Just put in an atkins rebuilt engine under 200 miles ago. Had some initial problems with bad electrical contact on my oil pressure sending unit, (go figure) but got it reliably connecting again.

Problem is, that it reads perfectly normal oil pressures while cold, then drops to a hair above nothing while idling and maybe 45 psi at 3K rpm's after it warms up.

Would an oil pressure sending unit do that, or do I need to look elsewhere? Atkins seemed very reliable, I've heard nothing bad about them, but if I understood right, they reuse oil pumps, so I'm hoping it couldn't be that. I've always thought that with the mechanical oil pumps, they either work, or not anyway, but I could be a bit undereducated on that.

I read a similar post and someone said possible weak OMP to that person, but that makes little sense to me - I don't believe the sending unit is measuring oil presssure after the OMP, but again, there could be something I don't know there.

Any and all input would be remarkably helpful. This was my first personally done heart transplant, so I'm already a nervous wreck. Thanks in advance.

 

LOL, let me quickly edit myself by saying that sounded bad - I meant I believe Atkins uses rebuilt, not just resuses, oil pumps, unless you specifically order a new one. I didn't want to sound like I'm talking some crap about them, they did great by me in every way. I just don't know if it could maybe have a worn impeller that could somehow get by anyone.

 

It's not your OMP, I know that much. The OMP uses a stepper motor to drive the pump and the system monitors the stepper motor position to verify oil flow. No oil pressure reading on the OMP lines.

I'll let one of the experts discuss what's going on with your oil pressure. I will suggest that you start by cleaning the electrical connector really well. Sometimes on 3rd gens the sender connection isn't very good and it causes wild oil pressure readings.

 

First off, you need to make it clear what car you're working with. Reading from your profile, I'll assume you're working with an otherwise-stock 87 NA. Your OMP isn't like the FD, and you have an entirely mechanical OMP. What oil weight are you using? What's your idle speed set at? I've found with used bearings, that I often don't build good pressure with 10W30, but 20W50 does very well.

 

my bad - street ported but otherwise standard 87 NA - 10W40 oil used so far. I'd hate to have to move to 20W50 in the middle of an unusually cold michigan winter, and on my previous engine pressure reading tended to be pretty normal with 10W40, though stepping down to 10W30 was generally enough to read a little low. I have the older style mechanical OMP, by the way.

Also, yes, the connectors get messed up kind of easy on the 2nd gens too, and I had some initial issues with that. If you didn't mind Dielectric grease, you could eat off of it, currently, it's so clean, so it would have to be some sort of internal failure, not electrical, at least not at that connection.

 

That problem suggests the front cover o-ring has blown out. Classic symptom. But you must confirm the issue with another gauge. The stock gauge is only really good at reading "high" or "low". Just get a cheap mechanical gauge and test it.

 

I'll get on finding a non-stock gauge as soon as i'm financially capable, being a little tapped out after the engine replacement. As for the front cover O-ring though, shouldn't a leak there big enough to cause a pressure drop be visible? My engine seems perfectly dry.

 

The o-ring leaks internally.

http://www.mazdatrix.com/faq/oring.htm