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low oil pressure


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4 hours ago, Wally said:

after all comments, i am concerned about sump pump. I know i re-used old one so i am gonna eventually drop the pan and check all that out.



Sump pump?

I have no idea what this means. A house I lived in once had a sump pump in the basement.

Your L series engine has an oil pump. The pan doesn’t have to be removed to take the oil pump off, it bolts to the lower right front corner of the timing chain cover. Four bolts, drops right out.

You may have to take the front stabilizer bar loose to get room.

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18 hours ago, Wally said:

I think it might be called the "oil pickup". take the oil pan off and you will see it there. 


Again, unless the engine builder did poor work, or you have introduced something to the crankcase that doesn’t belong, there won’t be much to see, or do.

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There's a chance you have mismatched parts. The oil pickup could be wrong. The oil dipstick too which would show full when it could be low. 240, 280s and ZXs all are different.

The high pressure bypass under the oil filter could have a weak spring. Teflon tape on the oil sender threads could be blocking the hole into the sender. 

That's a few things I've read on here over the years. If the top of the head is soaked with oil I wouldn't worry to much. 


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here is an update. I got in the oil pressure gauge Steve recommended. i put it on and you can see results. The clear image is at idle, 16psi. When revved up psi goes down (blurry) to about 13 psi. 

Lot of comments recently to go through but for now here is the dipstick that came with car. Also where finger is is where oil shows. Anyway to know if this is proper dipstick? 

i will change the oil (i can get a sense of how much oil is in there too) btw how much oil should engine hold 4-5 quarts?

I will also check the pickup and take images... I have a new OEM oil pump i could put on and might

but i dont think thats the issue.


btw...not sure if it means anything.. but the engine sounds great. I have driven it on the highway and it runs like a top. had it up to 100mph and it had plenty of power left









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So Wally, this engine was running fine, and oil pressure was good, correct?

If so, then there is really only a few things it could be.

1. The oil pressure relief spring may have broken, or lost its springiness. This would result in low, or inconsistent oil pressure. The spring can be removed without removing the pump. 

An easy check.

2. The builder didn’t use thread locker on the oil pickup where it attaches to the bottom of the cylinder block, and the bolts have come loose. This would result in air getting sucked in and the oil would get bubbles in it. You would see this on the dipstick and in the oil you splashed everywhere when running the engine with the cam cover removed.

I doubt this is the problem.

3. the bearing clearances have somehow become too large. Excessive bearing clearances will definitely result in low oil pressure, but there will also be an accompanying knock as the rods and main bearings rattle about. 

Again, I don’t think this is the issue, as an engine doesn’t last long when this occurs.

4. If you reused the old oil pump, and it wasn’t disassembled, cleaned, and inspected to verify adequate clearances, it could be the cause of low oil pressure.

5. The correct amount of oil in the crankcase, and the correct dipstick.

The oil sump capacity is 5 quarts if I remember correctly.

Starting with an empty crankcase, and a new filter (should hold about one quart), refill the engine with the correct amount of oil, start it up, run for a minute, then shut it off.

After waiting five or ten minutes, check the oil level.

It should be within the high and low marks on the dipstick.

(as for the question of the correct dipstick, have you replaced it with the one that was with the engine originally?)







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2 minutes ago, Racer X said:


(as for the question of the correct dipstick, have you replaced it with the one that was with the engine originally?)

The oil stick that came with the car when i got it is the same one i am using now. I did a google search and looked at the ones selling on ZCD. It appears mine is the same or similar to those. So to me it seems proper one. 

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reading comments. is the  oil pressure relief spring  and the  high pressure bypass  same thing?

would i be correct in assuming i need to remove oil filter to find this?


If you dont mind, can a couple share oil they use? I have Castrol 10w30




Edited by Wally
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Might help to have an illustration of the oil path to ponder.  Pressure is caused by resistance to flow.  Flow starts at the oil pump.  You said that you installed a new oil pump, but who knows about its quality.  The oil pump has a relief valve that could reduce pressure.  The oil filter area has a relief valve but flow will still be resisted by the main bearings and the restrictor at the supply to the head.  So that bypass doesn't really matter.  Hard to know how much oil could pass through that restrictor to the spray bar.  I think that I saw it in one of your pictures.

And, apparently, some engines have another supply passage to the head at the front.  It's not shown in the illustration but I have a vague memory of reading about it.

A thought that just occured - the fact that pressure reduces at higher RPM might be caused by cavitation.  Which could be caused by a restriction in the supply to the pump.  So, it kind of circles back around to the pickup tube.  Maybe you got a gasket on backward or something.  The pump just moves volume.  Pressure is caused by restriction.


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