there is no mention of fuel shut off except with the theft system. And if so I have never heard of it coming from factory.

 

i know there is a swich above the oil filter that activates the fuel pump when it sees oil pressure. Not sure about when it loses pressure though

 

I just changed my manifold with an aftermarket. While I had it off I decided to change my oil pressure switch, it went up 20-25# on the gauge. You switch might be getting a little worn out too. If you think something is worng with it, change the switch first, but it is a pain if you don't take off the manifold.

 

Our cars DO NOT have a fuel pump shut-off if the oil pressure drops. The ECM enables the fuel pump relay whenever it sees reference pulses from the ECM. The oil pressure switch by the filter is a fail safe in parallel with the relay that keeps voltage going in the event the relay failed. EVERY instance of somepone reporting their engine shut off with low oil pressure can be traced to a dead relay.

 

Interesting Ed... I had heard before about the oil switch that shut off the fuel pump, but didn't know if there was any truth to it or not. I do now haha thanks.

 

Yeah, i need to add it to the FAQ thread. It's one of the old myths that pops up from time to time that we have conclusively proven away here, thus the shouting in the answer for emphasis.

 

Are you positive about this ED? That switch on my car is for my oil pressure and a fuel pump shut off. I broke an oil pump shaft in my 305 pressure droped and the car shut off. Pulled the motor put in the new pump and the car started right up. I drove it for another two years befor I swaped it for my new motor.

 

If this is true then during an oil change if you dont put oil in the filter it will run for about 2 seconds without any pressure, since the filter has to fill with oil and the motor keeps running.....it doesnt start and then dies???

 

I'm 100% positive. Any correct wiring diagram for these cars will show exactly what i am saying, that the oil pressure switch is in parallel with the relay. If your car turned off when the oil pressure dropped then your fuel pump relay is/was bad.

for 90-92:
ftp://ftp.diy-efi.org/pub/gmecm/manu...730v8tpi-2.jpg

86-89
ftp://ftp.diy-efi.org/pub/gmecm/manu...165v8tpi-4.jpg

If factory wiring diagrams don't convince you, then feel free to unplug your oil pressure switch with the engine running and see what happens.

 

I will unplug the sensor sometime tonight. I let you know what happens-Jeff


My car shut right off. Now I don't know what this means but I would think I either have a wiring prob or that the oil press/fuel switch turned the car off.

ED- I wasn't saying you were wrong. Hope you did not take it that way. I just was telling you guys what happend to me-Jeff

 

Ok, regardless of the switch situation, am I ok to drive with 25-30# around 1000-2000 rpm engine speed? It creeps up to 35-40 with an increase in engine speed, but not nearly as high as most cars. My buddy has 45# at idle. :lala:

 

Yes you are fine with what you have. I run 30 lbs at idle and I just rebuilt my motor. It runs 60 going down the road. The reason you friend has such high pressure is because of a high pressure oil pump and/or the clearances and tolerances in the motor are smaller than yours. I would only be considered if my pressure dropped to less than 15 at idle.

 

Did you buy your car brand new from the dealership? What year is it? If its newer I could see it having that or if you arent the original owner someone could have installed the safety switch. Its good to hear though that you have some sort of protection in case that does occur.

 

I bought my 1991 Z28 in 1993 with 23000 miles on it. Now I'm worried that I have some sort of wiring prob

 

That I couldnt answer for you, but if it runs without any problems and the only time it will die is when you dont have oil pressure then I would consider it more than in working order its working in your favor if anything. I would enjoy knowing that if I lost pressure the motor would shut off, but I have a guage and keep an eye on it anyway.

 

I also have an AutoMeter oil press gauge.

 

I can vouch that it does not have that. I lost pressure in my 350 when I first installed it, and the car ran. (Oil pressure switch took a crap.)

 

like 15 peeps said your good to go!...at idle mine is about 30 and crusing its between 45 and 60

it would of been cool if gm actaully did that....like if your car rolled or something all the oil would go to the top of the motor..no oil pressure so that switch would turn off the fuel...(for safety reasons..like your car blowing up with u in it)...

but were talking am GM here lol always out for a quick buck

 

Um guys my oil pressure on my rebuilt motor is freaking <b> 10 PSI in gear at idle </b> its a high volume pump too.

when i first start it i see almost 80 PSI but when the oil warms up it just drops like a rock. s'tat bad?

yeah it comes up to 30-40 PSI while im driving. im just worried about the thing in gear at idle like at drive thru or in traffic 10 PSI is scary to me!!!

 

dude your fine. i just put in a race-350 in my iroc and my pressure barley registers at idle. when im cruising in 5th gear its like 15. so far seems to run great.

btw- i also have an aftermarket oil guage but its not hooked up because i dont feel like pulling my intake to get to my oil pressure. can i hook it up somewhere else?

maybe just drill and tap a hole in my filter?

 

damn i don't think there's much i can add to what rockfourone said. i'm just glad i saw it for myself and didn't get second hand info.

 

Ummm Yeah...

 

There's a scenario which accounts for low/zero oil pressure shutting off the fuel pump...the FP relay has failed. In this case, the only way the FP gets voltage is when the oil pressure switch closes.

 

Wow. Maybe it's time to start a FAQ-like list of incredibly stupid ideas posted here. This one being at or near the top.

 

While you're at it, you should grind a hole in your gas tank for a fuel level sensor too. Make sure that it throws a lot of sparks because the more sparks it throws, the cleaner the metal is. Gotta have clean metal to make a good ground for the new level sensor.

 

ok for those of you that have no sense of humor i was kidding about the hole in the filter. i mean come on do you really think after i built my entire engine from the block up i wouldnt know better than that?

take a joke guys....

 

roflmao...actually, yes it is VERY easy to believe you are that stupid. When you've been here as long as some of us, we have heard things that are unfathomably moronic. Even by people who claimed to build an engine or do other seemingly advanced tasks. Some of them even post semi-regularly.

 

The best I ever heard, was some kid bought a Turbo Eclipse that had a blown Turbo unit. The owner of the car told him he was just out of "Boost Juice" and needed to goto pep boys or autozone and pick some up.

Poor kid, the guys at DSM.com set him straight and helped him to change the turbo on it.

Car people, some of the best people on earth.

 

hahahahahaha!!!!!!

well if he was dumb enough to buy a r*cer then i guess he would belive that too...

 

Dumb enought to buy a r*cer? You mean a turbo awd DSM? Just because a car is imported doesn't mean it's a *****. Those cars with little modification can outrun a 3rdgen anyday. Try not to be so ignorant.

 

Nasty t/a,

im not saying that r*cers arent fast, its just that i dont really care for a lot of the people that drive them. granted, a well built 4 banger with 10,000$+ in it would make a normal thirdgen look stupid. but its not the reason that i and many other people on this board dont like them. now im not going to get into the domestic/import debate, so all you moderators out there please spare me, but i will say that many of the people that drive imports and pimp them out are usually rich urban kids with more money than sense. not to stereotype, but thats just what ive seen. i mean, look at an import show, then look at a muscle car show. at import shows, everyone is all about bragging and being snobbish and just generally being ******. at a classic/muscle show, people are freindly and in good spirits. they share tips and advice, and everyone is always ready to help if you have a problem. this is just what ive seen, dont think im being closed minded. its just that i like the idea of 8 pounding cylinders roaring through a throaty exhaust and tearing the asphalt off the ground, a lot better than a 4 banger with a rattle-box muffler and techno music waking the dead.

just my $.02

 

ok