Recently I wanted to get oil pressure incorporated into my megasquirt. After getting everything wired up, I noticed odd behavior in that the pressure sensor would initially read 80 to 87psi until it 'warmed up' for a bit. After a while it would slowly start to pick up actual pressure, but swap between this 80 to 87 erroneous reading and the actual psi, then after a while, it would read the actual pressure and only very rarely have an intermittent 80 to 87psi. This process sometimes only takes a minute or two, but other times as taken over 30 minutes to completely get rid of the erroneous readings.

I checked all my wiring and everything seems right. I swapped the sender with a different one (also cheap Amazon sensor) and it exhibited the same behavior.

Looking for thoughts on if this is a wiring issue? Is there a better sensor I should use for this purpose? Should I try 'shielded' wire?

I'm wired to the 12v and ground circuits on the ECU meant for sensors. This is a real pain in the butt b/c I would like to use this as a trigger for a limp mode if i have unexpectedly low pressure, but because of these erroneous readings both at the 'start' and along the way, the limp mode gets triggered during normal conditions.

 

The cheap eBay sensors I used were 5v.

 

Most of these sensors are 5v, I’d double check the instructions, and only use cheap sensors for reference, not engine fail safes

 

Which sensors are they? Right after I posted, Amazon dropped off three at my house.

 

So when I said I checked all my wiring, I checked everything after the options connector. It turns out, the pin in the options connector was the culprit. Now every one of the sensors I bought from Amazon worked just fine.

 

I connected mine to an Arduino Uno R4 and tested with a syringe, they worked fine too. Plan is to send pressures via CAN to my telemetry. For me it doesn't have to be exact, I just want to know if I have fuel, oil, and water pressure in the right range and if not, turn on a light.

 

Sounds cool. My pain was that there is an oil pressure limp mode systemin the MS3 and if enabled and you get even 1 reading outside of range, it hits limp mode. So, yea, a bad connection will do some weird ****. All good for now though!