No oil pressure... Except with cordless drill?

7

73 Black and Tan

New Forum User
I could use a bit of help here... (73 240Z running L28 block).

I'm in the middle of a project and I'm having oil pressure issues that I haven't been able to diagnose.
Before my current project I would often get low oil pressure once it was warmed up and when at idle. Wasn't sure if it was the pump, the sensor, the engine, or something else. So I went to see if I could 'fix' this problem while doing some other work..
This current project has me doing the following: removing the timing cover to fix a leak, new oil pan (baffled Arizona Zcar), new hoses, new belts, new water pump, new oil pump internals (went to add a high flow version but turns out it was the same as I already had, thanks prior owner, installed the new stuff anyway), new oil pressure sensor, new oil filter, oil change with added oil for the new larger pan, and a coolant flush.

Issue: finished all of the above and whet for a drive. The oil pressure was higher than normal, not off the chart, but higher than before, near the end of the drive pressure was showing zero when at speed. I pulled over and did a visual and audible inspection. Nothing seen or heard.. limped it back home for further evaluation.
I got a mechanic oil pressure gauge, took out the oil pump shaft and reinstalled the pump to spin it with my cordless drill, it showed oil pressure!
But when I put it all back together, and pull the spark plugs and crank it still shows zero?!
I took a video of the shaft with the distributor off while I was cranking it to see if the shaft was actually engaged and spinning, it's spinning just fine.

Any ideas what's going on?

My fear is that my drill is spinning faster than the car rotates while cranking and that speed is needed to make pressure (probably not a good root cause to this).

Before I admit that the summer driving season is over and I pull the engine for internal issues, is there anything else I should/could look into?

Thanks in advance for any help.
-Will
 
I don't think I understand your test setup - how are you spinning the oil pump with your drill and seeing oil pressure?

Anyway, cranking rpm is about 200 to 250, and I *think* drills are more like 600 rpm.
I think it's pretty normal to not see any pressure cranking, but not good to see zero pressure at speed.

can you drive it with the mechanical pressure gauge? do you see any pressure while driving on that?
 
Thanks @jonbills, I should have been more clear on the test setup.. I uninstalled the pump and removed the shaft that turns the pump, reinstalled the pump. Then took a very long flathead screwdriver cut the handle off, and installed it in a cordless drill. I then removed the distributor and inserted the flathead down through that distributor hole to engage the pump. I spun the oil pump with this drill set up (counter clockwise), and it did create adequate pressure.

I'd love to set up the mechanical pump to see what's going on while driving but it's not in a place conducive to that, and I'd be nervous with the below update:

Update: I removed the oil filter and cracked the engine over for about 15 seconds. To my surprise nothing came out.

This is making me think that maybe it's either
(1) I damaged the oil pickup tube when I installed the new pan and it is now too restrictive to allow enough oil to reach the pump under normal cranking speeds. Or
(2) when I reinstalled the oil pump shaft is is somehow not engaging the pump.. I can see it spinning the distributor but cannot actually verify the pump's actions.

I think my next step is to try to duplicate the results with the drill again.

Thoughts?
 
Is the battery in good shape? You can crank for a long time before the oil comes up even when everything is good.
I think if the distributor is spinning, the oil pump will be too.
You could maybe try the old oil pump and sensor to see if they make a difference.
When you said you installed new oil pump internals, what did you mean? I've only ever seen whole oil pumps for sale.
 
@jonbills , battery should be good, it's a Zero Gravity Lithium type on a trickle charger. But when you say "a long time" before the oil comes up what do you mean? I'd expect that it would suck oil from the sump and be pushing oil out of the filter housing within a couple of seconds, I've been cranking it for 10-15 sec without any flow. Am I missing something here?

And FWIW the longer story on the larger rotors is that I didn't know what the prior owner had installed when I ordered a new high flow pump. When I went to install the new pump I realized that it was the same rotor as what I was already running. I went ahead and installed the new pump anyway but during the shake down drive the pressure was a little high for my liking. It was during this same shake down drive when the pressure dropped to zero and led me down this path. I am thinking the higher running pressure and the now zero pressure were possibly two different causes. So rather than shimmying the new pump's spring to try and get the running pressure where I want it I decided to run the old housing with the old pressure spring, but incase there were any issues with the existing rotor that I couldn't see (warn clearances) I used the new rotor inside the existing case. Hope that helps paint the picture.

Thanks again!
 
I dont think I ever get pressure on cranking. It provides enough to lubricate the cam etc but not to the extent that it registers pressure on the gauge. It's fine when it fires up.

So when you run it, is the cam dry or is there oil lubricating it? Take the filler cap off when idling for a very short time and see if there is oil splashing around. If so, you have pressure and the pump is ok but there is an issue with the sender or gauge. The next one is to earth out the positive feed to the sender and that will tell you if the gauge is working as it will go up to the top.

Its very unlikely that the pump shaft is not driving if the dizzy is working. It will only engage in 1 position vertically.
 
When I leave mine unused for over 4 weeks or so, it can take a while for the fuel to get to the carbs - so cranking for about 10 seconds or more is not unusual! (Poor starter I hear you say)! But, it does get the needle moving from off the chart to about zero so I figure it’s good for the car to have some oil flowing before it fires :p - but it shows that you can get some oil pressure while cranking.

As said already, often you find even when driving, the pressure on the gauge at idle drops to worryingly low levels. But if you open the oil filler cap while the engine is running, you see plenty of oil coming out of the cam holes. For perspective, when driving it sits between 1/2 to 3/4 across on the gauge depending on how much punishment I give it.

I did once have a change of underwear moment - while running in my new engine the pressure was low in normal driving and gradually dropped to below zero!!! Pulled over rapidly!! Same visual test showed all was good. A little head scratching later and I realised that the INSIDE of the bullet connector on the block sensor was green with corrosion. Once cleaned out with a needle file and bent for a tighter fit, it was just fine again. I would check that one thoroughly - 90% of the time that’s the culprit.
 
One other thought - I assume you have primed the pump and pre-filled the oil filter first before installing it - correct?
 
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