No oil pressure on start up???

[BLstangin]

Ok guys i had an oil pressure issue a while ago and finally got it fixed by puttin on a new pump and bearings. When i first start it in the mornin it takes like 15-20 seconds to shut the light off, confirmed it's not getting oil pressure right away buy puttin a gauge in. After first start in the mornin doin that it gets oil pressure like when i go to lunch it only takes bout 5 seconds. If i shut it off come back in 10 minutes it goes out right away like it should. I think it's draining it's oil back, but where???? I have a wix 51394 filter on it that's supposed to have the anti drainback valve in it. This never used to be this way until i lost oil pressure back when. Do you guys think that filter bypass inside that tube that holds the filter on could be leaking and letting the oil drainback???? Any other ideas. It can't be good for it.

[marc780]

My guess is the low oil pressure has nothing to do with the drainback valve or the oil filter. If you are getting at least 40 psi of oil pressure at highway speed when the engine is hot, the engine is probably ok for a while.
Since its winter in Minnesota that means your oil is thick in the morning. I think id try either a synthetic oil or i'd go down a grade - that is maybe i'd try 5w-20 oil.

[BLstangin]

Ok i only got about 28-30 goin down the highway at 2,700 rpm so oil pressure isn't great. It's got 10 at idle, and 50 at 6,000 rpm. So it works, just not great. Only problem is in the morning. I'm not worried bout the acutal pressure, it's just that it looses its prime. This only started after i had oil pressure issues. Before that i never had a problem with the thing. It would always build pressure almost instantly. That's the thing, even cold it would shut the light off right away. Now it has to run for way to long to build pressure. Since i'm not real familiar with the oiling system on these things i was hopin someone else would know????? I'm runnin 5w-30 right now and afraid to go down cause of the lower pressure hot. Thanks for your guys help.

[GaryS]

If you have verified that you don't have oil pressure for 15-20 seconds after start up, then you might have a serious problem. All of my cars put out the oil pressure light within 1-2 seconds.

I have read that the majority of the wear on an engine is starting since it is running with only the oil that clings to the metal surfaces until the oil pump can do its thing. If you are sure that your oil pressure gauge is accurate, I would take this car back to where ever you had your new oil pump installed and have them check out the pump and its tolerances.

Gary

[marc780]

Blstangin the rule of thumb is 10 psi of oil pressure per 1,000 rpm. And this engine is too low. So i'd be asking myself just how much longer i'd expect this engine to last, and what i'm going to do if and when it blows.

[BLstangin]

Ya i know the oil pressure is low, but i'm more worried bout not havin oil pressure almost instantly. I don't know the oiling system on these to well as i've never had one apart, and that's why i don't know what to do. I put the oil pump and bearings in myself. I rebuild engines all the time, but this is the first time i've ever delt with a toyota and therefore i dont' know what makes it tick sorta speak. It seems to me like the reason i've got low oil pressure is cause there is still a problem or something somewhere but i'm unsure. It doesn't burn any oil or use any antifreeze. I just need to figure out why it's draining the oil back. If it blows up i'll either rebuild it or slap a junkyard one in there. I'm just tryin to learn how this oiling system works, because if i can figure that out i can fix it. does anyone know of any places where these things are prone to oiling issues??? i'm almost wondering if the block or head cracked or something to an oil passage, or if the head gasket coulda blown in the feed line to the head and is dumping the oil somewhere else??? is this possible??? i've never had the head off of one of these or anything so i dont' really know how it works??? Anyone????

[Nad1370]

By any chance, did you clean out the pick-up screen when you replaced the oil pump?
A restricted pick-up screen would def. give you a low reading.
Also a broken up pick-up screen gasket ( air escaping through while oil pump is pumping ).

[Eye8Pussies]

or even possibly a pressure valve is stuck open instead of opening and closing to help regulate the oil pressure

[BLstangin]

I completely cleaned the pickup screen and used new gaskets. The pickup screen didn't look dirty at all when i took it out. Actually the whole motor looked really clean inside. And the only pressure valve that i know of is the relief valve on the oil pump and since at higher rpm it builds 50 psi i'm thinkin that's o.k. especially since its new, it comes with the oil pump. Thats why i'm kinda baffled as to what's goin on.

[Nad1370]

Well since you already covered everything that is possible and you build engines.
I would go with too much bearing clearance causing low oil pressure during cold start-up's.
It's possible since you had the oil pump problem.
Maybe it just wore out the bearings even more but not to the point it would start knocking.

How many miles on the motor?
I'd suggest switching to full synthetic(5-30) for added protection during start-up's.
Maybe even using oem oil filter and replace the oil sending unit as well.

[BLstangin]

thanks for the tips. I put in some lucas as it has shown in our circle track race motors to make them live a lot longer and i changed out the sending unit. I know it has a problem cause i verifyed it with a snap on oil pressure gauge taped in at the sending hole. And i replaced the rod and main bearings and they plastiguaged at .002. I know that platiguage isn't perfect cause i have found it off by .001 when using my dial bore gauges and mics on my race motors but it shows me that it should be close enough. Also the crank was not scored so that should be o.k. But it could be the cam bearings but i took a couple caps off and they came out o.k. to and weren't scored. That's why i'm kind of at a lose as what to do without tearing it down. Which i can't do right now cause it's my only vehicle right now. Thanks though for all your guys suggestions.

[Eye8Pussies]

at this point, I'd say it'd be worth it to take to a dealership just for diagnosis, and then fix the problem yourself (if they can figure it out)