Opinions please: 4G63T low oil pressure

I now have a 90 Eclipse (6 bolt) 4G63T (supposedly about 180,000km according to the donor car odometer) running in my 93 Summit coupe. Oil pressure is
very low, such that the idiot light flickers all the time. The std Eclipse gauge swings to mid range on start, then quickly drops to near zero. There's no tappet or big end bearing noise, and the engine runs smoothly. I'd guess there's about 20 psi. There's certainly enough pressure getting oil to the turbo, as the supply tube fitting on the head had a wrong size crush washer that spat a lot of oil on first start.
I can feather the gas pedal till the idiot light goes out, then a blip on the gas turns it on again. The corrrectly tightened alternator belt SEEMS to squeal (more) occasionally when I depress the clutch. The oil pump is correctly aligned with the cams.
I've checked the oil pressure relief valve and oil cooller bypass valve: both look normal.
I know that oil pumps wear out, and worn bearings can cause significant loss of pressure. Other worn engines I've fixed usually had about 1/2 normal pressure with worn bearings, and one (a Renault) had an internal pump gasket failure that leaked pressure back to the sump, thus giving 15-20psi. Blipping or revving would cause pressure to increase at least a bit.
The 220,000km n/a 4G63 I just took out had decent oil pressure all the time, despite the thrashing I gave it for the last two years.
Some ideas: I see in my manual that the oil pick up tube has a replacable gasket. It appears to be on the pickup, not pressure, side. If this fails or leaks, could this be the cause of low oil pressure? It may be causing the pump to suck air (and less oil) once the engine starts and the level drops down.
Possible thrust bearing wear, though there does not appear to be any fore-aft crank movement. Crankwalk is not usually a problem in the 6 bolt engine, but could be the problem is evidenced by the alternator belt squeal. The "blip the gas and idiot light comes on" is a worry. Could be worn big-end bearing(s).
What I find odd is NO increase in oil pressure on revving the engine. Its as though the pressure is leaking away somewhere (or not getting generated) before it gets to the bearings. I'd expect even worn oil pump would allow SOME increase in pressure. Is this reasonable for the 4G63?
What's the most likley problem here? Oil pump, bearings or both? Or something else?
I'll get the sump off next week and have look at the pick up gasket and check the mains, thrusts and big ends..
Stewart DIBBS www.vysor.com/lancerproject
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Another question on oil pumps. If its NOT correctly aligned with the cam belts, engine harshness results. I'm not hearing this, but does this misalignment also cause poor oil pressure?
Stewart DIBBS www.vysor.com/lancerproject
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Well, I have a bit of egg on my face. I borrowed a mechanical gauge from a pal at the local garage, and the guy suggests that maybe the wires to the pressure switch and pressure sender are swapped. "No, no, they are correct" says I ... so I looked, and sure enough they were not bloody correct. Swapped them around, and voila, oil pressure. Fastest bearing job I ever did.
So... if you have a flickering oil light, and the gauge is reading full on at start, the dropping to zero, check the wires to the switch and sender.
Now all I have to do is fix the %@&^#* clutch.
Stewart DIBBS www.vysor.com/lancerproject
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Hi Stewart:
Than goodness for clever mates!
Regards
John
wrote:

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I assume you have checked the pressure with a real gage down at the filter? The light should only flicker with 15 of less pounds per square inch. If it is truly low, you may want to pull the oil pan and check the bearings and oil pump pickup. Crap clogging the mesh at the pickup or worn bearings will cause low pressure. Other than that, you'd have to assume the oil pump (rare IMHO although something could have clogged the bypass open).
If the idiot light is wrong, suspect something in the sender bell housing. Take it off and blast it with some brake cleaner.
--
Todd Honea



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could be a squirter stuck open ..... on a 2G this is the theorized cultprit in crank walk. this page discusses the squirters and that theory. http://www.magnusmotorsports.com/crankwalktheory.htm remember, the n/a cars have no squirter. nothing to fail. i have seen a lot of posts that mentioned flickering oil lilghts in DSM groups. the hellical gear oil pump seemed to supply more pressure on my 1G car.the front case/pump assy is on ebay every week for $187 U.S. dig the fuel pump: http://cgi.ebay.com/ebaymotors/ws/eBayISAPI.dll?ViewItem&rd=1&itemy22043730&category3555 you can also buy higher flow pump for the application from any dsm vendor but this pump is good for 15 psi of boost with no problems. perhaps you have a boost leak causing the bucking and loss of power. you should be able to pull hard to 7000. peak hp was 195 for that motor at 6,000 rpm, so falling off at 4,800 is bad....the rev limiter is at 7,500.

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another possible cause, check the clearance on the pick-up tube for the Oil pump. if it's too close to the pan, will not pick up. A common prob on peeps that build their own motors & some backyard billy joe bob's mechanics. We've had a couple come to our shop to fix same prob. Not that this is a fix for all of them, just a common one.
UrHookUp
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