Strange oil pressure issue

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Map63Vette

Map63Vette

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So I noticed the other day when I nailed it in first gear on an onramp that my oil pressure warning light came on. It's not the typical dummy light as I can program the pressure range I want it to light at vs rpm, so I know it wasn't totally dropping pressure, but I wasn't logging at the time to look at it more closely. I noticed it did it again the other day, so today I made a point of trying to replicate the issue while logging to see what was going on. When running normally my oil pressure tends to be somewhere around 50-60 psi, maybe down to 40-45 when things get hot and the rpms drop, but nothing that would have my worried. However, looking at the log, as my rpm was climbing, my oil pressure was dropping away. Based on the way it builds then drops, I'm thinking maybe I'm just low on oil, but since it keeps some amount of pressure and doesn't fall all the way to zero I'm not quite sure what to think.

On the plus side, my traction control works really nicely. That first drop in pressure happens to correspond with the traction control pulling timing, but after the gear shift there wasn't any timing cut, it just seems to run lower pressure fairly steady.

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What oil pan? Does it have baffles? What’s the clearance of the pick up to the bottom of the pan?
 
lol, you point out that you might be low on oil so I'm guessing you would've check that before posting.
 
Milodon center sump steel pan with matching pickup and factory windage tray/gasket combo thing. I believe the pan has a "lid" over the center section to help keep oil in it, but it's been a long time since I looked inside it, so maybe I'm thinking of something else.

I think the part that confuses me is that the pressure goes down, but not completely away. I feel like a low oil issue would be showing drops closer to zero with a lot of spikes as it gets some oil, then an air pocket, then more. My gauge is damped some, but not all that heavily. I think I have it at 80% in the settings (100% being zero damping on the Megasquirt).
 
DionR said:
Bad sensor?
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It's pretty new, though I've known this particular Dodge style to fail before on my Viper I guess. Granted on that failure it just held an offset all the time, even with the engine not running.

It kind of reminds me of a story a guy with an original Hemi Cuda was telling me where it had a bad habit of pumping all the oil into the heads and it not draining back fast enough so it would starve itself, but I've never heard of that on a modern engine and my setup is all stock. I guess if it was a bit low I could see that.
 
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Map63Vette said:
It's pretty new, though I've known this particular Dodge style to fail before on my Viper I guess. Granted on that failure it just held an offset all the time, even with the engine not running.

It kind of reminds me of a story a guy with an original Hemi Cuda was telling me where it had a bad habit of pumping all the oil into the heads and it not draining back fast enough so it would starve itself, but I've never heard of that on a modern engine and my setup is all stock. I guess if it was a bit low I could see that.
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It was a complete shot in the dark on my part. Just an idea.

What about voltage spikes or drops? Could that cause errors in the sensor readings?

Only way I could see all the oil getting trapped up top is if the oil returns are all gunked up. And it seems like it would happen later on in a high RPM run not in first gear.

Only other thing I can think of is g-forces uncovering the pickup as other have asked. Seems like you have been working on the tune, maybe you have finally gotten it to that point? Add that if the on-ramp is up hill, maybe it is adding to the potential to uncover the pickup?

All just spit ball ideas.
 
DionR said:
It was a complete shot in the dark on my part. Just an idea.

What about voltage spikes or drops? Could that cause errors in the sensor readings?

Only way I could see all the oil getting trapped up top is if the oil returns are all gunked up. And it seems like it would happen later on in a high RPM run not in first gear.

Only other thing I can think of is g-forces uncovering the pickup as other have asked. Seems like you have been working on the tune, maybe you have finally gotten it to that point? Add that if the on-ramp is up hill, maybe it is adding to the potential to uncover the pickup?

All just spit ball ideas.
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I did notice it on some sustained high rpm running as well as I was trying to tune the upper end of my VE map, so thinking it must just be on the low side. I've never quite figured out why it seems to eat oil despite no smoke or particularly noticeable smell, but I have put this engine through a fair amount while I was learning and trying things. Guessing the hard hit in first on an onramp with a slight incline just leads to quicker onset of the pressure drop vs sustained high rpm on flat ground. I still find it strange that it doesn't show a full on loss when it sucks air, but I guess I should be thankful that it shows any pressure at all and that I can catch it sooner than later with my computer.
 
Put a mechanical gauge on it with a "Tee" before your electronic oil pressure sending unit.

Truck Palm Bay 2.jpg



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George Jets said:
Put a mechanical gauge on it with a "Tee" before your electronic oil pressure sending unit.

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Adding a T isn't easily done with the G3Hemi but they do have an alternate port, located on the side of the block, right above the temp sender.

Matt, I run "Glowshift" gauges and I'm pretty happy with them. I think the OP gauge is right round 55 bucks on zon, with sender.
 
Dantra said:
Adding a T isn't easily done with the G3Hemi but they do have an alternate port, located on the side of the block, right above the temp sender.

Matt, I run "Glowshift" gauges and I'm pretty happy with them. I think the OP gauge is right round 55 bucks on zon, with sender.
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I have an old truck cover on my engine, so I think it actually wouldn't be too hard to add a tee if I wanted to try. My temp sender port and the other one above it are currently being used to route to my remote oil filter, so that's not an option for me. Bigger issue would be getting a temporary mechanical gauge somewhere I could see it. I don't really want to run it through the firewall just for a quick test, but I guess I could probably tape one to the hood long enough to see.
 
Map63Vette said:
I have an old truck cover on my engine, so I think it actually wouldn't be too hard to add a tee if I wanted to try. My temp sender port and the other one above it are currently being used to route to my remote oil filter, so that's not an option for me. Bigger issue would be getting a temporary mechanical gauge somewhere I could see it. I don't really want to run it through the firewall just for a quick test, but I guess I could probably tape one to the hood long enough to see.
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If you have AN fittings, the mak a little adapter to go inline, that lets you thread in a sender.. I used one for my trans temp. just another option for ya
 
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