Hey Guys...

Hoping one or two of you might have encountered this rather strange oiling dilemna...

On cold start up, the engine shows zero oil pressure (both guage and DIC) and usually stays at zero for a couple of minutes. (Yes, I already replaced the oil pressure sending switch behind the intake). Whats strange is that the engine isn't any "louder", the valvetrain isn't clacking away which you would expect, and usually when I pull out of my driveway after warming it up for a minute or two, the guage slowly creeps up and shortly thereafter will read normal while I am driving it around. Once the car is hot, if I go back and re-start it, the oil pressure seems "normal" and I don't seem to have any issues.

I replaced the sending unit last night which I was hoping would cure my problem but the guage is acting exactly the same. Sitting there with the car runnning displaying zero oil pressure for a few minutes is anything but confidence inspiring....I'm wondering if I spun a main bearing which isnt allowing oil pressure to reach the sending switch area, but yet I'm still getting pressurized oil to the lifter galley therefore no valvetrain noise when the guage is reading zero.

Any thoughts or suggestions???

Thanks,
Tony M.

PS Might try cutting the oil filter open this weekend to look for some bearing debris....obviously hoping that's not the case, but I can honestly say that this engine doesn't owe me a dime...

 

Could it be a bad o-ring on the oil pump?
Phil

 

Thought about that but if in fact that is true, I do legitamately have zero oil pressure for awhile in which case I would expect the lifters to bleed down and start clacking like crazy.

Very weird...

 

Tony;

You should trust that you really dont have oil pressure, that its not a gauge or sending unit messing with you. The way it is acting is a lot like a case I had on a customer's car not too long ago: a small piece of debris was caught up in the oil pump, effectively shimming the main oil pump rotor from the sidewall, allowing it to lose its prime. It was the damndest thing I've ever seen. By the time I found this problem, I had done everything from drop the pan and check the bearings to blow out all oil galley's, new sender, etc. The debris was a collateral effect of piston damage he sustained a month prior from a failed valve spring allowing the valve to punch a hole in the top of his piston. A small piece of debris the size of a pencil lead tip worked itself loose from a nook or cranny of the motor a month later and sideloaded in the oil pump. He had the exact same symptoms as you- with no valve train clatter or any other sign of not having oil to his valvetrain. Just a suggestion from my own experience.


robert / gen 3 ms

 

Thats not what I wanted to hear....LOL

There has to be SOME oil moving thru the motor or how could the lifters not collapse and make a racket?

I definately appreciate your input...I might have to pull the shortblock when I do the 225 install....looks like I might be needing a freshen up!

 

Could try starting/cranking it with the valve cover off just to watch for oil feeding from the pushrods - just realized that's not a simple thing with the coil packs there (starting anyway)

 

Tony, only way to be sure is to remove the sensor and install mechanical oil pressure gage. There are 2 places to check.....oil pressure sensor and plug on the drivers side just above the oil pan (GM use this for priming).

 

Thanks for all the input guys...

I'm going to cut open my oil filter tonight and check it for signs of any bearing material or other "unwanted" debris.

I think I might have an "oil priming" issue as Rob had suggested....I was just hoping there might be an easier solution.

Looks like I might be laying up the car a liitle sooner than I thought for the 225 install.

Thanks,
Tony

 

You also might have your oil analyzed to make sure you know if any damage has been done. I had oil pump failure at 10,000 miles that trashed the crank and bearings. I had the oil analyzed prior to taking it to GM and found abnormal amounts of Aluminum, Copper and Tin. I knew I had bearing damage before I took it in.

 

Well....I cut the filter open tonight and the "pleats" of the filter looked very clean....there was some metallic debris at the bottom of the filter housing which obviously couldn'y get thru the filtering material, but I really didnt see any gold or copper colored fine debris which would have indicated I might be getting into some bearings a little. I think considering I certainly do not baby the engine (shift light goes on @ 7K), a little bit of fine metal debris seems fairly normal.

I did a leak down and the worst hole was slightly more than 2%....outstanding all things considered (50K on the stock GM shortblock). The other thing I did was fabricate a billet adapter to replace the GM oil temp switch on top of the filter pad....I tapped it for eigth inch pipe thread and ran a line to a mechanical pressure guage. At this point I'm hoping there is something funny in the computer which processes the information from the sending switch but I'm not holding my breath. I have a feeling its a "priming" issue and I will probably have to get to the pump to address that.

Final chapter on Saturday....have to re-adjust my rockers and get the car back together to fire it up and see what the mechanical guage reads.

Maybe it fixed itself when I changed the oil and filter tonight.....

Fill all of you in over the weekend sometime.

Tony M.

 

Well I'm glad to hear you didn't find chunks in your oil filter.

It sounds like you have a pretty good idea what it is and I'm willing to bet an oil pump is in your future, just consider thats alot easier on the wallet than a spun bearing

 

Could it be defective heads


OK before I get pounded, that was a joke. get it ha ha

I think its the oil pump going. Ill throw in a guess like everyone else

The right guess gets a new set of AFR 225's

 

Damn Phil....I was thinking the same thing....the velocity is so high it sucks the oil right out of the pan!!

 

Im glad you understood it was a joke. I was affraid a nut on here was going to bash me.

I did enjoy your responce

Did you figure out the problem yet?

 

The mystery continues...

After finishing up the leak-down test and running the line for a mechanical guage, I let the oil drain all night with the car on an incline so to get every drop of old oil out of the pan. I then proceeded to re-adjust all my rocker arms (Crane 1.7), install new oil and filter, and basically just put her back together so I could fire it up and check the mechanical guage reading against the factory instruments.

Turned the key and it fired to life fairly quickly with a bunch of clatter from the valvetrain (briefly) as the oil pressure had to fill all the oil gallies, new filter (which I always pre-fill), and pressurize etc...normal stuff when draining the oil completely and changing the filter. A second later or so the clattering of the valvetrain quieted right down and the mechanical oil pressure guage as well as the one in my car are quickly swinging up to 40 PSI....just like normal.

I let the car sit for a few hours so it was good and cold again, tryed re-starting it and everything seemed normal again (no clatter from the valvetrain this time as the lifters were already filled with oil). Took her out for a nice drive and parked it back in the garage last night.

So know I'm left with two thoughts....

1) What did I do that "cured" the problem (assuming nothing changes)?

2) The lifters briefly clattering till the oil got thru the engine tells me that if I really had ZERO oil pressure previously, it would make sense that the valve spring pressure would have bleed them down and they would have been making a racket if in fact it was idling with no oil pressure.

Very weird....but I'm glad things "seem" to be back to normal. I'll follow up in a week or two and let you know how things go.

Thanks to everyone who took the time to write and make suggestions...

Tony M.

 

That was the fix I almost suggested. Ok Ill settle for a new set of 205s and we'll call it even. Send them to East Coast Supercharger. My car will be there tomorrow for a cam installation.

I still think something was clogging the line or pump

Im glad it is nothing major. We alway think worst first.

 

Tony I have seen this all too often- What pump is on the car? Stock OEM, or a new unit when you did the Heads/cam?

The pressure relief will get stuck open thus causing the low oil pressure. There is some pressure, 5 or7#s, enough to float the crank, but just enough to make the PCM go haywire.


Tell me what year that pump is off of, and I will let you know if you should worry

Louis

 

Hey Louis...

How's it going?

The pump is the stock pump that's been in the motor for 50K. My car is a 2000 model, but it was literally built the last week before the plant commenced building the 01's, so it could be either. When I do the 225's soon I will probably switch it out just to be safe.

Thanks,
Tony

 

We just had a customer with a 2000 and started it up, the guage read zero, he shut it down and brought it in. We replaced the pump and all is well.

I would swap it when you do the 225s

Louis

 

hmmm.. ..the other day my stock '98 (50K miles) did the exact same thing....both the gage and the DIC said zero pressure.. ..scared me to death. So I shut it off and immediately checked my oil and everything seemed fine...started it up and listened for the valvetrain rattle and none and so got back into the car and by then the oil pressure gage started to come up finally. It happened just that one time and never done it since, so I've been curious what it could have been.
John