Oil Pressure Issue at startup

[vairmech]

Just a little note, I have forgotten to put the plugs in the ends of the oil galleries, I still had 20 psi showing on the gauge at speed but at idle , yup, nothing!

You won't be the first one to do that!! One reason I always test a rebuilt engine BEFORE I install it in the vehicle.

Sad thing is I've done that more than once! But then I always pressurize the oil system on the stand before start up and with the top cover off so I can see the oil ooze out of the rods and mains.

[Lane66Monza]

OP should just start with a new switch and check wiring connections before jumping off deep end into gauges and plumbing. A loose wire grounding out could be causing the light issue

[vairmech]

After watching the videos, in the first one the oil pressure is not steady and that drop in pressure then going to about 40 psi, that would make me suspicious right off. In the second video yeah, there is no oil pressure! Obviously something going on there.

Without going back through all the posts was this engine rebuilt?

Here is what oil pressure should be like, at 25 seconds you get a good look at a steady oil pressure.

[SpyderMan]

Any ideas why the gauge on the filter would read 0psi while hot and in drive, 625rpm?

[SpyderMan]

Thanks Ken my post went up and then I saw your reply.

I rebuilt the motor in 2009. It has about 35k on it now. Last year I had it apart because my cam gear came loose, I caught it before it failed completely. While it was apart I looked at everything as far as crank and rod bearings and the looked very good and were still within specs but on the loose side. The car has 3k sense I put it back together.

Any chance a filter could cause problems? It must have some pressure because the light is out on the dash while the gauge says 0psi. I am going to get a reading at the sender.

[azdave]

Have you calibrated your gauge? I'll bet your engine is idling hot at 5-6 PSI but that the gauge just won't read that low accurately. I check my gauges when I'm trying to read any pressures in the 0-10 PSI range. On the workbench, I rig up an oil pressure gauge in parallel with a sphygmomanometer (blood pressure monitor gauge) because those are designed to read very low pressures accurately. I find them at thrift stores for cheap. 260mmHg is about the same as 5 PSI.

[SpyderMan]

This is a very cheap gauge so I do not know how accurate it is. I have a 0-15psi gauge somewhere I will find it and see what it says. What is the sender minimum pressure supposed to be?

[azdave]

This is a very cheap gauge so I do not know how accurate it is. I have a 0-15psi gauge somewhere I will find it and see what it says. What is the sender minimum pressure supposed to be?

Usually will trigger below 4-5 PSI but factory switches were set to 3 PSI from my understanding. I find these switches to have a pretty broad range from one to the next. If you have one that triggers at 6-7 PSI, it makes you think you have a problem when you really don't.

[Lane66Monza]

I found some where long time ago that the spec for the PS15 switch is that the switch opens (increasing oil pressure) at 3 - 7 psi. Which means it will turn on light at a lower psi that what it opens at (probably 1 - 2 psi lower.) I would rather have a switch open at 6 or 7 than at 3 psi, because at 3 psi on decreasing oil pressure it will have to be 2 psi or lower to give you a warning. At 7 psi, you get a little time to shutdown when light comes on at 5 psi.

With switches I tested in my garage, I kept them if they opened at 6 psi or greater. Lower opening pressure and they were scrapped.

[SpyderMan]

Can I test the oil pressure sender with air? I think I have something that would work if I can use an air pump.

[Lane66Monza]

Yes, but you need the right equipment. Hooking up to an air tank is not satisfactory, since those regulator gages can be 5 psi off at low pressures. You need a 15 psi calibrated gage and a separate regulator that you can meter that low pressure. I have a mini regulator set up and adapted to 1/8-27 id fitting to keep the flow & psi changes to match what the switch would see.

You need a 1/4" NPT - 1/8-27 NPT bushing in the outlet regulator. You need a 3 way 1/8-27 (2 female, 1 male) tee fitting off the Regulator outlet bushingto add the pressure gage to which I tape the switch threads and screwed the switch into the bushing. Pressure gage went into the port straight in line with outlet. I set the main air regulator to 40 psi max, when I check switches and only use a 3 ft off its regulator to my mini regulator. This setup gets repeatable switch test results.

1 8-27 bushing.jpg (26.94 KiB) Viewed 377 times

[SpyderMan]

Thanks Al, I will give that a try if my low tech solution fails. I have a hand pump that is with a 0-20psi gauge. I was going to adapt a Schrader valve to the pressure switch and see if that works.

[SpyderMan]

Update, I found my other gauge and it confirmed that the gauge I had been using is way off. Both pictures were taken at 625rpm in drive hot. I turned off the car long enough to switch places with the gauges to confirm the bad gauge. I also tested the pressure switch that was in the car and it indeed opened at 3psi, I bought a new one and it opens at 6psi. I will be installing the new 6psi pressure switch. Now that I am not freaked out by a bad gauge I am still getting pressure drop when I first start the car, I did not have my camera going but I could hear it. I will get another video with the lower pressure gauge when it has fully cooled and set over night.

Thanks again for all of the help so far.

[Lane66Monza]

Good to know you found switch on low side and got one on high side of spec. Gauge being off was a red herring but you got that fixed to keep from future troubleshooting issues.

Is that pressure drop with a vertical filter or the horizontal filter installation?

It would be good toknow if the filter position makes a difference.

[SpyderMan]

It seems to be the same with both, no change. I think I will try a filter and oil change soon and see if that makes any difference.

[Lane66Monza]

How long has it been since a filter change and whose filter did you use?